Guiying Xu

A Semitransparent Inorganic Perovskite Film for Overcoming Ultraviolet Light Instability of Organic Solar Cells and Achieving 14.03% Efficiency

Organic solar cells (OSCs) can be unstable under ultraviolet (UV) irradiation. To address this issue and enhance the power conversion efficiency (PCE), an inorganic-perovskite/organic four-terminal tandem solar cell (TSC) based on a semitransparent inorganic CsPbBr3 perovskite solar cell (pero-SC) as the top cell and an OSC as bottom cell is constructed. The high-quality CsPbBr3 photoactive layer of the planar pero-SC is prepared with a dual-source vacuum coevaporation method, using stoichiometric precursors of CsBr and PbBr2 with a low evaporation rate. The resultant opaque planar pero-SC exhibits an ultrahigh open-circuit voltage of 1.44 V and the highest reported PCE of 7.78% for a CsPbBr3 -based planar pero-SC. Importantly, the devices show no degradation after 120 h UV light illumination. The related semitransparent pero-SC can almost completely filter UV light and well maintain photovoltaic performance; it additionally shows an extremely high average visible transmittance. When it is used to construct a TSC, the top pero-SC acting as a UV filter can utilize UV light for photoelectric conversion, avoiding the instability problem of UV light on the bottom OSC that can meet the industrial standards of UV-light stability for solar cells, and leading to the highest reported PCE of 14.03% for the inorganic-perovskite/organic TSC.

Molecular design with silicon core: toward commercially available hole transport materials for high-performance planar p–i–n perovskite solar cells

Organic hole transport layers (HTL) play a very important role for realizing high performance and low-cost planar p–i–n perovskite solar cells (pero-SCs). In this work, we synthesized two X-shaped organic HTL materials, Si-OMeTPA and SiTP-OMeTPA, with silicon cores and triphenylamine (TPA) derivative branches. This molecular design strategy can substantially simplify synthetic procedures making them available for reducing device costs. This is particularly applicable for Si-OMeTPA since it can be synthesized by two steps from commercial raw materials showing a total yield of over 60%. This molecularly designed Si-OMeTPA possesses advantages of high thermal stability, high crystallinity with a long range ordered lamellar structure, and excellent hole mobility. The resulting HTL can also facilitate the sequential growth of high-quality perovskite films, giving a significantly enhanced photovoltaic performance with a best power conversion efficiency of 19.06%, which is one of the highest PCE among the planar p–i–n pero-SCs to date. In addition, the devices exhibit negligible hysteresis, good reproducibility, and stability. To the best of our knowledge, this is the first example of an easily synthesized HTL material in planar p–i–n pero-SCs that shows superior performance relative to the well-known poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) HTL.