Molecular engineering of hole-selective layer for high band gap perovskites for highly efficient and stable perovskite-silicon tandem solar cells

In this work, a novel carbazole-based SAM (Ph-2PACz) was developed for facilitating efficient hole extraction and suppressing carrier recombination in high-band-gap (1.67 eV) perovskites for single-junction and tandem-cell demonstrations. The champion 21.3% efficient 1.67 eV cell produced a high fill factor (FF) of 82.6% and an open-circuit voltage (VOC) of 1.26 V, representing low band-gap-voltage offset at 0.41 V. When Ph-2PACz was applied to the top perovskite cell for a monolithic perovskite-Si tandem, a PCE of 28.9% (on 1 cm2) and a VOC of 1.91 V were obtained. When encapsulated, a tandem cell demonstrated excellent stability under continuous 1 sun illumination (680 h) and damp heat (280 h at 85°C + 85% relative humidity) and passed the International Electrotechnical Commission (IEC) 61215 thermal cycling (200 cycles between −40°C and 85°C) test, retaining 98.8% of the initial PCE.