Band Alignment and Performance Optimization in Organic Solar Cells with Quantum Dot Hole-Transport Layers

Organic solar cells provide fascinating solutions for sustainable energy conversion. However, inefficient hole transport layers limit their performance by restricting charge extraction and facilitating interfacial charge recombination. This study provides a comprehensive simulation-based performance analysis of organic photovoltaic cells using PbS, PbSe, and PbS-TBAI quantum dots as alternative HTLs in the AZO/PM6:Y6/QD solar cell architecture. We used numerical simulations to carefully evaluate the effect of QD type, thickness, doping concentration, and defect density on photovoltaic parameters. PbS QDs-based devices surpass PbSe-based (21.23%) and PbS (QD)-TBAI-based devices (19.71%) due to their greater intrinsic material proper-ties, superior interfacial chemistry, better tolerance to defects and thermal stress, and perfect band alignment with the PM6:Y6 active layer, resulting in a notable power conversion efficiency of 22.19%. The PbS-based devices displayed acceptable thermal stability and trap tolerance, keeping 92.5% of their original PCE even at high defect densities (~10²⁰ cm^-3). A thorough band alignment study demonstrated that flat-band conditions at the PbS/PM6:Y6 interface reduce non-radiative recombination, but the insulating TBAI ligand layer in PbS-TBAI devices creates tunnelling barriers and Fer-mi-level pinning. This study presents essential design concepts for choosing and de-veloping QD-based HTLs, establishing PbS QDs as the best choice for high-efficiency, stable, solution-processed OPV cells, with important implications for next-generation photovoltaic technologies.