Presentation on theme: "Title Interface recombination & emission applied to explain photosynthetic mechanisms for (e-, h+) charges separation Marco Sacilotti a,c, Denis Chaumont."— Presentation transcript:
Title Interface recombination & emission applied to explain photosynthetic mechanisms for (e-, h+) charges separation Marco Sacilotti a,c, Denis Chaumont c, Claudia Brainer Mota a, Thiago Vasconcelos b, Frederico Dias Nunes b, Marcelo Francisco Pompelli d, Sergio Luiz Morelhao e, Anderson S. L. Gomes a a Department of Physics, Universidade Federal de Pernambuco, Recife, Brazil. b Departament of Eletronics and Systems, Universidade Federal de Pernambuco, Recife, Brazil. c Nanoform Group ICB & UFR Sc. Techn. FR 2604 – Universit é de Bourgogne, 9 avenue A. Savary, Dijon, France. d Plant Physiology Laboratory, Universidade Federal de Pernambuco, Department of Botany, CCB, Recife, Brazil. e Physics Department, Universidade de Sao Paulo - Cidade Universitaria Sao Paulo Brazil World Journal of Nano Science and Engineering http://www.scirp.org/journal/wjnse Paper ID: 4400054 Support Information: SI-1 Energy staggered interface: electrical charge separation mechanism. 1
Figure SI-1-1, representing the energy staggered interface: electrical charge separation mechanism. How does the energy band bending arrive at the energetic interface? The flow of charges from one material to the nearby material creates an electronic no-equilibrium on both materials, near the interface. This electronic non-equilibrium creates potential variation. It creates the necessary electric field to separate charges: e- from h+. CB VB CB Material A Material B interface - + Energy band bending. Electric field = - grad V Force = E x charge energy = V x charge Note that quasi-Fermi level E FB should go up, CB & VB go down for B. E FB Note that quasi-Fermi level E FA should go down, CB & VB go up for A. E FA 2
BC BV BC CathodeCathode Material A AnodeAnode Material B interface Figure SI-1-2, representing the energy staggered interface. It represents the charge separation mechanism in a picturial slow motion maner. Excitation of such an energetic structure with only 4 photons. + - 2hv - + + - + ---- - +++ + - + hvihvi --- +++ - + +++ --- - + - + hvihvi + - + - + - + - + - + - hvihvi Energy balance:4 hv photons as excitation 3 hv i photons emission at interface 1 (e -, h + ) separated ( 25% efficiency) hv i is related to the spent energy to separate (e -, h + ). Note: photosynthesis is about 5% final efficiency. 3
BC BV BC CathodeCathode Material A AnodeAnode Material B interface hvihvi Figure SI-1- 3, representing the energy staggered interface: charge separation mechanism applied to photosynthetic first step processes. Note the hudge electric field crossing the interface for the AlInAs/InP system (see text). For organic molecules, this electric field should be much higher since the excitonic attraction is much higher than for inorganic materials. - + - + + + - - water O2O2 CO 2 + H2O sucrose Interface electric field crossing the interface E band-bending 10 5 V/cm 4
Why is the interface emission peak so large? See it in the nexts slides… 5
Figure SI-1-4, representing the interface physical parts linked to the interface emission peak. All the terms of the equation below should change with the excitation intensity. Mainly Q e + Q h should change more than the others terms. This explain why the interface PL & EL emission peaks are so large. Note: no quantum mechanics selection rules, for e- & h+ recombination at the interface 6 interface hv i <-- electrons holes --> = S + Q e + Q h - E x Q e Q h S _ + E x = interaction Material A Material B h absorption is possible Energy levels to be filled up with h+, upon light excitation. Quasi-triangular shape quantum well for e-.
Figure SI-1-5, representing the interface physical parts linked to the interface recombination/emission peak. The interface recombination and emission depends on the e- & h+ wavefunctions interface overlap. The 1 to 2 nm wavefunction penetration is for the AlInAs/InP system (see text). No quantum mechanics selection rules for recombination; because e- & h+ are seated on different materials. 7 interface hv <-- electrons holes --> emission & absorption Material A Material B Permanent e- population inversion (µ e- > µ h+ ) + ~1 nm - ~ 2 nm Is there any meaning to talk about lifetime measurements for all these hazardous energy levels (e-, h+) recombination? S h+ wavefunction e- wavefunction