Semitransparent organic solar cells show attractive potential in the application of building-integrated photovoltaics, agrivoltaics, floating photovoltaics, and wearable electronics, as their multiple functionalities of electric power generation, photopermeability, and color tunability. Design and exploration of semitransparent organic solar cells with optimal and balanced efficiency and average visible light transmittance and simultaneously high stability are in great demand. In this work, based on a layer-by-layer-processed active layer and an ultrathin metal electrode, inverted semitransparent organic solar cells (ITO/AZO/PM6/BTP-eC9/MoO₃/Au/Ag) were fabricated. Optimal and balanced efficiency and average visible light transmittance were demonstrated, and simultaneously promising thermal and light stability were achieved for the obtained devices. The power conversion efficiency of 13.78–12.29% and corresponding average visible light transmittance of 14.58–25.80% were recorded for the ST-OSC devices with 25–15 nm thick Ag electrodes, respectively. Superior thermal and light stability with ~90% and ~85% of initial efficiency retained in 400 h under 85 ℃ thermal stress and AM1.5 solar illumination were demonstrated, respectively.

With rapid progress, organic solar cells (OSCs) are getting closer to the target of real application. However, the stability issue is still one of the biggest challenges that have to be resolved. Especially, the thermal stability of OSCs is far from meeting the requirements of the application. Here, based on the layer-by-layer (LBL) process and by utilizing the dissolubility nature of solvent and materials, binary inverted OSCs (ITO/AZO/PM6/BTP-eC9/MoO₃/Ag) with comb shape active morphology are fabricated. High efficiency of 17.13% and simultaneous superior thermal stability (with 93% of initial efficiency retained in ~9:00 h under 85 ℃ in N₂) are demonstrated, showing superior stability to reference cells. The enhancements are attributed to the formed optimal comb shape of the active layer, which could provide a larger D/A interface, thus more charge carriers, render the active blend a more stable morphology, and protect the electrode by impeding ion’s migration and corrosion. To the best of our knowledge, this is the best thermal stability of binary OSCs reported in the literature, especially when considering the high efficiency of over 17%.