Semitransparent organic solar cells based on PffBT4T-2OD with a thick active layer and near neutral colour perception for window applications

Semitransparent organic solar cells (STOSCs) are of great interest in both academic and industrial fields since they can be easily used as building windows to achieve solar power generation in building facades. However, many studies only focused on the optimisation of photocurrent generation and light transmission and ignored the colour-fidelity of devices. Meanwhile, many reported semitransparent organic solar cells require a very thin active layer around 100 nm which makes it difficult for them to be applied to large-scale window applications. Herein, we reported STOSCs with neutral color perception based on a PffBT4T-2OD:PC71BM thick active layer for the first time. We optimized the active layer thickness of the device from 300 nm to 120 nm to obtain the best performance. As a result, semitransparent devices showed a decreasing PCE and increasing AVT with the reduction of the active layer thickness. All semitransparent devices showed an excellent color rendering index above 90. The semitransparent device with an active layer thickness of 250 nm exhibits the best performance among all devices which corresponds to a considerable PCE of 6.60%, AVT of 16.3% and CRI of 90.7. This reveals that the PffBT4T-2OD:PC71BM based semitransparent devices with a thick active layer are suitable for application in building windows in terms of color perception and large-scale fabrication.