Treating CsPbI3 Perovskite with Pyrrolidinium Iodide to Improve the Performance of Perovskite Solar Cells

Abstract

All-inorganic CsPbI3 perovskite has attracted wide attention due to its desirable optical bandgap (Eg: ∼1.7 eV) as well as high chemical stability. Nevertheless, the photovoltaic performance of CsPbI3 perovskite solar cells (PSCs) was limited by severe nonradiative charge recombination due to high defect density at the grain boundary and surface of perovskite films. To address this issue, a pyrrolidinium iodide (PyI) molecule was introduced to modify the surface and grain boundary of CsPbI3 perovskite films to passivate defects, which improves the quality of CsPbI3 perovskite films as well as induces the generation of a quasi-2D Py2CsPb2I7 capping layer between perovskite layer and hole transport layer. Such quasi-2D Py2CsPb2I7 capping layer optimizes interface contact between CsPbI3 perovskite layer and hole transport layer and blocks the electron transfer from CsPbI3 perovskite photoactive layer to the hole transport layer. As a result, the performance of CsPbI3 PSCs is well improved to 17.87% for power conversion efficiency (PCE) with an ultra-high fill factor (FF) of 0.84. In addition, the PyI molecule modified CsPbI3 perovskite devices exhibit excellent stability, which remains its initial PCE almost unchanged after aging for 35 days under the dry air atmosphere (temperature: 20°C–30°C, control relative humidity (RH):