Unlike conventional silicon-based solar cells, perovskite solar cells (PSCs) are not only thin and lightweight, but can also be seamlessly applied to curved surfaces, like building facades and vehicle roofs. What’s more, they can be easily manufactured at room temperature using a solution process, leading to significantly reduced production costs.

However, for PSCs to achieve commercialization, it is crucial to develop technologies that maintain high efficiency over extended periods. A research team affiliated with UNIST has successfully made strides in this area. Their work is published in the journal Joule.

Professor Sang Il Seok of the School of Energy and Chemical Engineering at UNIST, along with researchers Jongbeom Kim and Jaewang Park, has developed an interlayer that leverages the specificity of organic cations on the surface of PSCs, simultaneously achieving high-efficiency and durability.

PSCs utilize a material known as perovskite as the light-absorbing layer. These cells generate electrical energy by transferring charge carriers created when the light-absorbing material absorbs sunlight to the electrodes. Minimizing defects in this light-absorbing material is essential for effectively delivering charges to the electrodes and enhancing cell efficiency.

Previously, research focused on the use of single organic cations, which posed challenges such as structural collapse of the thin films due to the migration of individual cations and energy level misalignment. Energy levels serve as a “staircase” pathway for charge movement; if the interlayer energy levels are misaligned, charge losses can occur, leading to reduced efficiency.

To address this issue, the research team employed a dual cation approach to design a thermally stable interlayer. By exploiting the differing intermolecular interactions of two types of organic cations, they stabilized the interface structure and naturally aligned the energy levels conducive to efficient hole transport. Additionally, the concentration of defects within the perovskite thin film was significantly decreased, leading to a marked improvement in charge retention.

The PSCs incorporating this interlayer technology achieved an impressive power conversion efficiency (PCE) of 26.3%, rivaling the highest efficiencies of commercial silicon cells. This achievement was recognized by the U.S. National Renewable Energy Laboratory in 2023, which validated a world record efficiency of 25.82% for the technology. Furthermore, when stored at room temperature for 9,000 hours, the cells maintained close to 100% of their original performance, demonstrating exceptional long-term stability.

Jongbeom Kim commented, “This technology signifies a remarkable advancement as it enables the formation of a stable interlayer through a simple solution process, simultaneously improving the durability and manufacturing efficiency of PSCs. The innovative combination of organic ammonium cations holds immense potential.”

Building on this research, the team aims to develop PSCs that exceed 28% efficiency while maintaining high durability and plans to continue their efforts toward the commercialization of this technology.