17.3% efficiency CsPbI2Br solar cells by integrating a Near-infrared absorbed organic Bulk-heterojunction layer

All-inorganic perovskite solar cells (PSCs) have gained extensive attention owing to the excellent intrinsic thermal stability, but their power conversion efficiencies (PCEs) still lag behind those of organic–inorganic hybrid PSCs due to their relatively wide bandgap. To extend the absorption of CsPbI2Br based all-inorganic PSCs, in this work, a low bandgap organic active layer of PM6:Y6 is integrated on the top of CsPbI2Br layer. Compared with CsPbI2Br PSCs using PM6 as hole transport layer, the integrated solar cells (ISCs) obtained an extended photo-response range to 950 nm and improved short-circuit current density (JSC) from 14.25 to 15.44 mA cm−2, as well as promoted PCE from 15.31% to 17.33%. Furthermore, the photoluminescence (PL), time-resolved-photoluminescence (TRPL), photoinduced transient absorption spectroscopy (TAS), transient photocurrent (TPC), and transient photovoltage (TPV) results demonstrate the effective carriers’ bidirectional transport and suppressed carriers’ recombination at CsPbI2Br/PM6:Y6 interface, which is the basis for ISCs to obtain high efficiency. Our findings demonstrate that ISC is a promising strategy to extend the photo-response range and improve the performance of CsPbI2Br based PSCs, and give a deeper understanding of carrier transfer in ISCs.