Physics

Nanotechnology

Energy conversion efficiency

Polythiophene

Engineering

Perovskite (structure)

Conductive polymer

Voltage

Composite material

Halide

Inorganic chemistry

Trihalide

Chemistry

Materials science

Condensed matter physics

Annealing (glass)

Acceptor

Layer (electronics)

Quantum mechanics

Passivation

Chemical engineering

Optoelectronics

Polymer

Open-circuit voltage

Advanced Materials

Cesium‐based trihalide perovskites have been demonstrated as promising light absorbers for photovoltaic applications due to their superb composition stability. However, the large energy losses ( E loss ) observed in inorganic perovskite solar cells has become a major hindrance impairing the ultimate efficiency. Here, an effective and reproducible method of modifying the interface between a CsPbI 2 Br absorber and polythiophene hole‐acceptor to minimize the E loss is reported. It is demonstrated that polythiophene, deposited on the top of CsPbI 2 Br, can significantly reduce electron‐hole recombination within the perovskite, which is due to the electronic passivation of surface defect states. In addition, the interfacial properties are improved by a simple annealing process, leading to significantly reduced energy disorder in polythiophene and enhanced hole‐injection into the hole‐acceptor. Consequently, one of the highest power conversion efficiency (PCE) of 12.02% from a reverse scan in inorganic mixed‐halide perovskite solar cells is obtained. Modifying the perovskite films with annealing polythiophene enables an open‐circuit voltage ( V OC ) of up to 1.32 V and E loss of down to 0.5 eV, which both are the optimal values reported among cesium‐lead mixed‐halide perovskite solar cells to date. This method provides a new route to further improve the efficiency of perovskite solar cells by minimizing the E loss .

Polymer‐Passivated Inorganic Cesium Lead Mixed‐Halide Perovskites for Stable and Efficient Solar Cells with High Open‐Circuit Voltage over 1.3 V