Pb-free perovskite solar cells are investigated to eliminate the toxic Pb. However, the Pb-free perovskite solar cell with power conversion efficiency (PCE) of below 9% has been reported mainly because of low open circuit voltage (VOC). In this contribution, the theoretical analysis of the Pb-free perovskite solar cells with an inverted p-i-n planar structure, where the perovskite is FA0.75MA0.25Sn0.95Ge0.05I3 (Sn–Ge perovskite), was therefore conducted using device simulation. It is disclosed that VOC is positively affected by built-in potential across the perovskite absorber (Vbi). The Vbi is primarily governed by conduction band minimum (EC) of electron transporting layer (ETL) and/or work function of back contact (Φ_BC), where they should not be deeper (lower) than the EC (−3.67 eV) of the Sn–Ge perovskite absorber to avoid the Vbi loss for high VOC. Consequently, the ETL and BC materials in the Sn–Ge perovskite solar cells should be appropriately chosen for both suitable conduction band offset of perovskite and ETL, as well as the difference of the EC of perovskite and Φ_BC, thus developing the device structure and increasing Vbi and VOC for the improved PCE.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films