1. Oganic-Inorganic Perovskites
New generation of photoactive materials
absorber in solar cells and significant progress towards improved efficiency, fabrication and scale up process.
organic inorganic perovskite materials in photovoltaics as well as photoelectrochemical applications

2. power-conversion efficiency (PCE) of 22% for perovskite solar cells, similar to that of commercial crystalline silicon solar cells. (2009).
crystal structure, photophysical (optical-thermal properties) and surface morphology.
First basic unit of organometal trihalide perovskites (OTP) have been explored by H.L. Wells (1893), who already synthesized alkali-metal lead and tin halides
chemical formula CsPbX3 (X = Cl, Br or I) were analyzed after 64 years by the Danish scientist Christian Møller (1958).
After two decade, Dieter Weber (1978) replaced Cesium with methylammonium cations (CH3NH3+) and generated the first three-dimensional organic–inorganic hybrid perovskites.
In the 1990s, David B. Mitzi and his co-workers focused on perovskite crystal structure methylammonium lead halide, CH3NH3PbX3

3. tolerance factor (t) and octahedral factor (μ)
{t = (RA+ RX )/(√2(RB+ RX) μ
= RB/RX
0.81<t<1.11 and 0.44<μ<0.90
cubic perovskite structure
symmetric tetragonal or orthorhombic structures.

5. Developments in organometal trihalide perovskites (OTP)
Since photovoltaic's with a DSSC based on CH3NH3PbBr3 by Miyasaka and colleagues from Toin University reported an efficiency of 2.2%. In 2009, replaced 'Br' by 'I' and ceased efficiency was 3.8%, while stability was poor. In 2011, Nam-Gyu Park and co-workers from Sungkyunkwan University (SKKU) were able to achieve stability with PCE upto 6.5%. Subsequently, Park, Grätzel and other colleagues focused on demerits of electrolytes, introduced solid state hole transporting medium (HTM). A spiro MeOTAD (2,2‘,7,7‘-tetrakis(N,N-di-p-methoxyphenylamine)-9,9‘-spirobifluorene) HTM was effectively used in solid state dye cell in which HTM solute was used within nanoporous TiO2. The HTM improves the stability with increase stability in PCE 9.7%. In mid 2012, Henry Snaith and co-workers from Oxford University simultaneously exploited spiro-MeOTAD and used mixed halide in perovskite structure for better stability.

7. 'OTP is a class of materials that has quickly become the rising star of the solar cell world and would enable production of hydrogen fuel using sunlight ' as said by Sam Lemonick

8. Extremely optical absorption small effective mass of electron and hole dominant point defects – shallow levels grain boundaries

10. Metal −organic framework (MOF) structure of [C(NH2)3]-Mn(HCOO)3
Metal −organic framework (MOF) structure of [C(NH2)3]-Mn(HCOO)3.43In order to show the relationship with the halide perovskites, the oxygen atoms are drawn as red spheres in this figure; C, N, H, and Mn are black, sky blue, light pink, and cyan spheres respectively

