Performance Improvement of Low-Band-Gap Polymer Solar Cells by Optical Microcavity Effect

We investigate the performance of the indium tin oxide (ITO)-free low-band-gap polymer solar cells (PSCs) with a WO 3 /Ag/WO 3 multilayer as a transparent electrode. For the device with a 60-nm-thick active layer, the efficiency is improved by 26.5% when compared with that of the device with an ITO electrode. The improvement can be attributed to the resonance effect of the microcavity structure occurring between the transparent WO 3 /Ag/WO 3 and top metal electrode. Further investigation based on the incident photon-to-electron conversion efficiency spectra test and transfer matrix simulation is performed to expatiate on the effects of the microcavity on the performance of the low-band-gap PSCs with the WO 3 /Ag/WO 3 multilayer as the transparent electrode.