Investigating the shunt resistance of semitransparent organic solar cells via simulating their practical photovoltaic performances

Abstract

Semitransparent organic solar cells (ST-OSCs) have promising application in building-integrated photovoltaics, because they convert solar light into electricity and simultaneously allow for the transmission of visible light. The trade-off between power conversion efficiency (PCE) and average visible transmittance (AVT) governs the light utilization efficiency (LUE) of ST-OSCs. Therefore, improving the PCE without sacrificing the AVT is crucial to enhance the LUE of ST-OSCs. Here, the shunt resistance (RSH) of ST-OSCs has been derived via simulating their practical photovoltaic performances. It is found that the RSH of the latest ST-OSCs with practical LUEs of 5-6% is around 94-170 Ω cm2, about 1/26 to 1/7 times that of their opaque counterparts; this is because the diffusion of semitransparent cathode through active layer is much severer than that of opaque cathode through active layer, generating more parallel paths in ST-OSCs than in opaque OSCs. The small RSH leads to a big loss of short-circuit current density of ST-OSCs. A LUE of 8.51% has been predicted with RSH=600 Ω cm2 and AVT=49.62%, markedly higher than the practical one of 6.05% with RSH=100.2 Ω cm2 and AVT=49.62%. The current research indicates that the very low RSH is the key factor limiting the LUE of ST-OSCs in the electrical aspect.