Numerical and experimental study of transparent electrode effect for charge transport layer-free perovskite solar cells

Despite the perovskite solar cells (PSCs) have attracted attention due to their high efficiency and lower cost compared to Si solar cells, many issues remain to be addressed for the commercialization. While the perovskite light absorbing materials is relatively inexpensive, the charge transport layers such as the hole transport layer (HTL) or electron transport layer (ETL) are usually composed of expensive organic compounds. In that sense, PSCs without the charge transport layers are developed, showing very low performance due to low charge collection efficiency. In this study, we investigate the origin of low efficiency for ETL or HTL-free PSCs, and further identify the suitable front contact (either indium tin oxide (ITO) or fluorine-doped tin oxide (FTO)) for each PSC by using numerical simulation and experimental validation. The different work functions of the front contacts significantly influence charge extraction behavior, thereby affect the charge transport layer free devices.