Perovskites are hybrid compounds made from metal halides and organic constituents. They show great potential in a range of applications, including LED lights, lasers and photodetectors, but their major contribution is in solar cells, where they are poised to take over the market from their silicon counterparts.

One of the obstacles facing the commercialization of perovskite solar cells is that their power-conversion efficiency and operational stability drop as they scale up, making it a challenge to maintain high performance in a complete solar cell.

The problem is partly due to the cell’s electron-transport layer, which ensures that electrons produced when the cell absorbs light transfer efficiently to the device’s electrode. In perovskite solar cells, the electron-transport layer is made from mesoporous titanium dioxide, which not only has a low electron mobility but is also susceptible to adverse photocatalytic events under ultraviolet light.

In a paper in Science, scientists led by Michael Grätzel at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and Dong Suk Kim at the Korea Institute of Energy Research report an innovative way for increasing the performance of perovskite solar cells, and maintaining it at a high level, even at large scales. Their innovative idea is to replace the electron-transport layer with a thin layer of quantum dots.

Quantum dots are nanometer-sized particles that act as semiconductors, and can emit light of specific wavelengths (colors) when they are illuminated. Their unique optical properties make quantum dots ideal for use in a variety of optical applications, including photovoltaic devices.

The scientists replaced the titanium dioxide electron-transport layer of their perovskite cells with a thin layer of polyacrylic acid–stabilized tin(IV) oxide quantum dots. They found that this enhanced the devices’ light-capturing capacity while also suppressing nonradiative recombination, an efficiency-sapping phenomenon that sometimes occurs at the interface between the electron-transport layer and the actual perovskite layer.

By using the quantum dot layer, the researchers found that perovskite solar cells of 0.08cm2 attained a record power-conversion efficiency of 25.7% (certified 25.4%) and high operational stability, while facilitating the scale-up. When increasing the surface area of the solar cells to 1cm2, 20cm2 and 64cm2, they measured power-conversion efficiencies of 23.3%, 21.7% and 20.6% respectively.

This story is adapted from material from EPFL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.