Highly Stable Organic Solar Cells Based on an Ultraviolet-Resistant Cathode Interfacial Layer

Although the photovoltaic efficiency of organic solar cells (OSCs) has exceeded 17%, poor lifetime excludes OSCs from practical use. In particular, UV rays in sunlight may cause the decomposition of organic photovoltaic materials, which has been proved to be the main reason for the efficiency decay. At present, there is still no effective approach to substantially improve the device stability. Herein, we fabricate a highly efficient OSC with exceptional stability under sunlight illumination by incorporating a UV-resistant cathode interlayer (CIL), namely (sulfobetaine-N,N-dimethylamino)propyl naphthalene diimide (NDI-B). NDI-B was designed and synthesized based on the naphthalene diimide (NDI) unit, thereby exhibiting excellent capability of electron collection. Moreover, NDI-B shows strong absorption in the UV region and has good UV resistance. Devices using NDI-B as a CIL exhibited a photovoltaic efficiency of 17.2%, representing the state-of-the-art photovoltaic performance of OSCs. Notably, the NDI-B-modified OSC exhibited a T80 of over 1800 h under full-sun AM 1.5 G illumination (100 mW cm(-2)), which represents the best stability for OSCs. We demonstrate that the unique ability of the NDI-B interlayer to convert UV light to an additional photocurrent can effectively protect photovoltaic materials from UV-induced decomposition, which is the key to obtain high OSC stability under operational conditions. [GRAPHICS] .

Automated summary

Although organic solar cells (OSCs) have achieved high photovoltaic efficiency, their practical use is limited by poor lifetime due to material decomposition caused by UV radiation. In this study, researchers have successfully fabricated highly efficient and exceptionally stable OSCs by incorporating a UV-resistant cathode interlayer (NDI-B) to protect the photovoltaic materials from UV-induced decomposition.