Enhanced charge transport of wide-bandgap perovskite solar cells enabled by crown ether-mediated crystal modulation

Further improving the performance of wide-bandgap perovskite solar cells has attracted significant attention due to its crucial role in further lifting the power conversion efficiency (PCE) of perovskite-based tandem solar cells. The majority of the efforts have focused on reducing the loss of open-circuit voltage (V), while little attention has been paid to improving the fill factor (FF). Herein, we employ a crown ether to manipulate the crystallization process of wide-bandgap perovskites. The strong affinity of crown ether with the metal cations suppresses the fast precipitation of cesium salts and delays the crystallization process during the deposition of the perovskite, leading to large grains and elimination of lateral grain boundaries. Moreover, the perovskite film treated with the crown ether exhibits a pronounced orientation of (110), leading to high conductivity and mobility. The improved charge transport properties within the perovskite significantly increase the FF of the as-prepared perovskite solar cell by an absolute value of 3%. In combination with the passivation of uncoordinated Pb defects, the champion wide-bandgap (1.68 eV) solar cell with an n-i-p architecture shows a high FF of 83%, a V of 1.21 V, and a PCE of 20.6%. Meanwhile, the long-term stability of the devices is enhanced, with the unencapsulated devices retaining 99.6% of their initial PCE after 1080 hours of storage in air. This work presents a new strategy to further improve the performance of wide-bandgap perovskites and perovskite-based tandem devices.