11. ective Radii of Molecular Cations and Anions3
cant impact on the physical properties of the 3 3 4 ] − ) 2+ 2 ⟩ q 1
111 X 3 H R 3 + +
Note that the dimensionality discussed
NOH] ] 33 34 E
may sterically interfere with
= 182
was prepared as a light
100 E
= 174 3 4
and
X,eff 2 r
octahedra,
(pm) 32 ⟩
octahedra with the I NH −  “ 3 fi . →
organic framework (MOF) structure of [C(NH − 52 38 +1 m ⟩
direction of the 3-D perovskite structure
MOFs +1
inorganic perovskites, the q
tting this number of , A
= 12, 14, 16 −
perovskites. ⟩ +1 In
(I)Au(III)I
plane distortion of
two di
possibilities.
actions between organic cations and the inorganic substructure
nation.
long Au
lateral restrictions imposed by the metal halide layers, these can
provide a useful model sys
in general, and the hydrogen bonding schemes in particular, are
chain alkyl
because the coordination of the interlayer RNH
of known hybrid perovskites feature primary mono- or
important in the perovskite-derivative structures. The majority
subgroup of the perovskite derivative family, likely in part
the 3-D perovskite structure (top sections). (a) The family of ⟨ Tl
single inorganic [PbI
most readily accommodated in these structures. The inter-
bilayers.
phase. In all of these phases, charge ordering between Tl
diammonium cations. An interesting example involves long
Chemistry.
removal of the B-component from the inorganic framework
along a
the 3-D-parent ABX
allows for a remarkable structural tunability, i.e., from the
bonding schemes with the anionic substructure, which are
parent 3-D structure, based upon corner-shared BX
structure is cut into slices, the size restrictions, as outlined by
(RNH
superconductivity in CsTlX
recent experimental work,
components with a very di
bonding schemes. For example, perovskites containing Jahn
the compound can more speci
can be more or less rigid, which also in
TellerionssuchasCu
octahedral clusters.
Figure 4.
Table 1. E
all the way down to isolated, zero-dimensional (0-D) BX
Depending on the choice of metal, the inorganic framework
wherein the Au disprortionates into +1 and +3 states; that is,
important for determining the orientation and conformation of
from the 3-D parent compound ( BX
here refers to the connectivity of the corner-sharing BX
for the semiconducting
Chemical Reviews
the interlayer organic cations (see ref
obtained by taking
provide the
dimensional perovskite derivatives that feature di
subsections, we will review some of the recent reports on lower-
and, consequently, leading to a larger band gap. In the following
from the 3-D structure, including the well-known ⟨
3.1.
perovskites further follows from the theoretical prediction
in purely ionic interactions between
interact with the anionic inorganic substructure, but without the
Chemical Reviews
octahedra in the crystal structure, as conceptually excised
family, A
the fact that the dimensionality of the inorganic framework is
reduced by removing the metal
rest of the organic molecule interfering with the inorganic
components
The
thought of as intergrowth compounds with a general formula of
described as square planar for Au
brown powder that adopts a double cubic perovskite
around Au(I) and Au(III) can perhaps more accurately be
[PbI
fertile
For example, in two-dimensional (2-D) layered derivatives of Tl BX
the perovskite framework.
structures with varying physical properties.
The presence of ammonium cations leads to various hydrogen
are remarkably fl
section 3
the perovskite structure, there are no known restrictions for the
decrease under pressure, no evidence of a phase transition to a
interlayer
restrictions are not applicable altogether, as MX
isolated and can readily shift in relative position. This structural Tl
obtaining a superconducting phase, has been observed so far. In
ing lower-dimensional or 3-D defect crystal structures (see
Chemical Reviews
structure, whereas orange crystals of CsTlCl
known organic
comparison to these inorganic systems, there are only a few
dimensional perovskites, there are still other important
Figure 6.
in alternating long and short B-X bonds and the prospects of (6
crystallographic center of the metal halide octahedra, resulting
generally gives rise to a shift of the metal atom away from the
stereochemically active lone pair (or “
(272
of a targeted perovskite-derived structure.
the tolerance factor for the 3-D structures, are gradually lifted.
parameters to consider for the successful design and synthesis
Figure 5.
perovskite derivatives feature mono- or diammonium cations,
yielding the general formulas of (RNH
bonding/coordination preferences for the metal ions involved,
which can impact the structural chemistry. For example, in the
related inorganic Cs A
110
100
Adapted from ref
exibility and tunability of the dimensionality provide a rich and + 2+ 3+ s
While the size restrictions may be relaxed for the lower
In addition to size and charge, there are also the details of the ”
Dabconium [C
3-Pyrollinium [NC
Tetramethylammonium [(CH
Azetidinium [(CH
Tropylium [C
Ammonium [NH
Dimethylammonium [(CH
Formamidinium [NH
Piperazinium [C
Hydroxylammonium [H
Hydrazinium [H
Imidazolium [C
Ethylammonium [C
Guanidinium [C(NH
Methylammonium [CH 6 4
,Ge
) ions that are isoelectronic to Bi
, where here
must contain terminal functional groups that can ionically
octahedral coordination, leading to structural distortions of ⟨
(i.e., delocalized charge) state, which would be required for ⟩ ⟩
was con ⟨ 2
100
-, and
-oriented perovskites currently represent the richest
