LAUSR

Currently, two-dimensional (2D) perovskite solar cells (PSCs) with high moisture resistance have become the focus of photovoltaic field. However, their lower PCE in comparison to 3D PSCs is still urgent problems to be solved. It is vital to understand the impact of constituent ratios and ammonium salt sizes on the photovoltaic performance and humidity stability. Herein, based on the formula of (RNH3)2(MA)n-1PbnI3n+1 (n=1, 3, 5, 7, 9 and 11), we prepared a series of 2D perovskites by introducing varisized ammonium salts of ethylammonium iodide (EAI), propylammonium iodide (PAI) and butylammonium iodide (BAI). The effects of constituent ratios and varisized ammonium salts on the properties of 2D perovskites were studied. The results show that the 2D perovskite devices based on larger n and smaller ammonium salts size will exhibit more predominant performances. However, the moisture resistance of 2D perovskite devices will be higher when n is smaller and ammonium salts size is larger. Therefore, the EA2MA10Pb11I34 (n=11) 2D perovskite device displays the best photovoltaic performances with highest PCE of 16.93%, whereas BA2MA2Pb3I10 (n=3) 2D perovskite with largest contact angles of 79.8° can retain over 85% of initial PCE after 1440-h aging at 50% RH. This work indicates the PCE and stability of 2D perovskites can be conveniently and effectively adjusted by controlling the 2D constituent ratios and ammonium salt sizes, so as to obtain efficient 2D PSCs with high stability.