Korean Researchers Develop Design To Boost Back-Contact Perovskite Cell Performance

Researchers from South Korea have developed a new interface engineering strategy that significantly improves the efficiency and stability of back-contact perovskite solar cells, a next-generation solar technology seen as a promising alternative to conventional designs.

The research team, led by Associate Professor Min Kim of the University of Seoul and doctoral researcher Dohun Baek of Jeonbuk National University, has introduced a novel bilayer tin oxide (SnO₂) electron transport layer that reduces charge recombination losses and enhances power conversion efficiency.

Back-contact perovskite solar cells place electrical contacts at the rear of the device, allowing the light-absorbing perovskite layer to face incoming sunlight directly. This architecture improves light absorption and energy conversion compared with traditional front-contact solar cells, where electrodes and transport layers partially block incoming light. However, longer charge-transport pathways in back-contact designs increase the risk of interfacial defects and efficiency losses.

Specialised Design 

To address this challenge, the researchers engineered a bilayer SnO₂ electron transport layer using a simple spin-coating process. The bilayer combines a nanoparticle-based SnO₂ layer with a sol-gel SnO₂ layer, improving interfacial contact and energy alignment while suppressing charge recombination.

“We selected SnO₂ due to its favourable band alignment with perovskite and higher electron mobility compared to conventional titanium oxide,” Kim said. “The bilayer structure enhances charge extraction and reduces losses at the interface.”

The team compared three device configurations — colloidal SnO₂, sol-gel SnO₂, and the bilayer SnO₂ structure — fabricated on indium tin oxide substrates. Devices using the bilayer design delivered the best performance, achieving an average photocurrent of 33.67 picoampere, compared with 26.69 picoampere for sol-gel SnO₂ and 14.65 picoampere for colloidal SnO₂ devices.

Bilayer Device 

The bilayer device also recorded the highest power conversion efficiency at 4.52% and showed improved operational stability, which the researchers attributed to better suppression of charge recombination.

The findings were published online on July 4, 2025, and later appeared in Volume 654 of the Journal of Power Sources on October 30, 2025.

Baek said the results could accelerate the commercial development of back-contact perovskite solar cells, particularly for flexible devices and large-area solar modules, as the technology moves closer to real-world deployment.