Integrated Ideal‐Bandgap Perovskite/Bulk‐Heterojunction Solar Cells with Efficiencies > 24%

Abstract Here, the authors report a highly efficient integrated ideal‐bandgap perovskite/bulk‐heterojunction solar cell (IPBSC) with an inverted architecture, featuring a near infrared (NIR) polymer DTBTI‐based bulk‐heterojunction (BHJ) layer atop guanidinium bromide (GABr)‐modified FA 0.7 MA 0.3 Pb 0.7 Sn 0.3 I 3 perovskite film as the photoactive layer. The IPBSC shows cascade‐like energy level alignment between the charge‐extractionlayer/perovskite/BHJ and efficient passivation effect of BHJ on perovskite. Thanks to the well‐matched energy level alignment and high‐quality ideal bandgap‐based perovskite film, an efficient charge transfer occurs between the charge‐extraction‐layer/perovskite/BHJ. Moreover, the NIR polymer DTBTI on the perovskite film leads to an improved NIR light response for the IPBSC. In addition, the O, S and N atoms in the DTBTI polymer yield a strong interaction with perovskite, which is conducive to reducing the defects of the perovskite and suppressing charge recombination. As a result, the solar cell achieves a power conversion efficiency (PCE) of 24.27% (certificated value at 23.4% with 0.283‐volt voltage loss), currently the recorded efficiency for both IPBSCs and Pb‐Sn alloyed PSCs, and which is over the highest efficiency of perovskite–organic tandem solar cell. Moreover, the thermal, humidity and long‐term operational stabilities of the IPBSCs are also significantly improved compared with the control PSCs.