C) the melting transition of
100 ff ⟨ 3 31 “
Fluoride
Bromide
Iodide I
Formate HCOO
100
erent polymorphs, a tetragonal
playground ′ 49
sheets that are separated by a monolayer of aromatic biimidazolium (C
··· 2
Structures of the organic cation bilayers in (C
Schematic representation of the derivation of the lower dimensional organic
,Sn ). A A
In another example, the lone pair ⟩
Combined skeletal (top) and polyhedral (bottom, shaded) representation of the crystal structure of (C −
I contacts nominally completing octahedral coordi- “ b n
-Oriented Perovskites
-oriented perovskites are obtained by the ordered ff ⟩ 6 ⟨ 51 A ‑
Anion “ −
Radii calculated from the single crystal X-ray data. 1 .
110 R 30 B 2+ ”
in the ABX fi − “ ⟨ B fl q ”
The advantageous feature of the hybrid perov- B ,
rmed to exist. Although resistivity was found to 7
,Pb X 31
at, with a Pb
Cation 3 −
cation length and, in the 0-D derivatives, size n H ⟩ ”
groups ( 3 H 3
-oriented family, A 4 3 N 7
inorganic mixed-valent perovskites, all featur- q H n
N-NH 4 4 ]+ +3 α
and ] 2 “ 2
Interest in the mixed-valent metal halide ⟩ n 4 2+ 22 12 + ) 4
layers from along the N ” H +1 9
, is formed by excising along the
-oriented families as well as more exotic 2 ] =2 H N , NH
,Sb − 5 2 2 10 2 ” 8
, formed from the two end members: i.e., ] ] )
for the preparation of interesting crystal −
(CH)NH + ] 2 5
with permission from The Royal Society of + 2+ 3 ] NH 3 3 2 2 “ ]
represents an organic functional group.
sheet is shown, viewed along the 2+ NH ] 2
Au(I)Au(III)I X . + 3+ ]
Figure 5 +
and 2-D-layered (RNH 3 3 ” 3 )
, and Bi ]
. Most of the known layered (2-D) 22 3 −
inorganic 2
structure. Alternatively, they can be + NH 3 + 3 I , )
, which features Tl − + 4 2 N] ] ff
feature highly distorted CuX
CsTlF
Pb angle of − 2 + ]
erent set of electronegativities 37 “ +
tem for the study of lipid fi B
). Subject to the constraint of
cally be expressed as Cs 3+ ′ m ”
In the perovskite structure, a
Figure 4 3+ A
, which results in an increase m 3
halide perovskite CsAuI 3+ ff B 6
and linear for Au
ective radius ⟨ m I
and Bi X s ) 4/
the primary bonding ff
-orbital hybridization) fl β 2
ective radius 10 BX m
uences the hydrogen m ⟩ “ C.
). As the perovskite A s
direction of the parent structure. (b) Cuts along the
The organic cation 2
, which includes 1-D chain (
and a cubic 51
220
196
129
136 ” 5+ 10
were obtained in
electrons on B =
or (NH +
Reprinted with permission from ref 3
electron pair, giving rise to a coordinated structural .
distortion, as has been discussed for the low temperature phase ff
transitions observed in hybrid perovskites can be di
the B-metal cation, the temperature and the order of the phase
Depending on the length of the organic chain and the nature of
these transitions through a variety of spectroscopic techniques.
skites is that, unlike free lipid bilayers, since the organic cations s 3 3
erent.
SnBr
active
of CH
are anchored to the inorganic perovskite lattice, the phase 2
directional hydrogen bonding of the organic cation can also
couple through intervening halogens to the steriochemically
transitions are solid-to-solid, which allows investigations of
long chain organic cations undergo +1 NH 3 n 2 (C n H ) 2
= 12, 16 and 18) above the melting
transition are noted to be similar to that of n n (
PbI 4
Raman spectra of 51 “
melting transitions ” 36
ammonium functional group, the hybrid perovskites containing −
addition to the regular dynamic rotational disordering of the
as a
function of temperature, which are characterized by an
disorder results in the nonuniform distribution of the
orientation of the chains, and consequently, in the increase of
the interlayer lattice parameter.
This large increase in gauche conformational 50
increased conformational disorder of the methylene units of
the alkyl groups. 49 2
no metal
a terminology that is misleading, since there are −
carbon bonds or direct linkages between metals and
referred to as
organic ligands. These structures can more accurately be
perovskites ”
yield a 3-D organic
chemical combinations that can −
inorganic perovskite. “
Note that the perovskites based on metal halide frameworks
organic-inorganic or ff
erent cuts − 45 2
with 43 ⟨
However, organic
hybrid
inorganic perovskites with direct bonding -,
100
between a metal and an organic ligand do exist, ” X
-alkanes in the 2
. The 4 ) BX 39
Y),
distortions: for example, AMnO −
(A = Pr, Nd, Dy, Tb, Ho, Er,
cations is 3 + 3 6 “ , B ” “
, and ” A 41 40 , 42
number of
charge, and chemistry constraints, there are only a limited
On the other hand, a number of transition ) 4 ) 2+ N 8 6 H
dications.
In the right half of the Fm c 3 m fi
gure, the structure of a Fm 3 H 8 6 1+
. Copyright 2010 American Chemical Society.
, with N 4 + m
and
, which features
)PbI 4
-axis (i.e., top down), with the organic cations removed for clarity. The inorganic layers
.Ina 2 , 3
Au- of
, and the out-of-
Review
DOI:
4596
4562 −
2016, 116, 4558
/acs.chemrev.5b00715
Chem.Rev.
94.83 − 2 s
) and Tl 3+ 3
in BaBiO
, and contain regular PbI −
I angles of 87.70 Pb − 6 (6 51
ferroelectricity.
and 18). 51
Snapshots of the simulated structures above and , n 4 (
below the melting transition for (C 18 ) 2 36 NH H 37
PbI 2
fully reproduce the experimental data, except for the detailed
transition temperatures, for (C
Molecular dynamics (MD) simulations were used to success- 50
melting transition, the alkyl chains of the bilayers are liquid-like
in two dimensions between adjacent inorganic layers. n H 3
