Stability

Researchers at the University of California, Los Angeles have used a polymer film to reduce defects in the light-absorbing perovskite, producing solar cells that are efficient and relatively robust.

The team explains that perovskites usually used in solar cells typically contain an organic cation and lead halide anions. But the heat treatment used to convert the perovskite’s precursors into a crystalline layer can also drive out some of these organic cations. This leaves defects in the material’s structure that hamper its performance and potentially make it less stable to moisture, heat, and even sunlight itself.

Researchers at Huazhong University of Science and Technology (HUST) in China, University of Toledo in the U.S, Monash University in Australia, Jilin University and Tsinghua University in China, the Dalian Institute in China and the University of Toronto in Canada have examined a lead-free double perovskite that exhibited stable and efficient white light emission. In its mechanism of action, the material produced self-trapped excitons (STEs) due to Jahn-Teller distortion of the AgCl₆ octahedron in the excited state of the complex, observed when investigating exciton-phonon coupling in the crystal lattice.

The research team stated that a fifth of global electricity consumption is based on lighting, and efficient and stable white-light emission with single materials is ideal for such applications. Photon emission that covers the entire visible spectrum is, however, difficult to attain with a single material. Metal halide perovskites, for instance, have outstanding emission properties but contain lead, and so yield unsatisfactory stability. The perovskite in this study is, therefore, lead-free.