A semitransparent organic solar cell with a bifacial factor of 99.1%

Semitransparent organic solar cells (ST-OSCs) based on silver nanowires (AgNWs) top electrodes have attracted significant interest due to their high transmittance and high electrical conductivity characteristics and showed great potential in the field of building integrated photovoltaics (BIPVs). However, the deposition of AgNWs will partially damage the underlying electron transporting layer (ETL), leading to poor interfacial performance. Thus, the efficiency of ST-OSCs based on AgNWs still lags behind those based on ultrathin metal electrodes. This work develops a bilayer ETL combining zinc oxide nanoparticles (ZnO) and PDINN to improve the interface between the active layer and the top electrode. The best-performing semitransparent device achieves a remarkable 12.5% power conversion efficiency (PCE) with an average visible light transmittance (AVT) of 22.9%. By adjusting the acceptor-to-donor ratio and concentration of the active layer, the ST-OSC can achieve the highest light utilization efficiency (LUE) of 4.0% with a PCE of 9.5%. Furthermore, by optimizing the top electrode and active layer, a bifacial factor of 99.1% is achieved for the ST-OSCs, which is the highest reported bifacial factor so far. This work provides a promising pathway to develop high-efficiency ST-OSCs for the application of BIPVs.