Enhancing the optical, morphological and electronic properties of the solution-processed CsPbIBr2 films by Li doping for efficient carbon-based perovskite solar cells

CsPbIBr 2 perovskite exhibits the most balanced bandgap and durability features among all the inorganic perovskites, showing great potential in the photoelectric field. Nevertheless, the poor film quality of the traditionally spin-coated CsPbIBr 2 restricts the further improvement of the device performance. Here, we develop a novel lithium (Li) doping strategy to promote the optical, morphological and electronic properties of the solution-processed CsPbIBr 2 perovskites. Upon incorporating Li + ions into CsPbIBr 2 lattice, highly crystallized and well-oriented CsPbIBr 2 crystals are obtained. The as-prepared Li-doped CsPbIBr 2 exhibits a higher film coverage over the substrate with larger grains and less grain boundaries compared to the none-doped counterparts. The trap-state densities in the CsPbIBr 2 film are also effectively alleviated while the carrier lifetimes are elongated by Li doping, contributing to a lower energy loss and a higher charge collection efficiency. The optimized Li-doped perovskite solar cells (PSCs) demonstrate an excellent champion power conversion efficiency (PCE) of 9.25%, much higher than that of the none-doped devices (7.41%). Furthermore, the unencapsulated devices present a superior air and thermal stability under the protection of the hydrophobic CuPc layer and carbon electrode. Our work provides a new opportunity to fabricate cost-effective and highly efficient CsPbIBr 2 PSCs in a facile way.