Adding “self-healing” polymer may prevent lead leakage

Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have found that a protective layer of epoxy resin helps prevent the leakage of pollutants from perovskite solar cells (PSCs). Adding a “self-healing” polymer to the top of a PSC can drastically reduce how much lead it discharges into the environment. This may give a boost to prospects for commercializing the technology.

A protective layer of epoxy resin helps prevent the leakage of pollutants from perovskite solar cells

“Although PSCs are efficient at converting sunlight into electricity at an affordable cost, the fact that they contain lead raises considerable environmental concern,” explains Professor Yabing Qi, head of the Energy Materials and Surface Sciences Unit, who led the study. "While so-called ‘lead-free’ technology is worth exploring, it has not yet achieved efficiency and stability comparable to lead-based approaches. Finding ways of using lead in PSCs while keeping it from leaking into the environment, therefore, is a crucial step for commercialization.”

Lead-free halide double perovskites successfully made to emit warm white light

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.

Lead-free halide double perovskites successfully made to emit warm white light image

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.

KAIST team proposes lead-free, efficient perovskite material for photovoltaic cells

A KAIST research team has proposed a perovskite material, Cs2Au2I6 that serves as a potential active material for highly efficient lead-free thin-film photovoltaic devices. This material is expected to lay the foundation to overcome previously known limitations of perovskite including its stability and toxicity issues.

KAIST team proposes lead-free, efficient perovskite material for photovoltaic cells image

The joint team led by Professor Hyungjun Kim from the KAIST Department of Chemistry and Professor Min Seok Jang from the School of Electrical Engineering analyzed a previously discovered perovskite material, Cs2Au2I6, consisting of only inorganic substances and investigated its suitability for application in thin-film photovoltaic devices. Theoretical investigations suggests that this new perovskite material is not only as efficient but also more stable and environment friendly compared to the conventional perovskite materials.

Chinese team develops lead-free perovskite photodetector with excellent sensitivity

A research team at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences has fabricated a sensitive photodetector based on lead-free perovskite single crystals.

Chinese team develops lead-free perovskite photodetector image

"We have developed a high performance photodetector based on MA3Sb2I9 microsingle crystals (MSCs)," said Prof. HAN. Scientists found that MA3Sb2I9 single crystals exhibited a low trap-state density of ~1010 cm-3, high carrier mobility of 12.8 cm2 V-1 s-1 and long carrier diffusion length reaching 3.0 μm.

Progress towards lead-free perovskite solar cells

Researchers from Sweden's Linköping University and the Nanyang Technological University (NTU) in Singapore have developed high-quality films based on double perovskites, which demonstrate promising photovoltaic properties. Developing environmentally friendly perovskites has become important in solving the toxicity issue of lead‐based perovskite solar cells.

Lead-free double perovskite imageThe lead-free double perovskite solar cells (yellow, in the front) compared with the lead-based device (dark, in the background)

"Our colleagues at Nanyang Technological University in Singapore have shown that the charge carriers demonstrate long diffusion lengths in the material, which is necessary if the material is to be appropriate for the application of in solar cells," says the Linköping team.