Composition Manipulation Boosts the Efficiency of Carbon-based CsPbI3Perovskite Solar Cells to beyond 14%

The inorganic CsPbI3perovskite obtained from dimethylammonium iodide (DMAI)-related strategies have greatly promoted the development of CsPbI3perovskite solar cells (PSCs). However, deeper understandings are urgently needed to further enhance device performance. Herein, the crystallization processes of DMAI-based strategy are systematically studied and some new understandings are proposed. During annealing, β-phase-like CsPbI3is first formed and then gradually transits to γ-phase-like structure. DMA ions tend more to form DMAPbI3in the system, implying the amount of alloyed DMA ions in CsPbI3would be very limited. In addition, the pre-generated Cs4PbI6plays an important role in stabilizing CsPbI3perovskite phase at low temperature. These findings help us to finely manipulate film composition, and the quality of CsPbI3film is substantially improved after simultaneously suppressing the formation of δ-CsPbI3, minimizing DMAPbI3residual and generating PbI2passivator. More promisingly, the carbon-based CsPbI3PSCs without hole transporter achieve a record efficiency of 14.6%.