Improving the efficiency of organic photovoltaic cells by introducing an ultrathin modification layer with a strong dipole moment

A method to improve the efficiency of organic photovoltaic cells through inclusion of an ultrathin modification layer of Al₂O₃ or LiF sandwiched between poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) and indium tin oxide layers is developed. Because of the strong dipole moments of LiF and Al₂O₃, either can enhance the built-in electric field, which increases the probability of the carriers reaching the corresponding electrode. In addition, the low work function of PEDOT:PSS can decrease the energy barrier for carrier transmission. A 21.7% improvement in the power conversion efficiency of experimental devices was achieved, mainly because the short circuit current was enhanced by almost 30%.