Herein, we present an efficient approach for screening the intrinsic photostability of organic absorber materials used in photovoltaic applications. Using a series of structurally related conjugated polymers and a set of complementary techniques, we established important “material structure–photostability” relationships. In particular, we have revealed that the introduction of alkoxy, thioalkyl, and fluorine substituents adversely affects the material photostability. Further systematic screening of different types of materials using the developed techniques should yield a set of guidelines for designing more stable absorber materials for organic solar cells.