Shedding light on perovskite solar cell materials

Solar power is considered one of the most sustainable resources for Saudi Arabia to wean itself from its dependence on oil, but existing technologies for converting the sun’s energy into electricity remain relatively expensive and inefficient. Researchers from KACST’s National Center for Petrochemicals Technology are helping to develop a new kind of perovskite-based solar cell that could outperform the more expensive silicon-based cells used in most commercial solar panels today.  

A team, led by researchers at École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, has conducted direct comparisons of different takes on this next-generation, photovoltaic technology. In two new studies, they show which compositions of perovskite solar cell (PSC) are most efficient at capturing the Sun’s energy; findings that the authors say “will pave a way to further improve the performance of PSCs.”

The name perovskite comes from a mineral discovered almost 200 years ago in the Ural Mountains of Russia. However, the term has come to describe a range of compounds that all share its crystal structure. That means perovskites can be made from a range of different materials, and the challenge for scientists is to find the best ones for converting light into electric current. 

A team that included Mohammad Hayal Alotaibi, head of KACST’s Joint Center of Excellence in Integrated Nanosystems, compared the power conversion efficiencies of different types of PSCs. In their first study¹, the researchers looked at two PSCs that both involved lead and bromide. One also included caesium ions, while the other had a layer of another positively charged molecule called formamidinium. 

With funding support from KACST, Alotaibi and his collaborators, including EPFL electrochemist, Michael Grätzel, measured current losses, storage capacity, charge transport and other characteristics of the materials to dissect the fundamental electronic processes occurring in these two PSCs. They showed that the formamidinium-based PSCs carried their charge more efficiently without losing as much energy as the caesium-based ones. 

Although the measurements were taken under a controlled laboratory set-up, the authors conclude that the physical properties documented for these formamidinium-based PSCs should result in improved performance in the field, where more stable photovoltaic technologies are urgently needed to withstand the hot and humid conditions of the Saudi desert. 

In the second KACST-backed study², Alotaibi again worked with Grätzel and others to investigate the possibility of adding caesium or rubidium to PSCs that contain a backbone of lead, iodide and methylammonium. In this case, the addition of caesium reduced the photovoltaic performance of the material, and rubidium didn’t even integrate into the three-dimensional lattice. It follows that neither metal ion may offer any enhancement to this particular PSC material.

1. Yadav, P., Alotaibi, M.H., Arora, N., Dar, M.I., Zakeeruddin, S.M. & Grätzel, M. Influence of the nature of A cation on dynamics of charge transfer processes in perovskite solar cells. Advanced Functional Materials 28, 1706073 (2018).| article

   2. Uchida, R., Binet, S., Arora, N., Jacopin, G., Alotaibi, M.H., et al. Insights about the absence of Rb cation from the 3d perovskite lattice: Effect on the structural, morphological, and photophysical properties and photovoltaic performance. Small 14, 1802033 (2018). |  article