PCBM\nConstructing Heterojunction for Efficient CsPbI<sub>3</sub> Perovskite\nQuantum Dot Solar Cells

CsPbI<sub>3</sub> perovskite quantum dots (PQDs) have emerged as\npromising photovoltaic materials for third-generation solar cells,\nowing to their superior optoelectronic properties. Nevertheless, the\nperformance of CsPbI<sub>3</sub> PQD solar cells is primarily hindered\nby low carrier extraction efficiency, largely due to the insulative\nligands. In this study, we introduced a semiconductor molecule, [6,6]-phenyl\nC<sub>61</sub> butyric acid methyl ester (PCBM), onto the surfaces\nof CsPbI<sub>3</sub> PQDs as surface ligands to enhance photogenerated\ncharge extraction. The results indicate that PCBM accelerates carrier\nseparation in CsPbI<sub>3</sub> PQDs by forming a type II heterojunction,\nand also modulates the energy level of CsPbI<sub>3</sub> PQDs by altering\nsurface dipole moments. Additionally, we established an energy-level\ngradient alignment in the PCBM/CsPbI<sub>3</sub> PQD heterojunction\nabsorber layer, which was found to effectively promote carrier extraction\nand reduce carrier recombination loss in PQD solar cells. Ultimately,\nthe PQD solar cells incorporating this novel structure achieved a\npower conversion efficiency of 14.23%, a significant improvement compared\nto 12.69% achieved by solar cells with a traditional structure, thus\ndemonstrating the strong potential of this approach for high-performance\nPQD solar cells.