Correlating miscibility, mechanical parameters, and stability of ternary polymer blends for high-performance solar cells

Abstract

With the rapid emergence of new polymer acceptors, the photovoltaic performance of all-polymer solar cells (all-PSCs) has been greatly improved. However, how to rationally design multicomponent active layers for thermally and mechanically stable all-PSCs remains challenging due to a lack of guiding principles for modulating morphology. In this work, we correlate miscibility between the third components and the host polymer donor/acceptor with the aggregated structure and mechanical behaviors in ternary all-PSCs. The new correlations of miscibility–morphology–thermal stability and miscibility–morphology–mechanical parameters in ternary blend films are established. Based on material-specific interaction parameters and microstructural features, we present the first classification of four types of ternary blends (including an over 18% efficiency system) and ascertain the corresponding models for predicting mechanical parameters. The miscibility-based mechanical models also exhibit good quantitative agreement with experimental data from two newly reported ternary systems. As such, the established miscibility–function relationships are helpful to predict the mechanical properties and stability of organic photovoltaic devices based on multicomponent systems.