Proceedings of nanoGe International Conference on Perovskite Solar Cells, Photonics and Optoelectronics (NIPHO19)
DOI: https://doi.org/10.29363/nanoge.nipho.2019.019
Publication date: 21st November 2018
Perovskite based solar cells (PSCs) demonstrated a remarkable increase in terms of power conversion efficiency (PCE) in few number of years exceeding 23% efficiency. Today’s state of the are perovskite solar cells containing two or more cations (MA+, FA+, Cs+ or Rb+) together with a mixture of halides (Br- and I-) showing long term stability along with high PCE values. In order to further improve the perovskites crystals quality and photovoltaic (PV) performance post deposition treatments are made. In this work we studied the effect of formammidinium iodide (FAI) and formammidinium bromide (FABr) post treatment on Cs0.2FA0.8Pb(I0.75Br0.25)3 perovskite. The FAI/FABr post treatment shows that halide exchange can occur in the solid state phase following the fabrication of the thin film perovskite. Several FAI/FABr ratios (100/0, 75/25, 50/50, 25/75, and 0/100) were studied on films complete solar cells. We found that as the FABr ratio increase the distortion in the perovskite lattice become more significant as a result of large volume differences between already exist to incorporated halides. The influence of halide exchange on a complete cells was studied through charge extraction and voltage decay measurements, which shows that the structural changes due to halide incorporation strongly affect the lifetime of the charge carriers in the perovskite layer eventually reducing the PV performance of the post treated cells compare to standard non-treated mixed cation mixed halide cells. This work demonstrates the halide exchange in the solid state phase of mixed cation mixed halide perovskite.