Summary:
UCLA researchers in the Department of Materials Science and Engineering have invented a series of hole transporting materials that have enabled among the highest recorded power conversion efficiencies for perovskite solar cells while maintaining high device stability and low cost.
Background:
Perovskite solar cells (PSCs) are an emerging type of thin-film solar cell that are a promising replacement to state-of-the-art crystalline silicon as well as other thin-film solar technologies because they are inexpensive and simple to manufacture. PSCs are largely in the early stages of commercialization. Power conversion efficiencies (PCEs) of conventional PSCs have been approaching those of cutting-edge crystalline-silicon solar cells. However, the commercial adoption of this technology is limited by the poor stability of the perovskite material and the charge-transport layers. The hole transporting layer (HTL), one type of charge-transport layer, plays a significant role in the efficiency and stability of PSCs. The conventional inorganic HTLs, which are typically metal oxides, demand high-temperature annealing, thus limiting their practical implementation. HTL materials in use today have also demonstrated poor thermal and photo stability. Thus, for PSCs to emerge as a practical alternative to the commercially available products, a novel hole transporting material is needed to improve the device stability without sacrificing photovoltaic efficiency.
Innovation:
Professor Yang and his research team have successfully synthesized a series of low cost and stable materials that can be used as the hole transporting layer of a perovskite solar cell. Testing showed an impressive PCE of 23.77% for a PSC made of their charge-transfer materials. The tests have shown that simple chemical modifications of this new material can further improve the device efficiency, address the trade-off between solubility and the subsequent deposition processes, and be more optimal for perovskite growth. The inventors have also successfully prototyped and tested the solar cells in devices that demonstrated 5 times greater thermal stability (over 2000 hours) than that of the reference devices and retained over 82.7% efficiency at 85°C. In addition, the UCLA device was able to maintain over 80% of its initial PCE for over 2000 hours, while the reference device was completely degraded after 350 hours. These materials can be tailored to meet the specific requirements of certain photovoltaic technologies, and the solvent resistance and morphological stability of the device are expected to be improved even further.
Potential Applications:
• Hole transporting layer material for perovskite solar cells
• Interfacial layer for photovoltaic technologies
• Buffer layer to suppress the ion migration in perovskite-based applications
Advantages:
• Enhanced photovoltaic performance
Reaches PCE of 23.77%
• Improved thermal stability, 5X
Retains 82.7% of the initial PCE for over 2000 hrs.
• Improved photochemical stability, ~ 5.7X
Retains 80.3% of the initial PCE for over 2000 hrs.
• Tunable hydrophobicity and hydrophilicity
• Beneficial towards various photovoltaic technologies (perovskite; perovskite-silicon; perovskite-CIGS, etc.)
Development to Date:
First successful demonstration (first actual reduction to practice): June/04/2022.
Reference: UCLA Case No. 2023-087
Lead Inventors: Prof. Yang Yang; Dr. Dong Meng.