From particles to films: production of Cs2AgBiBr6-based perovskite solar cells and enhancement of cell performance via ionic liquid utilization at the TiO2/perovskite interface

Abstract

Herein, Cs₂AgBiBr₆ particles produced by the traditional super-saturation precipitation method were used as precursors to create Cs₂AgBiBr₆ films by the gas-quenching process under ambient atmospheric conditions. These films were utilized as a light-absorbing layer in hole-transporting free perovskite solar cells (PSCs) with carbon electrodes. Furthermore, the incorporation of the 1-butyl-3-methylimidazole hexafluorophosphate (BMIMPF6) ionic liquid (IL) at the metal oxide electron transporting layer/perovskite interface resulted in enhanced crystallinity of the perovskite, forming large perovskite grains of up to 800 nm. However, it was discovered that establishing the optimal concentration for passivating surface defects takes precedence over encouraging the growth of larger perovskite grains. The utilization of the optimized BMIMPF6 concentration led to a remarkable increase in the power conversion efficiency (PCE) of the cell, with a boost of over 31% to reach 1.67%, when compared to the cell produced without the inclusion of the IL. Our findings underscore that the passivation of surface defects between the TiO₂ and perovskite layers holds more importance for enhancing the PCE of Cs₂AgBiBr₆-based perovskite solar cells than focusing solely on the perovskite morphology.