A team from Yale University has discovered a modification of perovskite that can increase the stability and efficiency of perovskite solar cells.

The team explained that light usually generates an exciton in most semiconductor materials, a state where an electron is bound to an electron hole via an electrostatic force. In order to produce usable electricity, the bound electron-hole pair has to be separated into a free electron and free electron hole. This is usually done by electron acceptors, which can overcome the binding energy holding the electron-hole pair together. However, since perovskite semiconductors possess exciton binding energies as low as 16 meV, they generally do not require the use of electron acceptors, which eases the process of generating electricity.

In a recent study, EPFL researchers demonstrated how light affects perovskite film formation in solar cells. The team showed that, in the two most common methods used today, light can greatly accelerate the formation of perovskite films and control the morphology of their crystals, influencing the efficiency of the resulting solar cell.

The team used confocal laser scanning fluorescence microscopy and scanning electron microscopy to examine how direct light affects the crystal formation when depositing perovskites in layers, a common stage in building a solar cell. The goal is to ensure homogeneity across the perovskite film, as this is linked to superior photovoltaic performance.

Researchers from Sun Yat-Sen University in China have created a composite of perovskite quantum dots and graphene oxide that can reduce CO₂ when stimulated with light. It is referred to as the first known example of artificial photosynthesis based on perovskite quantum dots.

The team prepared quantum dots – semiconductor nanoparticles – of a highly stable cesium–lead halide perovskite, as well as a composite material made of these quantum dots and graphene oxide. Both materials showed an efficient absorption of visible light and strong luminescence. The team used these products to achieve a fundamental step in artificial photosynthesis – the reduction of CO₂. To simulate sunlight, they used a xenon lamp with an appropriate filter.