Utilizing magnetic field to study the impact of intramolecular charge transfers on the open-circuit voltage of organic solar cells

Abstract

Improving the power conversion efficiency of organic solar cells is the essential theme for future application. Open-circuit voltage (Voc) loss of photovoltaic devices is a serious problem preventing performance enhancement. Here, in block copolymer based photovoltaic devices, we study intramolecular charge transfer (intra-CT) states dependent Voc loss (Vloss) through involving multi-beam excitation together with the magnetic field. Along with generating substantial intra-CT states in organic solar cells, the performance of Voc is improved. Magnetic field could increase triplet intra-CT states in copolymer to further decrease Vloss. Furthermore, intra-CTs could result in larger charge dissociation to induce photoluminescence quenching. Overall, we observe that intra-CT states in block copolymer play an important role for the Voc performance in organic solar cells.