The potential of a class of materials called perovskites to enable solar cells to better absorb sunlight for energy production is widely known. However, this potential has yet to be fully realised, particularly under real-world operating conditions. 

New research published last month in the Nature Energy, has revealed defects in a popular perovskite light absorber that impede solar cell performance.

 The researchers found a change in the nature and density of these ‘intragrain planar defects’ correlated with a change in solar cell performance. 

The discovery by an international team of researchers, led by Monash University and Wuhan University of Technology, could lead to improved solar cell technology and provide another step towards reducing the use of fossil fuels for energy. 

Perovskite light absorbers have the potential to improve the efficiency of established silicon solar cells by adding an additional layer that can absorb colours, or parts of the energy spectrum, of sunlight which current silicon solar cells cannot. 

The highest possible performance of silicon solar cells is around 32 per cent of capacity. This means only about 32 per cent of the energy available in sunlight can be captured by silicon solar cells.

Placing such a perovskite solar cell on top of a silicon solar cell, known as a tandem solar cell, can effectively boost the overall performance of the stack up to roughly 42 per cent. 

Since small changes to the perovskite composition can tune the absorption spectrum of perovskite solar cells relatively easily, it is possible to create a perovskite solar cell that absorbs the higher energy light but lets the lower energy light pass through. 

The research team used the imaging and diffraction protocol developed at the Monash Centre for Electron Microscopy (MCEM) to study the crystal structure of a range of perovskite solar cell materials in their pristine state. 

Lead corresponding author, Professor Joanne Etheridge, director of the MCEM and Professor in the Department of Materials Science and Engineering, said disruptions in the periodic crystal structure can have a strong influence on the material’s electronic properties. 

“Being able to map the local crystal structure of a thin film of perovskite light absorber and correlate this with the overall solar cell device performance provides exciting new insights into how device performance can be improved,” Professor Etheridge said. 

Lead author, Dr Wei Li from the Wuhan University of Technology said to make a good solar cell, a material must be able to transform sunlight into electricity efficiently and do so outdoors for many decades.

The research opens new avenues for improving perovskite solar cell performance