,two NH
For organic 2 n
PbI 4 H 37 18 34
for example, the inorganic , NH 3
, obtained using molecular dynamics simulations, below (142
C) and above 4
PbI ) 2 52
(B = Pb, Sn),
Recently, several examples of perovskites containing non-
primary ammonium cations have also been prepared. In .
Figure 5
are
provided in (C 6
)BI 4 4 N H 8
molten state. These spectra support the idea that, above the ”
control over the fi
nal structures and properties.
uence on each other, allowing a certain degree of fl
organic cations and the anionic inorganic framework have
templating in
As mentioned above, lower-dimensional derivatives of the
perovskite structure can be obtained by making slices along
stoichiometry are among the most in fl
uential parameters on
The choice of the organic cation(s) and the reaction
erent crystallographic directions in the parent compounds. di ff
by allowing organic molecules to tilt. In summary, both the
the structure can accommodate
organic molecules that are too large (in terms of their width)
may cause steric hindrance with adjacent organic molecules,
which in turn would render impossible
dictates the presence of a certain concentration of cations, and
electron counting schemes. The charge balance requirement
halides from four adjacent corner-sharing octahedra. This is
important both from the perspective of hydrogen bonding and fi
A,eff
by the inorganic substructure 
i.e., much smaller than the area provided 
cations into the targeted perovskite framework. However, if
they are too narrow
the orientation of the resultant inorganic frameworks. It is
important to note that the dimensional reduction discussed Sn n I 1 − ) n 3 n
)CH 3 ∞ a
perovskite ( n 3 NH
lowered. This is best illustrated by the example of (C 4 H
typically increases as the dimensionality of the structure is
compounds. For example, the band gap of the compounds
here has signi fi 9 NH
(CH 3 - 2 3 )
ned by the terminal fi 3 ) 2 ]-
Mn(HCOO)
In order to show the relationship with the halide 43 −
Metal b
339 r
(pm)
Figure 3. 26
perovskites, the oxygen atoms are drawn as red spheres in this fi −
2016, 116, 4558
Chem.Rev.
4596
4560 6 6
/acs.chemrev.5b00715
DOI:
C, N, H, and Mn are black, sky blue, light pink, and cyan spheres,
gure;
octahedra are 6
Review
respectively.
333 b fl
exibility for the interaction
with interlayer organic cations.
octahedra that enable greater 6 −
146
For the diverse family of 2-D perovskite frameworks,
although there is no de fi
t into an area de
width, which must
the interlayer organic cations, there is a restriction for the fi
nitive restriction for the length of
216
217 )-
292
278 3
RNH
322 3
274
272
for details).
217
250
253
272
258 NH
compounds, for which the parent 3-D
organic 3
4596 −
4561 − m
> 1) members. (c) The
Chem.Rev.
compounds provides a direct link between the traditional
= 1) and 2-D layered (
2016, 116, 4558 (
In this example 3 ”
: a widely expanding 3
class of compounds with potential application in catalysis, gas
where M = Mn, Fe, Co, Ni, Cu, and Zn. “
metal
inorganic perovskites based on metal halides and 43 −
organic frameworks or ⟨
/acs.chemrev.5b00715
= 1) and 2-D layered (
) the guanidinium cation occupies the
ABX q 3
site in the ” ⟩ ⟨
direction of the 3-D parent, and features 0-D isolated cluster ( “ +
perovskite framework and the formato anion takes the
role of the X
This family of
-oriented
Review
111
DOI:
Figure 3 45
anion (this time an organic anion). Examples of −
analogous structures with the guanidinium cation replaced with
other organic amines are also known. 44
111
storage, puri
semiconductor. 48
is a large band gap 4
SnI
In simple terms, this can be rationalized by
extended family of lower-dimensional perovskites, which then ff
erent cuts of
inorganic perovskites (lower sections) from di
structure described above has fairly rigid
structural constraints, one can explore within a broader 2 )
semiconductor (even yielding semimetallic character), whereas
the
is a dopable small band gap 3
SnI n
= 1 compound (C NH 3 9 H 4
cation, and separation. 3
are
INORGANIC
PEROVSKITES “ 3 −
3. LOWER-DIMENSIONAL ORGANIC
110 46 ⟨ , 47 ⟨ X 3 )
-oriented layered perovskites with a general formula of (RNH ⟩
100 X 2 1 B
While the ABX 6 A
Schematic representation of the derivation of the lower dimensional organic−inorganic perovskites (lower sections) from different cuts of the 3-D perovskite structure (top sections). (a) The family of ⟨100⟩-oriented layered perovskites with a general formula of (RNH3)2An−1BnX3n+1 are obtained by taking n layers from along the ⟨100⟩ direction of the parent structure. (b) Cuts along the ⟨110⟩ direction of the 3-D perovskite structure provide the ⟨110⟩-oriented family, A′2AmBmX3m+2, which includes 1-D chain (m = 1) and 2-D layered (m > 1) members. (c) The ⟨111⟩-oriented family, A′2Aq‑1BqX3q+3, is formed by excising along the ⟨111⟩ direction of the 3-D parent, and features 0-D isolated cluster (q = 1) and 2-D layered (q > 1) members. In each of these layered structures, the perovskite framework is separated by a layer of typically larger organic cations. 2+ 2 3 +2 3
metal ions are also impacted by Jahn
Teller and related 3
Given the substantial size, , Br .
and KCuF Cs Au T
and organic cations are often referred to as
organometal +
Thiazolium [C H
NS]
320 ” ” “ “ 6 14 2
prototypical examples including [C(NH )
]M(HCOO) ,
Chloride
181 n n n
> 1) members. In each of these layered structures, the perovskite framework is separated by a layer of typically larger organic cations.

