1. Rui Wang, Jintao Wang, Shaun Tan, Yu Duan, Zhao-Kui Wang, Yang Yang
Opportunities and Challenges of Lead-Free Perovskite Optoelectronic Devices 
Rui Wang, Jintao Wang, Shaun Tan, Yu Duan, Zhao-Kui Wang, Yang Yang 
Trends in Chemistry 
DOI: /j.trechm
Copyright © Terms and Conditions

2. Figure 1 An Energy Diagram of Common Lead-Free Perovskites.
The diagram shows electron-transporting layers (ETLs) and hole-transporting layers (HTLs). Energy values shown are in electron volts.
Trends in Chemistry DOI: ( /j.trechm )
Copyright © Terms and Conditions

3. Figure 2 Structures of Lead-Free Perovskites.
(A) 3D crystal structure of CH3NH3SnI3-xBrx [24]. (B) 2D layered structure of Cs3Sb2I9 [23]. (C) Local structure of the Bi2I93- anion (left); cation and anion positions in the unit cell (right) [12]. (D) The crystal structure of Cs2AgBiBr6 [28].
Trends in Chemistry DOI: ( /j.trechm )
Copyright © Terms and Conditions

4. Figure 3
Fabrication Processes of the Lead-Free Perovskite Solar Cells (PSCs).
(A) Summary of the spin-coating and evaporation process. (B) Low-pressure-assisted fabrication process [32]. (C) Schematic of the vapor-assisted solution process (VASP) and low-temperature VASP (LT-VASP) fabrication processes [36].
Trends in Chemistry DOI: ( /j.trechm )
Copyright © Terms and Conditions

5. Figure 4
Stability of Lead-Free Perovskite Solar Cells under Different Environmental Conditions.
These include encapsulated (E), unencapsulated (UE), ambient conditions (air), glove box (N2), and heat.
Trends in Chemistry DOI: ( /j.trechm )
Copyright © Terms and Conditions

6. Figure I Lead Toxicity and Associated Symptoms.
Trends in Chemistry DOI: ( /j.trechm )
Copyright © Terms and Conditions