The current global energy crisis has emphasised the urgency to reduce our reliance on non-renewable power. Solar power is one of the best strategies for generating sustainable energy.
Solar panels are made up of photovoltaic (PV) cells, which harvest the energy of photons in sunlight to produce electricity. However, this process is currently inefficient, and much energy is lost during the conversion. Improving the photovoltaic conversion efficiency (PCE) of PV cells has therefore become a focus for solar energy research.
In a recent study, researchers from Xi’an Jiaotong–Liverpool University, and other universities from China and the UK, have used a new material, functionalised MXene, to improve the performance of PV cells.
The materials used in PV cells are vital for ensuring maximum efficiency in the conversion of solar energy to electricity, and there have been remarkable advancements in recent years.
In 2009, PV cells made out of synthetic materials called perovskites – instead of the usual silicon – were introduced and have since been the focus of much research and investment.
“Perovskite solar cells offer a cheaper and more flexible alternative to silicon, and in the last decade, the conversion efficiency of sunlight into electrical energy in these cells has significantly improved. However, the stability of perovskite cells is still an essential issue for commercialisation,” says Li Yin, lead author of the study and PhD student from the School of Advanced Technology.
“In our study, we have improved the performance of perovskite solar cells and achieved an energy conversion efficiency close to the record of maximum efficiency (25.7%). Our cells also have better moisture resistance and operational stability.”
Moving through layers
PV cells consist of several layers of different materials. When a PV cell absorbs energy from the sunlight, the energy is transferred to negatively charged particles (electrons) in the top layer. This causes the electrons to move through an electron transport layer towards a positive electrode. This movement produces a current of electricity.
The team of researchers added a newly discovered class of material called MXenes to the electron transport layer to enable electrons to move more efficiently between them. This improved the conversion of sunlight into electrical energy in perovskite cells and, therefore, the performance.
“For perovskite solar cells, choosing suitable materials to make an efficient and suitable electron transport layer is crucial to achieving high stability and conversion efficiency,” says Yin.
“At first, we added unmodified MXene to the electron transport layer, which didn’t have a big impact. However, after discussing with Dr Chenguang Liu and Dr Chun Zhao, the other authors of the paper, we realised that slightly adjusting the chemical structure of the MXene may also modify the other materials in the electron transport layer. This would reduce barriers to electron movement and improve the performance of the solar cells. We were right.”
The study, Functionalized-MXene-nanosheet-doped tin oxide enhances the electrical properties in perovskite solar cells, is published in the open-access journal Cell Reports Physical Science and can be read here.
By Huatian Jin
Photo by Alex Lang
Edited by Catherine Diamond and Patricia Pieterse