Deciphering the Effects of Molecular Dipole Moments on the Photovoltaic Performance of Organic Solar Cells.

The dielectronic constant of organic semiconductor materials is directly related to its molecule dipole moment, which could be used to guide the design of high-performance organic photovoltaic materials. Here, two isomeric small molecule acceptors, ANDT-2F and CNDT-2F, were designed and synthesized by using the electron localization effect of alkoxy in different positions of naphthalene. It is found that the axisymmetric ANDT-2F exhibits a larger dipole moment, which could improve exciton dissociation and charge generation efficiencies due to the strong intramolecular charge transfer effect, resulting in the higher photovoltaic performance of devices. Moreover, PBDB-T: ANDT-2F blend film exhibits larger and more balanced hole and electron mobility as well as nanoscale phase separation due to the favorable miscibility. As a result, the optimized device based on axisymmetric ANDT-2F shows a J SC of 21.30 mA cm -2 , an FF of 66.21%, and a PCE of 12.13%, higher than that of centrosymmetric CNDT-2F based device. This work provides important implications for designing and synthesizing efficient organic photovoltaic materials by tuning their dipole moment. This article is protected by copyright. All rights reserved.