| Work Detail |
A Saudi-Chinese research team has fabricated a perovskite-silicon tandem solar cell without a hole transport layer (HTL) in the perovskite top cell. This innovative strategy, based on the co-deposition of copper(I) thiocyanate and perovskite in the absorber of the top cell, was intended to solve the typical problems of HTL in tandem devices.
An international research team has fabricated a 1 cm2 perovskite-silicon tandem solar cell that uses a superior cell based on a perovskite absorber integrating inorganic copper(I) thiocyanate (CuSCN).
“First, a co-deposition strategy of CuSCN and perovskite has been developed to solve the key technical challenge of fabricating a perovskite top cell on textured silicon bottom cells,” corresponding author of the research, Xingbo Yang, explained to pv magazine . “Furthermore, inorganic CuSCN is also applied for the first time in perovskite/silicon tandem solar cells, and the resulting devices demonstrate outstanding stability to light and moist heat.”
The researchers explained that they decided to build the top cell without a hole transport layer (HTL) because HTLs used in top cells of tandem devices often suffer from defects caused by nonconformal deposition or dewetting. They deposited the CuSCN-containing perovskite precursor ink directly onto the indium tin oxide (ITO) recombination layer of a heterojunction (SHJ) bottom cell with an efficiency of 24.42%.
“Our method has been confirmed to enable the formation of local hole-collecting contacts by embedding CuSCN into the device, resulting in a device structure different from that of a common, classical pin configuration based on a thin self-assembly monolayer (SAM) on recombination layers such as ITO,” Yang explained.
The scientists built the top cell with an ITO substrate, silicon monoxide-based passivating contacts (poly-SiOx), the embedded CuSCNE perovskite absorber, a tin oxide (SnO2) layer, a Buckminster fullerene (C60) electron transport layer (ETL), and a magnesium fluoride (MgF2)-based antireflective coating.
In this cell configuration, the CuSCN phase embedded in the perovskite grain boundaries acts both as an efficient hole-collecting local contact and as a defect passivator. “We verified that CuSCN aggregates at some depth at the grain boundaries of the buried perovskite surface, forming local hole-collecting contacts for efficient hole transfer and grain boundary passivation,” the researchers emphasize.
Tested under standard lighting conditions, the tandem device achieved a power conversion efficiency of 31.46%. It was also able to retain 93.8% of the initial efficiency after approximately 1,200 h of maximum power point tracking at 45°C, and 90.2% after more than 1,000 h of damp heat testing at 85°C and 85% relative humidity.
“To be commercially valuable, the scaling of tandem devices with 4 cm2 aperture area realized by both spin coating and wafer coating has been verified, demonstrating competitive aperture power conversion efficiencies of 28.14% and 25.23%, respectively,” Yang added. “This indicates the high scalability and universality of our co-deposition method.”
The device was presented in the study, “ Efficient and stable perovskite-silicon tandem solar cells with copper thiocyanate-embedded perovskite on textured silicon,” published in Nature Photonics . The research team consisted of scientists from Soochow University, Zhejiang University, and the Hong Kong Polytechnic University in China, as well as King Abdullah University of Science and Technology (KAUST) in Saudi Arabia and Chinese PV manufacturing equipment supplier Maxwell Technologies. |