12. Structures of the organic cation bilayers in (C18H37NH3)2PbI4, obtained using molecular dynamics simulations, below (142 °C) and above (272 °C) the melting transition of Tm = 182 °C.51 Reprinted with permission from ref 51

15. (a) Electronic band structure of MAPbI3 , adopted from density-functional theory calculations presented in References 40 and 45. Colored upward-pointing arrows represent allowed photoinduced electronic transitions. The lowest CB (CB1) is the spin-orbit SO band, whereas the higher-lying CB2 comprises HE and LE states, according to References 40 and 45. The dashed blue arrows indicate the partly dipole-allowed transitions VB2 → CB1 and VB1 → CB2 at the R point. (b) Absorption spectrum showing that a continuum of electronic transitions between the R and M valleys leads to strong absorption across the visible range (46). Relaxation toward the R valley gives rise to a photoluminescence peak near 1.6 eV arising from CBM1 → VBM1 transitions at the R point. Abbreviations: CB, conduction band; CBM, conduction band minimum; HE, heavy electron; LE, light electron; SO, split-off; VB, valence band; VBM, valence band maximum.

16. Schematic diagram indicating recombination mechanisms active in organic-inorganic metal halide perovskites. (a) Trap-assisted recombination is a monomolecular process involving the capture of either an electron (as shown) or a hole in a specific trap state (e.g., defect). (b) Bimolecular recombination may occur between electrons and holes, from either the relaxed state (CBM → VBM) or states higher in the band. (c) Auger recombination is a higher-order process involving at least three particles. The energy of an electron (or hole) is here transferred to another electron (or hole) to allow nonradiative recombination with a hole (or electron). As indicated, all processes have to satisfy energy and momentum conservation. Abbreviations: CB, conduction band; CBM, conduction band minimum; VB, valence band; VBM, valence band maximum.

18. SUMMARY POINTS
1.Hybrid organic-inorganic metal halide perovskites exhibit interesting structure-property relationships deriving from their propensity to undergo structural transformations with relative ease.
2.The exciton binding energy Eb appears to be a function of temperature as a result of the strong temperature dependence of the dielectric function. At room temperature, Eb is in the range of a few milli-electron volts to at most a few tens of milli-electron volts, in accordance with the presence of a free-charge-carrier population.
3.Charge-carrier relaxation dynamics within the first few picoseconds after excitation are marked by thermalization, cooling, and many-body effects. It remains to be explored whether extended hot charge-carrier phases can be utilized in photovoltaic devices that exceed the Shockley-Queisser limit.
4.Trap-assisted (monomolecular) charge-carrier recombination is mostly nonradiative and highly specific to material processing, yielding associated lifetimes from nano- to microseconds. Traps in hybrid lead halide perovskites appear to be mostly shallow (approximately tens of milli-electron volts), arising, for example, from elemental metal, halide, or organic vacancies, and may be present in higher density near interfaces and grain boundaries.
5.Bimolecular charge-carrier recombination is predominantly radiative and exhibits rate constants that defy the Langevin limit by many orders of magnitude.
6.Nonradiative Auger recombination is significant for charge-carrier densities corresponding to the threshold for amplified spontaneous emission. Rate constants show a strong specificity to crystal structure, opening the possibility for the design of materials with low Auger rates from first-principles calculations.

19. In summary, organic-inorganic metal halide perovskites have proven to be a fascinating material system to investigate. Few materials show such inherent flexibility in terms of compositional and structural modification, yet allow for excellent optoelectronic properties, including high charge-carrier mobilities, strong optical absorption, and low trap-assisted recombination rates. Whether perovskite photovoltaic cells will become competitors to current silicon technology, the lessons learned from investigating their photophysics will serve as highly valuable guidelines on how to design effective light-harvesting and light-emitting materials.

20. Reproduced from Chem.Soc., 2025,6,3430

21. Reproduced from Chem.Soc., 2025,6,3430

22. Reproduced from Chem.Soc., 2025,6,3430;supplement

26. Nat. Rev. Mater. doi:10.1038/natrevmats.2015.7
Figure 2 Electronic structure and closely related physical properties of HOIPs
Panel b adapted with permission from REF. 49, American Chemical Society. Panel c from REF. 63, Nature Publishing Group. Panel d adapted with permission from REF. 31, Royal Society of Chemistry. Panel e adapted with permission from REF. 74, American Chemical Society. Panel f adapted with permission from REF. 76, American Chemical Society
Brenner. et al. (2016) Hybrid organic–inorganic perovskites: low-cost semiconductors with intriguing charge-transport properties
Nat. Rev. Mater. doi: /natrevmats

32. Organic-Inorganic Perovskites
1st October,2016 (contributed by Nilesh Manwar)

33. Organic-Inorganic Perovskites
Outline:
Background
Past History
Recent Development
Why Organic Inorganic Perovskites?
ORGANIC-INORGANIC PEROVSKITE STRUCTURES
Chemical composition and crystal structure of ABX3
Optoelectronic properties
SYNTHESIS AND CRYSTAL GROWTH
Future challenges

34. Background : Solar cell History:
1839: Alexandre­ Edmond Becquerel son of physicist Antoine Cesar Becquerel and father of physicist Henri Becquerel
1873: Willoughby Smith, an English engineer , discovered the
photoconductivity of selenium
1883: American inventor Charles Fritts made the first solar cells from selenium
1940 Russell Shoemaker Ohl, a semiconductor researcher at Bell Labs. Patented with 1% Eficiency
1953 Daryl Chapin, Calvin Fuller and Gerald Pearson
April 25, 1954: Bell Labs Demonstrates the First Practical Silicon Solar Cell

