On the Glass Transition of Polymer Semiconductors and Its Impact on Polymer Solar Cell Stability

Abstract

The glass transition temperature is a critical processing parameter that governs the kinetics of molecular organization of polymer semiconductors during solidification. Yet, little attention is paid to the resulting structure-processing-property relationships that lead to optimal optoelectronic performance, which is usually obtained with nonequilibrium nanostructures. This review elucidates the interplay of molecular design and glass transition phenomena that are common to the most well-studied families of conjugated polymers, including polyfluorenes, polythiophenes, and poly(p-phenylenevinylene)s. The influence of key structural factors—known from classical polymer science—such as molecular weight, chain rigidity, side-chain architecture, and intermolecular π–π interactions, is explored in order to provide rationales that can guide the synthesis of new polymer semiconductors with tailored glass transition temperatures. Moreover, the discussion is anchored in an overview of the main measurement techniques...