Enhancing the optical, morphological and electronic properties of the solution-processed CsPbIBr_2 films by Li doping for efficient carbon-based perovskite solar cells

摘要

CsPbIBr2 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 CsPbIBr2 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 CsPbIBr2 perovskites. Upon incorporating Li+ ions into CsPbIBr2 lattice, highly crystallized and well-oriented CsPbIBr2 crystals are obtained. The as-prepared Li-doped CsPbIBr2 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 CsPbIBr2 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 CsPbIBr2 PSCs in a facile way.