35. Past History of Organic-Inorganic Perovskites:
H.L. Wells (1893) synthesized Alkali-metal lead and tin halides
Christian Møller (1958) first crystallographic studies that determined that caesium lead halides had a perovskite structure with the chemical formula CsPbX3(X = Cl, Br or I)
Dieter Weber (1978) replaced caesium with methylammonium cations (CH3NH3+)to generate the first three-dimensional organic–inorganic hybrid perovskites
Mitzi, D. B. Methylammonium lead iodide, CH3NH3PbI3, has both interesting optical and electronic properties that have been actively investigated during the past two decades
Short History:
(Ref: Wells, H. L. Z. Anorg. Chem. 3,195–210 (1893)
) yet the first crystallographic studies that determined that caesium lead halides had a perovskite structure with the chemical formula CsPbX3(X = Cl, Br or I) were only carried out 64 years later by the Danish scientist Christian Møller. He also observed that these coloured materials were photoconductive, thus suggesting that they behave as semiconductors.
In 1978, Dieter Weber replaced caesium with methylammonium cations (CH3NH3+)to generate the first three-dimensional organic–inorganic hybrid perovskites
Weber, D. Z. Naturforsch. 33b,1443–1445 (1978).
Weber, D. Z. Naturforsch. 33b,862–865 (1978)
Methylammonium lead iodide, CH3NH3PbI3, has both interesting optical and electronic properties that have been actively investigated during the past two decades Ref: Mitzi, D. B. Synthesis, Structure and Properties of
Organic–Inorganic Perovskites and Related Materials:
Progress in Inorganic ChemistryVol. 48 (ed. Karlin, K. D.)
1–121 (J. Wiley & Sons, 1999).
6. Baikie, T. et al. J. Mater. Chem. A 1,5628–5641 (2013).
7. Umari, P., Mosconi, E. & De Angelis, F. Preprint available at

36. Recent Development in PSC
Korean Research Institute of Chemical Technology (KRICT)
National Renewable Energy Laboratory (NREL)
Sungkyunkwan University (SKKU)
E´cole polytechniquefe ´de´rale de Lausanne (EPFL)

37. Why Organic Inorganic Perovskites?
In the Sept. 26 Science, Grätzel’s group describes a device that uses sunlight to split water into oxygen and hydrogen gas with 12.3 percent efficiency. That figure puts the device above the 10 percent benchmark for useful solar­to­hydrogen conversion. Hydrogen holds promise as clean fuel to power cars or produce electricity.
yields a water-splitting photocurrent density of around 10 milliamperes per square centimeter, corresponding to a solar-to-hydrogen efficiency of 12.3%.
Mechanism; circuits
Ref: Luo, J.; Im, J.-H.; Mayer, M. T.; Schreier, M.; Nazeeruddin, M. K.; Park, N.-G.; Tilley, S. D.; Fan, H. J.; Gratzel, M. Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts. Science (80-. ). 2014, 345, 1593–1596.

38. ORGANIC-INORGANIC PEROVSKITE STRUCTURES
A. Three-Dimensional Systems
B. Layered (100) Oriented Perovskites
1. Transition Metal Halides
2. Group 14 (IVA) Metal Halides
3. Rare Earth Metal Halides
C. Structural Transitions
D. More Complex Organic Cations
E. Polymerized Organic Layer
F. Multilayer Perovskite Structures
G. Layered (1 10) Oriented Perovskites
H. One-Dimensional Systems
I. Zero-Dimensional Systems
J. Summary of Structure

39. Interaction types between the organic and inorganic components
In ionic compounds, the organic component is an intimate part of the overall structure and in fact the structure depends on the organic ion for overall charge neutrality. In contrast to the previous group, these compounds have specific stoichiometries, with the organic ions occupying well-defined sites in the crystal lattice. Furthermore, the ionic bond length is substan-tially smaller than typical van der Wads distances, providing the potential for a stronger interaction between the organic and inorganic components. These compounds are mainly formed in divalent transition, main group,
and rare earth metal halides with one (1D)-, two (2D)-, or three-dimen- sional (3D) perovskite and related structures

40. Basic structure of Perovskites:
Usually have stoichiometry of AMX3
t = (RA + R,) /(RB + R,), 0.8 ≤ t ≤ 0.9
X is an oxide or halide anion such as Cl, Br and I.
M refers to a metal cation with a coordination number of 6.
The MX6 octahedra share corners and A is usually a large cation that fills the cuboctahedral holes with coordination number of 12.
A can be Ca, K, Na, Pb, Sr, other rare metals.
CrystEngComm, 2010, 12,

41. Organic–inorganic Hybrid Perovskites
First three-dimensional organic–inorganic hybrid perovskite, discovered by replacing caesium in CsPbX3 (X = Cl, Br or I) with methylammonium cations (MA = CH3NH3+) by Dieter Weber, in 1978.
CH3NH3PbI3 is most common used materials for making high efficiency perovskite solar cells.
CH3NH3PbI3 is a semiconducting pigment with a direct bandgap of 1.55 eV with absorption coefficient as high as  104–105 cm−1
Methylammonium (MA)
JACS, 136, 622, 2014

