Magnesium fluoride microcavity-based non-fullerene semitransparent organic solar cells with high peak transmittance and low efficiency loss rate

Microcavity-based semitransparent organic solar cells (ST-OSCs) have become a hot issue in the research field of green energy harvesting due to their wider potential applications in colored photovoltaic glass, building-integrated photovoltaics, and so on. However, for this kind of ST-OSCs, high photoelectric conversion efficiency (PCE) and high peak transmittance cannot usually be achieved simultaneously. To circumvent the problem, this paper proposes MgF 2 microcavity with a structure of Au/Ag/MgF 2 /Ag for ST-OSCs so that high peak transmittance can be achieved at low cost of PCE. The device structure of ST-OSCs is Glass/ITO/ZnO/PTB7-Th: IEICO-4F/MoO 3 /Au/Ag/MgF 2 /Ag. By combining the high transmittance of MgF 2 microcavities with the low absorption of IEICO-4F in the blue light, a colorful ST-OSCs with high blue light transmittance can be obtained. The IEICO-4F in the active layer shows strong optical absorption in the near-infrared wavelength region, but weak absorption in the visible region. The results demonstrate that the peak transmittance of ST-OSCs reached a high value of 48% at 440 nm and the PCE reached 10.4%. Such a high peak transmittance is achieved while the PCE reduction compared to the control opaque device is about 5%. The PCE loss rate at each peak transmittance is the lowest among the reported values for the similar ST-OSCs devices. By adjusting the thickness of MgF 2 , ST-OSCs with different colors can be obtained, the peak transmittance of which is over 32% and the PCE loss rate is less than 7.25%. This report provides a new approach to solve the trade-off between efficiency and transmittance of ST-OSCs.