Energy level matching between transparent conducting electrodes and the electronic transport layer to enhance performance of all-inorganic CsPbBr3 solar cells

Perovskite solar cells (PSCs) have become a promising research direction in photovoltaic field, where the evolution of the transparent conductive oxides (TCOs) electrodes, a vital part of photovoltaic devices, has played a distinctive role in their development. To date, the indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) have been widely used as TCOs in state-of-the-art PSCs. However, the energy level matching between the TCO electrodes and the electron transport layers (ETLs) are usually ignored. Herein, Ta doped SnO 2 (TTO) films have been prepared by the high target utilisation sputtering (HiTUS) technology, which exhibited the lowest resistivity of 7.8 × 10 −4  Ω cm and the average transmittance in the visible light region over 85%. A maximum power conversion efficiency (PCE) with 6.48% was achieved when the TTO films as the bottom electrodes in CsPbBr 3 PSCs, higher than that of PSCs based on FTO (5.36%). Especially, the open-circuit voltage ( V oc ), short-circuit current ( J sc ) and fill factor ( FF ) were all enhanced, which were attributed to the suitable energy level matching between the TCOs and ETLs layers and their low interface roughness. This work demonstrates the band structure of the TCOs and ETL layers and the roughness of TCOs have more important influence on the PCE of PSCs under the similar optical and electrical properties of TCOs condition.