Hole-Conductor-Free, Metal-Electrode-Free TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on a Low-Temperature Carbon Electrode

Abstract

Low cost, high efficiency, and stability are straightforward research challenges in the development of organic–inorganic perovskite solar cells. Organolead halide is unstable at high temperatures or in some solvents. The direct preparation of a carbon layer on top becomes difficult. In this study, we successfully prepared full solution-processed low-cost TiO₂/CH₃NH₃PbI₃ heterojunction (HJ) solar cells based on a low-temperature carbon electrode. Power conversion efficiency of mesoporous (M-)TiO₂/CH₃NH₃PbI₃/C HJ solar cells based on a low-temperature-processed carbon electrode achieved 9%. The devices of M-TiO₂/CH₃NH₃PbI₃/C HJ solar cells without encapsulation exhibited advantageous stability (over 2000 h) in air in the dark. The ability to process low-cost carbon electrodes at low temperature on top of the CH₃NH₃PbI₃ layer without destroying its structure reduces the cost and simplifies the fabrication process of perovskite HJ solar cells. This ability also provides higher flexibility to choose and optimize the device, as well as investigate the underlying active layers.