Low-temperature preparation achieving 10.95%-efficiency of hole-free and carbon-based all-inorganic CsPbI3 perovskite solar cells

Abstract In this paper, hole-free, carbon-based all-inorganic CsPbI3 perovskite solar cells (PSCs) with the structure of F-doped SnO2 (FTO)/ZnO/CsPbI3/C are fabricated at a low temperature for the first time. Excess CsBr is added into CsPbI3 precursor solution to obtain stable black phase CsPbI3 at a low temperature (120 °C). ZnO is prepared by a spin-coating method at 120 °C. And then the C electrode is prepared by a doctor-blade method at 120 °C. The effect of different layers of ZnO on the performance of solar cells is investigated. The champion power conversion efficiency (PCE) of the solar cell based on 3 layers of ZnO is 10.95%, with a short-circuit current (JSC) of 17.66 mA/cm2, an open-circuit voltage (VOC) of 0.91 V and a fill factor (FF) of 68%, which is the best performance for hole-free, carbon-based all-inorganic CsPbI3 PSCs fabricated at a low temperature, compared with the other reported results. The encapsulated device remained 91% of the initial PCE after being stored in a glove box for 5 months. For further application in flexible solar cells, the solar cells with the structure of PET/Sn-doped In2O3 (ITO)/ZnO/CsPbI3/C are fabricated under the best parameter conditions and the PCE of 8.70% is obtained.