p-Toluenesulfonic Acid Modified Two-Dimensional ZrSe₂ as a Hole Transport Layer for High-Performance Organic Solar Cells

Two-dimensional (2D) materials have attracted attention due to their excellent optoelectronic properties, but their applications are limited by their defects and vacancies. Surface modification is an effective method to restore their performance. Here, ZrSe 2 is modified with conductive polymer p -toluenesulfonic acid (PTSA). It is found that PTSA can obtain electrons of ZrSe 2 through the combination of −SO 3 H and ZrSe 2, thus forming interfacial dipoles, which improve the work function of ZrSe 2 . In addition, −OH in PTSA can effectively fill the Se vacancy in ZrSe 2 to form P-type doping, thereby improving its conductivity. ZrSe 2 modified by the PTSA material is first used as a hole transport layer (HTL) in organic solar cells (OSCs). The efficiency of OSCs based on the PBDB-T:ITIC and PM6:L8-BO binary active layer with ZrSe 2:PTSA as the novel HTL reaches 10.66 and 18.14%, which are obviously higher than the efficiency of OSCs with pure ZrSe 2 as the HTL (8.48 and 15.64%). More interestingly, the stability of the device with ZrSe 2:PTSA as HTL is significantly better than that of PEDOT:PSS. This study shows that the modification of the organic material can effectively improve the photoelectric performance of ZrSe 2 and explores the physical mechanism of the interaction between the organic modifier and 2D materials.