摘要： Organic-inorganic halide perovskite (ABX3) solar cells (PSCs) have made great progress in recent years [1]. The power conversion efficiency (PCE) has increased up to 25.2% (NREL Best Research-Cell Efficiency Chart, https://www.nrel.gov/pv/cell-efficiency.html, Accessed August 2019). However, they suffer from poor thermal stability due to the volatile A-site organic cations. All-inorganic CsPbI3–xBrx perovskite materials can tolerate temperature exceeding 400 °C, while organic–inorganic halide PSCs rapidly deteriorated at greater than 200 °C [2]. The excellent thermal stability of inorganic perovskites makes them promising materials for PSCs [3]. Their relatively low PCE is due to two reasons. One is the wide bandgap, which leads to insufficient light absorption and low Jsc. Developing tandem solar cells is an effective approach to absorb sunlight as much as possible [4]. Another is the large energy loss (Eloss), leaving much room for increasing Voc. Interface engineering can reduce the Eloss and increase the PCE. Wang et al. [5] reported a 17.06% PCE by using PTABr-treated CsPbI3 as the absorber. The post-treatment with PTABr can realize gradient Br-doping and surface passivation, leading to enhanced Voc and FF. They also modified CsPbI3 surface with choline iodine (CHI), which increased the charge-carrier lifetime and improved the energy level alignment between CsPbI3 and charge-transport layers. CHI-CsPbI3 solar cells gave a PCE of 18.4% [6]. Besides, choosing electron-transport layers (ETLs) and hole-transport layers (HTLs) with suitable energy levels is also effective for improving Voc [7]. In our previous work, we applied DPPA-modified ZnO as ETL for CsPbI2.25Br0.75 solar cells, obtaining a 15.98% PCE with an enhanced Voc [8]. Yan et al. [9] used SnO2/ZnO bilayer as ETL to get high Voc. They also used PN4N-modified SnO2 as ETL and PDCBT as HTL in CsPbI2Br solar cells, obtaining a 16.2% PCE with a 1.30 V Voc [10]. In this work, we made inorganic PSCs with a structure of ITO/SnO2/ZnO/CsPbI2.25Br0.75/HTL/MoO3/Ag (Fig. 1a). PTAA doped with polymer donor PBD2T [11] was used as HTL (D-PTAA). The deep highest occupied molecular orbital (HOMO) level of PBD2T matches HOMO of CsPbI2.25Br0.75 well. Meanwhile, PBD2T can passivate the trap states on perovskite surface and suppress interfacial charge recombination. The solar cells with D-PTAA delivered a 17.37% PCE, which is the highest efficiency for Br-doped inorganic PSCs.