Researchers in China have fabricated a perovskite-silicon tandem solar cell that uses an indium oxide sputter buffer layer to protect the perovskite absorber and electron transport layer from potential damage due to the electrode deposition process. The new layer not only provided this protection, but also exhibited strong optical and electrical properties.
Researchers at Northwestern Polytechnical University in China have fabricated a semi-transparent perovskite-silicon tandem four-terminal solar cell (4T) based on an upper perovskite cell containing an indium oxide (In2O3) sputter buffer layer (SBL) deposited via a low-cost approach for industrial applications.
SBLs are used in perovskite-silicon tandem devices to prevent bombardment damage during transparent electrode deposition of indium tin oxide (ITO), thereby protecting the underlying perovskite absorber and electron transport layer (ETL).
“The In2O3 SBL was manufactured using the e-beam evaporation technique, a solvent-free process compatible with industrial production,” said the study’s lead author Li Can. pv magazine. “The optical and electrical properties of the In2O3 film showed a strong dependence on the deposition rate. A higher deposition rate resulted in In-rich In2O3 films with poor transmission and increased parasitic absorption. By optimizing the deposition rate we achieved stoichiometric In2O3 films, with high permeability and robust protective properties.”
The research team built the top perovskite device with a substrate of glass and ITO, a self-assembling monolayer (SAM) made of nickel(II) oxide (NiO), the perovskite absorber, an ETL that relies on buckminsterfullerene (C60), A bathocuproin (BCP) buffer layer, the In2O3 SBL and the ITO electrode.
This cell achieved an energy conversion efficiency of 20.20%, which the scientists say is close to that of its opaque counterpart, while also showing excellent electrical, optical and protective properties of the In2O3 layer, with an energy bandgap of 1.68 eV.
“In2O3 20 nm thick films effectively protected the underlying perovskite film and ETL from bombardment damage during ITO sputtering,” Can explained. “Several characterizations, including cross-sectional SEM, X-ray diffraction and steady-state photoluminescence, confirmed this superior protection effect.”
The academics then integrated the top perovskite cell with a silicon bottom cell in a tandem device that achieved an efficiency of 30.04%. This cell was also able to maintain approximately 80% of its initial efficiency after 423 hours of continuous light. They claim the cell is one of the best performing 4T perovskite-Si tandem solar cells to date.
The description of the device is available in the study “Indium oxide buffer layer for perovskite/Si 4-terminal tandem solar cells with an efficiency of more than 30%”, published in the Journal of Energy Chemistry.
“Our work expands the limited selection of available SBL materials for pin-structured ST-PSCs and introduced a low-cost deposition approach for industrial applications,” Can concluded. “This work demonstrates significant potential for accelerating the commercialization and widespread deployment of perovskite solar photovoltaics.”
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