Solution-Processed Co<sub>3</sub>O<sub>4</sub>-Based Hole Transport Layer for Nonfullerene Organic Solar Cells
Hemraj Dahiya, Rakesh Suthar, Manish Kumar Singh, Rahul Singhal, Supravat Karak, Ganesh D. Sharma
Abstract
The imperative for achieving commercial success in organic solar cells (OSCs) lies in their efficient and stable operation within open-air environments, which enables large-scale production while concurrently reducing manufacturing costs. Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is usually used as a hole transporting material in the conventional configuration of OSCs; however, the observations reveal inferior stability due to its acidic and hygroscopic tendency. Therefore, introducing a hole transport layer (HTL) for replacing PEDOT:PSS is essential for OSCs. This work highlights both these issues; a simple and low-cost solution-processed Co 3 O 4 HTL was developed for nonfullerene-based OSCs in open-air conditions. The cobalt(II) acetate tetrahydrate (CATH) and adipic acid precursors were used to synthesize the Co 3 O 4 HTL under ambient conditions through one-shot mixing. To control the electronic properties of the Co 3 O 4 HTL thin film, thermal annealing (TA) and UV–ozone (UVO) post-treatment were employed. OSCs with the Co 3 O 4 HTL afford an excellent power conversion efficiency of 14.13% for the PM6:Y6 absorber layer, which is much higher than that of the control PEDOT:PSS (12.62%) and CATH (13.01%) counterpart. Interestingly, the derived Co 3 O 4 HTL-based OSC exhibited higher stability with the continuous illumination of AM1.5G lights under ambient conditions. In conclusion, this work emphasizes the pivotal role of solution-processed Co 3 O 4 -based HTLs in advancing the efficiency and stability of nonfullerene OSCs, contributing to the advancement toward efficient and sustainable photovoltaic technologies.