Stability and charge transport analysis of high-performance PM6:Y7 nonfullerene organic solar cells using the metal–insulator–metal model

Abstract

Non-fullerene acceptors are promising materials for organic solar cells because of their flexibility and low cost; however, their long-term stability remains a critical challenge. In this study, we investigate the degradation mechanisms of conventionally structured solar cells (ITO/PEDOT: PSS/PM6/Y7/PDINO/Ag) under different environmental conditions: nitrogen preservation, encapsulation, and air exposure. Using the metal-insulator-metal (MIM) model, we simulate the current-voltage characteristics and extract key parameters to understand the physical mechanisms governing device degradation. The results show that air exposure primarily affects the anode interface, reducing the interfacial dipole energy and shifting the Fermi-level alignment of PEDOT: PSS, which is crucial for efficient hole extraction. This process leads to a deterioration in the hole transport properties over time, significantly affecting device performance. In contrast, the cathodic interface remains stable, suggesting that degradation is largely driven by changes in the hole transport layer. These findings provide critical insights into the interfacial degradation mechanisms of the NFA-based solar cells. Understanding these effects will aid in the development of strategies to enhance the stability and efficiency of organic photovoltaic devices for long-term operation.