PCBM Constructing Heterojunction for Efficient CsPbI₃ Perovskite Quantum Dot Solar Cells

CsPbI₃ perovskite quantum dots (PQDs) have emerged as promising photovoltaic materials for third-generation solar cells, owing to their superior optoelectronic properties. Nevertheless, the performance of CsPbI₃ PQD solar cells is primarily hindered by low carrier extraction efficiency, largely due to the insulative ligands. In this study, we introduced a semiconductor molecule, [6,6]-phenyl C₆₁ butyric acid methyl ester (PCBM), onto the surfaces of CsPbI₃ PQDs as surface ligands to enhance photogenerated charge extraction. The results indicate that PCBM accelerates carrier separation in CsPbI₃ PQDs by forming a type II heterojunction, and also modulates the energy level of CsPbI₃ PQDs by altering surface dipole moments. Additionally, we established an energy-level gradient alignment in the PCBM/CsPbI₃ PQD heterojunction absorber layer, which was found to effectively promote carrier extraction and reduce carrier recombination loss in PQD solar cells. Ultimately, the PQD solar cells incorporating this novel structure achieved a power conversion efficiency of 14.23%, a significant improvement compared to 12.69% achieved by solar cells with a traditional structure, thus demonstrating the strong potential of this approach for high-performance PQD solar cells.