Band offset optimization in MAGeI3 based perovskite solar cells

The study focuses on a complete modelling of perovskite solar cell (PSC) employing methyl ammonium germanium iodide (MAGeI₃) as light absorbing material via optimizing device’s conduction band offset (CBO) and valence band offset (VBO), which helps in identifying the suitable transport materials that can be employed for extracting the best photovoltaic parameters for solar cell. The device architecture FTO/TiO₂/MAGeI₃/CuO/Pd has been considered for the study, which after the input parameter optimization provides a power conversion efficiency (PCE) of 12.33 %. An optimization of the CBO of the device configuration results in a PCE of 13.57 %, indicating that the chosen ETL, TiO₂ is suitable for the device configuration. An alternate ETL, IGZO with the required electron affinity of 4.18 eV, when tested for the device shows a PCE of 12.39 %. The VBO optimization of the device configuration FTO/TiO₂/MAGeI₃/CuO/Pd suggests the inclusion of CZTS as the HTL and further input parameter optimization of the device provides PCE of 16.59 %. The VBO optimization of FTO/IGZO/MAGeI₃/CuO/Pd suggests for the inclusion of CZTS as the HTL, and provides an excellent PCE of 14.57 %. Hence, the CBO and VBO optimized device configuration, FTO/IGZO/MAGeI₃/CZTS/Pd is again optimized by changing the parameters of perovskite and transport layers and a PCE of 20.54 % is achieved. It is further analysed considering diverse back contact metal and optimum PCE of 20.57 % is attained, with Se as the back metal contact. An estimation of the QE of FTO/IGZO/MAGeI₃/CZTS/Se configuration indicates efficient charge generation and collection in visible and NIR wavelength regimes.