42. Basic structure of organic-inorganic perovskite
The basic building component of the organic-inorganic perovskite family is the ABX3 perovskite structure
Taking, for example, a system with one of the largest possible values for R, + R,, B y Pb and X = I [R,, = 1.19 A and R, A (5?)], and using t = 1, we find that R, should not exceed approximately 2.6 A. Given that C-C or C-N bond lengths are of order 1.4 A, only the smallest organic molecules-those consisting of two or three atoms (excluding hydrogens) should fit into the structure.
Based on these considerations, the methylammonium cation is expected to be an appropriate choice for the 3D perovskite structure. In fact, the compounds CH~NH~MXJ, with M - Sn and Pb, and X = C1, Br, and I, have all been synthesized and structurally characterized (60-69). Each of these systems adopt (as the highest temperature phase) the cubic perovskite structure. For the lead(I1) compounds, the cubic lattice constants vary from a = 5.657(2) A (X = C1) and a = 5.901(1) A (X = Br), to a = (4) A (X, I) (66, 67). The corresponding tin(I1) compounds have the similar lattice constants, a = 5.89 A (X - Br) and a = 6.240(1) A (X = I) (60, 63). Since the symmetry of the free methylammonium cation does not agree with the Oh site symmetry for the A cation of the cubic perovskite structure,the organic cation must be orientationally disordered in the high-temperature phase. In fact, for cubic CHJNH3PbX3, with X = C1, Br, or I, nuclear
magnetic resonance (NMR) and nuclear quadruple resonance (NQR) spectroscopies demonstrate that the methylammonium cation undergoes rapid isotropic reorientation (64, 65, 67). Upon cooling, the structures distort to
lower symmetry (Table I)
The compound CH~NH~EUI~ has also recently been prepared and at room temperature is isostructural to the tetragonal (room temperature) CH3NH3Pb13 structure, with the lattice parameters, a = 8.917(2) A and c = (4) A (70). As of yet no low-temperature studies have been performed on the europium(I1) material, but the succession of phase transitions is likely to be similar to those observed in the lead(I1) and tin(I1) systems. In addition, the methylammonium cation has been replaced by the larger formamidinium cation in the tin(I1)-based system, NH2CH=NH2SnI3, yielding a room temperature cubic perovskite structure with the lattice constant, a = 6.316(1) A,
Methylammonium (MA)
JACS, 136, 622, 2014

43. Organic–inorganic Hybrid Perovskites cont.
The unit cell parameter 𝑎 increases from 5.68 to 5.92 and to 6.27 Å as the size of halide increases from X = Cl to Br and to I, respectively.
The large size and aspherical shape of MA cause distortion in network and drives several phase transitions by decreasing T.
For T <160 K orthorhombic, K<T< K tetragonal and T > K cubic.
Phys. Rev. B 90,

44. Three-Dimensional Systems

45. Ruddlesden-Popper compound e.g. K2NiF4 (or La2Cu04)
Layered (100) Oriented Perovskites
(R-NH3)2MX4, where R- NH3 is an aliphatic or single ring aromatic ammonium cation
Ruddlesden-Popper compound e.g. K2NiF4 (or La2Cu04)
these materials are organic-inorganic, but not organometallic – following the IUPAC definition – as there is no
direct bond between a metal and carbon atom.
The basic structures of 2D organic–inorganic perovskite with bilayer (a) and single layer intercalated organic molecules

46. 1. Transition Metal Halides
I. PABST, H. FUESS AND J. W. BATS (1986)

47. 2. Group 14 (IVA) Metal Halides
Schematic of the perovskite crystal structure with respect to the A, B and X lattice sites.

48. 3. Rare Earth Metal Halides
(C4H9NH3)2EuI4

49. F. Multilayer Perovskite Structures
The <100>-oriented hybrid perovskite series with general formula of (RNH3)2An1MnX3n+1. The thicknesses of inorganic slabs increase and toward 3D structure with increasing n
Schematic representations of hydrogen-bond styles between NH3+ heads with an inorganic
framework.

50. Crystallographic Data

51. Schematic representation of the <110>-oriented family of layered hybrid perovskites with general formula of A20AmMmX3m+2. Here, A is CH3NH3,A0 is NH2C(I)]NH2+

52. The molecular structure of organic component of API$2HBr (a) Crystal structure of perovskite API$PbBr4viewed down the a axis of <100> (b) and the corresponding ball and stick model (the red lines represent hydrogen bonds) (c).

53. Schematic representation of the <111>-oriented family of layered hybrid perovskites,A20Aq1MqX3q+3.
Crystal packing structure of 0D hybrid perovskite (C4H8N2H4)2PbBr6$2H2O [(H23-AMP)2PbBr6for abbreviation]

54. Schematic of the ordering of molecular dipoles in the presence of an external electric field, as well as the four regimes in the dielectric response from lowest frequency

55. Summary of Structure

58. Lattice parameters (A0)
Structural phase transformations for CH3NH3PbX3 (X= Cl, Br and I) X
Phases
Temperature (K)
Crystal System
Space group
Lattice parameters (A0) a B c Cl α
>178.8
Cubic
Pm3m
5.675 - β
Tetragonal
P4/mmm
5.656
5.6 γ
<172.9
Orthorhombic
P2221
5.673
5.628
11. 08 Br
>236.9
5.901
I4/mcm
8.322
11. 83
5.894
5.8 δ
<144.5
Pna21
7.979
8.580
11. 8 I
>327.4
6.328
8.855
12. 6
<162.2
8.861
8.581

59. PROPERTIES 1. Band Gap Engineering Band gap deformation potential
Temperature-dependent photoluminescence indicates a decrease in band gap with decreasing temperature (lattice
contraction) from 1.61 eV at 300 K to 1.55 eV at 150 K
Calculated natural band o↵sets of CH3NH3PbI3 and related materials based on density functional calculations (with quasi-particle corrections). Interfacial or surface electric dipoles (or quadrupoles) are not considered here.

