In-Operando Study of the Effects of Solvent Additives on the Stability of Organic Solar Cells Based on PTB7-Th:PC71BM

Degradation of organic solar cells is among the fundamental problems that hinder their successful breakthrough. We probe in-operando the degradation behavior of organic solar cells based on the high-efficiency low-bandgap benzodithiophene copolymer PTB7-Th and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The influence of the solvent additives 1,8-diiodooctane and o-chlorobenzaldehyde on the degradation mechanism is studied with in situ grazing incidence small-angle X-ray scattering during operation. Changes in the IV characteristics are correlated for the first time in situ with changes in the morphology showing that the use of a solvent additive causes a change in device degradation.