Enhanced performance of inverted CsPbI3 perovskite solar cells by using carbohydrazide interface modification

Inorganic perovskite CsPbI3, with its suitable bandgap and excellent thermal stability, is a promising light-absorbing material for perovskite solar cells (PSCs). However, the detrimental defects in CsPbI3 not only act as recombination centers but also accelerate film degradation, resulting in poor power conversion efficiency (PCE) and reduced stability. Herein, carbohydrazide (CBZ) was employed as an upper surface passivator for CsPbI3 films. The amino and carbonyl functional groups of CBZ can strongly anchor to undercoordinated Pb2+ via tight coordination bonds, effectively passivating surface and grain boundary defects of CsPbI3. Additionally, CBZ modification can ameliorate film morphology, optimize interfacial energy level alignment, enhance charge extraction, and suppress non-radiative recombination. Consequently, CBZ-modified inverted PSCs yield a champion PCE of 19.76% with an outstanding fill factor (FF) of 85.26%, which is one of the highest FF reported for CsPbI3 PSCs so far. Moreover, CBZ-modified devices exhibit significantly enhanced long-term storage stability in air. This work highlights the use of molecularly engineered modifiers as a promising approach to boost the efficiency and stability of inverted PSCs, providing a valuable interface design reference.