A technique that improves the performance and stability of next-generation solar cells – without adding any chemicals or coatings – has been demonstrated by researchers from Korea University and the University of Surrey.

The study, which has been published in Nature Energy, details a method that works by placing two types of perovskite film in contact with each other. That contact alone triggers a molecular interaction at the interface, which reorganises the crystal structure of the light-absorbing layer throughout its entire depth. The result is a more ordered, more durable material that converts sunlight into electricity more efficiently.

Solar cells built using the technique achieved a certified power conversion efficiency of 25.61 per cent, independently verified by the Solar Energy Research Institute of Singapore.

Perovskite solar cells have attracted significant research interest because they are cheaper and easier to manufacture than conventional silicon-based panels. Their commercial potential has been limited, however, by questions over how well they hold up under the heat and humidity conditions of real-world deployment.

Under accelerated ageing tests, the treated material required roughly twice the thermal energy to degrade compared with comparable materials reported in recent literature – a meaningful improvement in a field where long-term stability is the central challenge.

Dr Jae Sung Yun, co-author of the study and nanoscale imaging expert from the University of Surrey’s Advanced Technology Institute, said:

"Perovskite solar cells could genuinely change how we generate electricity – they are cheaper to make than silicon panels and the efficiency numbers are now very competitive. The stumbling block has always been durability. What I find exciting about this work is how elegantly simple the solution turns out to be. You place two films in contact, and that contact alone reorganises the material at a molecular level confirmed by our state-of-the-art nanoscale chemical imaging techniques – all the way through, not just at the surface. No extra chemicals, no added complexity. ”

The technique works through what the researchers call contact-triggered cationic interaction (CCI). When two perovskite films are placed in physical contact, molecular forces at the interface cause the charged particles – cations – within the light-absorbing layer to adopt a more uniform, aligned arrangement. This reduces the structural defects that cause energy to be lost as heat rather than converted to electricity. The time that charge carriers survive before recombining, a key measure of solar cell quality, increased from 4.48 to 5.89 microseconds in treated material compared with untreated controls.

To confirm this, the Surrey team used photo-induced force microscopy (PiFM) – a technique that maps chemical signatures at the nanoscale by combining the high resolution of atomic force microscopy with infrared spectroscopy, bypassing the diffraction limit of light. This allowed the researchers to visually validate the precise, uniform formation of chemical bonds triggered by the CCI process, confirming that the molecular alignment occurred exactly as predicted at the film interface.

Professor Ravi Silva, Director of the Advanced Technology Institute at the University of Surrey, said:

"What this study demonstrates is that you can meaningfully improve both the efficiency and the durability of perovskite solar cells without adding a single extra chemical or processing step – just by controlling how two films interact at the point of contact. That is a genuinely elegant result, and the performance numbers back it up. This kind of advance matters because stability under real-world conditions is the central challenge the field has to solve before perovskites can be deployed at scale. It connects directly to the work we are doing here at Surrey through our £2.7 million EPSRC programme on scaling perovskites across large-area flexible substrates – where durability is not a nice-to-have but a requirement. Research like this brings that goal closer."