Theoretical Investigation of Polarization-Sensitive Photoresponse in the Donor-Acceptor Interface of Organic Photovoltaic Devices

Understanding the photoelectric conversion process is of great significance for the design and preparation of organic photovoltaic devices. In this work, we investigated the intermolecular and intramolecular photoelectric conversion processes and charge transfer characteristics of donor (D) and acceptor (A) materials at the molecular level by using simulation methods. The nonequilibrium Green’s function method is used to calculate the photocurrents excited by incident photons with different polarization directions. The results show that the photocurrents are optical anisotropy, and the maximum responsivity appears along the specific direction that depends on the incident photon energy. The polarization-sensitive photocurrents are attributed to the anisotropic distribution of photogenerated electrons and holes. Moreover, the integrated photocurrents decrease exponentially with the increase in the π-π stacking distance. However, for the photoexcitation by photons with specific energy, such as 1.18 eV, the photocurrents would increase at first and then decrease as the stacking distance increases; this is due to the energy level splitting caused by the π-π stacking of donor and acceptor molecules. This study proposes a new perspective for understanding photoresponse of the D/A interface, which provides theoretical insights for the advancement of polarized light detection and organic optoelectronics.