Thermally Stable Inorganic CsPbI₂Br Mesoscopic Metal Halide Perovskite Solar Submodules

Highly efficient and thermally stable inorganic CsPbI₂Br mesoscopic metal halide perovskite (MHP) solar cells with a poly-3-hexylthiophene (P3HT) hole transporting layer (HTL) are demonstrated by spin-washing of the P3HT HTL since the light harvesting efficiency is improved by minimizing the coabsorption of light by P3HT, and the open-circuit voltage is enhanced because of the increased valence band maximum position of the spin-washed P3HT HTL. The spin-washed CsPbI₂Br MHP solar cell exhibited 1.24 V open-circuit voltage (V_oc), 14.20 mA/cm² short-circuit current density (J_sc), 81.52% fill factor (FF), and 14.35% power conversion efficiency (PCE). The unencapsulated spin-washed CsPbI₂Br MHP solar cell went through 7.56% degradation after a 1000 h thermal stability test under 100 °C/25% relative humidity (RH) and simultaneous 1 sun light soaking conditions. In addition, the unencapsulated spin-washed CsPbI₂Br MHP solar submodule with 25 cm² of masked active area showed a 98% geometrical FF, 115.09 mA short-circuit current, 3.54 V V_oc, 71.09% FF, and 11.58% PCE while exhibiting 8.80% of degradation during a thermal stability test at 100 °C/25% RH and 1 sun light soaking for 1000 h.