60. Band Gap Tuning
Bandgap tuning is required to extend the absorption to longer wavelengths without sacrificing the absorption coefficient.
Changing in any of A, M and X in AMX3 changes the bandgap
The bandgap also can be tuned in between 1.55 eV and 1.17 eV by varying the ratio of lead to tin
FA: formamidinium HC(NH2)2+  
Small Volume 11, Issue 1, pages 10-25, 30 OCT 2014 DOI: /smll

61. 2. Photoluminescence
Room temperature absorption coefficient as a function of wavelength (A) for (a) (CH~NH~)JP~I~.~H$~, (b) [r\;H?C(I)=NH213PbI5, (c) (C~H~~NH~)~P~IJ, and (d) CH3NH1PbIj. These systems consist of OD. ID, 2D, and 3D extended inorganic networks of corner-sharing PbI6 octahedra.

62. 3. Electrical Transport
4. Electroluminescence

63. SYNTHESIS AND CRYSTAL GROWTH
A. Self-Assembling Structures
B. Solid-State Reactivity and Melt Processing
C. Solution Chemistry
1.Simple Organic Cations
2. Less Stable Metal Oxidation States
3. More Complex Organic Cations
4. Gel Techniques and Layered Growth
5. Multilayer Structures
6. Cyanamide Chemistry and the (1 10) Oriented Compounds
D. Polymerization Reactions
E. Thin-Film Growth
1. Spin Coating
2. Thermal Evaporation
3. Dip Coating

64. A. Self-Assembling Structures
direct solid-state reaction between the organic ammonium salt and a metal(II) halide.
“more complex” structures through the interaction of a number of different types of forces between the constituents of the structure (covalent, ionic, hydrogen-bonding, van der Waals, etc.). In general, self-assembling materials can be made simply, by techniques such as the Langmuir-Blodgett process

65. B. Thin-Film Growth Preparation Method There are two common methods:
one step coating: spin-coating a mixed CH3NH3I and PbI2solution
two-step coating: spin-coating CH3NH3I after coating with PbI2
Small Volume 11, Issue 1, pages 10-25, 30 OCT 2014 DOI: /smll

66. I. Spin Coating
Room temperature X-ray powder patterns for spin-coated thin films of (C~H~NH~)~P~IX~, where (u) X CI, (b) X : Br, and (c) X I. 'The X-ray reflection indices are given above the data for X = I, and are the same for each sample

67. 3. Dip Couting
Room temperature X-ray patterns for (N) an array of sheet-like (C6115C?H4NH3)?Phi3 crystals, prepared using a solution chemistry technique, and (h) a (C~HgC?€ijNH3)2PbI~ thin film. prepared by dipping a PbI? thin film into a 2-propanoI/toluene solution of 77 mM phenethylammonium iodide for 10 min

68. Electrodeposition:
Pb+2/Pb ; E = −0.13 V
Sn+2/Sn ; E = −0.14 V

69. Future Challenges of organic inorganic Perovskite
Synthesis and development in organic inorganic perovskites to improve light harvesting properties of mixed oxides.
Increasing air and temperature stability
Replacing toxic Pb with a greener element
Is AMX3 (perovskite structure) the best stoichiometry? Have we tried other structures?
Thank you

70. Acknowledgments: Dr. Sadhana Rayalu Dr. Nitin Labhsetwar
Dr. Amit Bansiwal
Dr. G. Sarvanan
All EMD Friends
CSIR-TAPSUN Project for funding

71. B. Solid-State Reactivity and Melt Processing
Fortunately, it is found that organic ammonium halides often undergo solid-state reaction with metal(II) halide salts at low temperatures, sometimes even showing appreciable reactivity at room temperature.
A more quantitative examination of the solid-state reaction between the alkylammonium halides and metal(I1) halides- thermal Analysis
Simultaneous TGA and DTA scans for ((1) C3H9NHz.III and (h) (CjH9KHs)2Eul4 The endotherm in (b) at approximately 540 ''C corresponds to the melting of the EuI? residue, remaining after the decomposition of (C~H9NH~)~EuI~. Each scan was performed in flowing argon with a ramp rate of 2'C min '. [Reprinted from D. B. Mitzi and K. Ihg, C'hn. Mater:, 9, 2900 (1997). Copyright K) 1097 American Chemical Society.]

72. C. Solution chemistry 1.Simple Organic Cations
Simultaneous TGA and DTA scans for (a) CjHyNfI3)2GeI4, (h) (C4HoNH3)2-SnIj. and © (CjHsNHj)2PbIj. Each scan was performed in flowing argon with a ramp rate of 2'C min '

73. 2. Less Stable Metal Oxidation States
more stable divalent transition metal cations, compounds involving Fez+ (18) and Cr” (123) need to be synthesized in an inert (oxygen-free) atmosphere to avoid oxidation to Fe’+ and Cs+
Group 14 (IVA) metal (Pb2+, Sn2+, or Ge”) compounds, the divalent state becomes less stable moving up the column of the periodic table from Pb” to Ge2
order to prevent the hydriodic acid from oxidizing, crystal growth is carried out in an inert atmosphere.
3. More Complex Organic Cations
4. Gel Techniques and Layered Growth
5. Multilayer Structures
6. Cyanamide Chemistry and the (1 10) Oriented Compou