Comparing the Indoor Efficiencies of Organic Solar Cells Based on the Solution‐Processed and Thermally Evaporated Anode‐Modifying Layers

The photovoltaic performances of organic solar cells (OSCs) using solution‐processed poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and thermally evaporated MoO 3 for the anodic modification have been characterized and modeled under both 1 sun AM 1.5G and indoor illuminations. The MoO 3 decreases the energetic disorder of active layer than PEDOT:PSS, attributed to that the p ‐doping effect of MoO 3 in donor generates a certain number of free holes and thereby suppresses the subgap absorption of active layer. The device with MoO 3 shows much bigger shunt resistance than the one with PEDOT:PSS under indoor light, because neither MoO 3 nor PEDOT:PSS gets markedly photoexcited under indoor light, but the MoO 3 has smaller excess free volume and thereby better inhibits the formation of the parallel paths than PEDOT:PSS. As a result, the MoO 3 enables higher indoor efficiencies than the PEDOT:PSS. The current research indicates that the anode‐modifying layers with high work function, small excess free volume, and high visible‐light transparency are desirable for making highly efficient OSCs for the indoor applications.