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

Abstract

Semitransparent organic solar cells (ST-OSCs) have promising applications in building-integrated photovoltaics, because they convert solar light into electricity and simultaneously allow for the transmission of visible light. The trade-off between the 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 enhancing the LUE of ST-OSCs. Here, the shunt resistance (R_SH) of ST-OSCs has been derived via simulating their practical photovoltaic performance. It is found that the R_SH values of the latest ST-OSCs with practical LUEs of 5–6% are around 94–170 Ω cm², about 1/26 to 1/7 of those of their opaque counterparts; this is because the diffusion of a semitransparent cathode through the device is much more severe than that of an opaque cathode through the device, generating more parallel paths in ST-OSCs than in opaque OSCs. Small R_SH values lead to a big loss of short-circuit current density in ST-OSCs. A LUE of 8.51% has been predicted with R_SH = 600 Ω cm² and AVT = 49.62%, markedly higher than the practical value of 6.05% with R_SH = 100.2 Ω cm² and AVT = 49.62%. The current research indicates that very low R_SH values are the key factor limiting the LUEs of ST-OSCs from an electrical aspect.