High performance ternary organic solar cells due to favored interfacial connection by a non-fullerene electron acceptor with cross-like molecular geometry

The non-fullerene electron acceptor, TPB, exhibits a unique cross-like molecular geometry which helps it to stay preferentially at the interfaces between PTB7-Th and PC₇₁BM, when it is used as the third component in ternary OPV cells. The four PDI units connected to TPB's core provide multiple contact points between PTB7-Th and PC₇₁BM phases, thus facilitating interfacial charge extraction and improving the overall PCE to 10.6% from 9.8% after 10% TPB was added as the third component. This paper describes detailed experimental results and a model to explain these observations.