Performance Enhancement of Hole Transport Layer-Free Carbon-Based CsPbIBr2 Solar Cells through the Application of Perovskite Quantum Dots

CsPbIBr2, with its suitable bandgap, shows great potential as the top cell in tandem solar cells. Nonetheless, its further development is hindered by a high defect density, severe carrier recombination, and poor stability. In this study, CsPbI1.5Br1.5 quantum dots were utilized as an additive in the ethyl acetate anti-solvent, while a layer of CsPbBr3 QDs was introduced between the ETL and the CsPbIBr2 light-harvester film. The combined effect of these two QDs enhanced the nucleation, crystallization, and growth of CsPbIBr2 perovskite, yielding high-quality films characterized by an enlarged crystal size, reduced grain boundaries, and smooth surfaces. And a wider absorption range and better energy band alignment were achieved owing to the nano-size effect of QDs. These improvements led to a decreased defect density and the suppression of non-radiative recombination. Additionally, the presence of long-chain organic molecules in the QD solution promoted the formation of a hydrophobic surface, significantly enhancing the long-term stability of CsPbIBr2 PSCs. Consequently, the devices achieved a PCE of 9.20% and maintained an initial efficiency of 85% after 60 days of storage in air. Thus, this strategy proves to be an effective approach for the preparation of efficient and stable CsPbIBr2 PSCs.