Record-Breaking Tandem Solar Cell Achieves 29.9% Efficiency

• Experience the breakthrough of thin-film tandem solar cells: Researchers at Empa, NUS and HI ERN achieve record efficiency of 29.9%, lower electricity costs & 2000 Wh/m2 daily.

The researchers at Empa, National University of Singapore (NUS) and Helmholtz Institute Erlangen-Nürnberg for Renewable Energy HI ERN have developed commercially viable perovskite/CuInSe2 thin-film tandem solar cells with a record efficiency of 29.9%. To do this, they employed new electrical and optical techniques, such as methyldiammonium diiodide and adjusting the optical interference spectrum. This led to a 20.2% efficiency (21.8% by J-V scan) for the perovskite cell and 81.5% average near-infrared transmittance. Techno-economic studies also showed that these tandems could deliver nearly 2,000 Wh/m2 daily for certain locations and offer competitive electricity costs, ranging from 3 to 5 USDcents/kWh within ±30° latitude. Therefore, the team's work has demonstrated the commercial viability of thin-film-based tandems for large-scale deployment.

What Techniques Enabled the Record Efficiency for Perovskite/CuInSe2 Thin-Film Tandem Solar Cells?

• Deposition of the perovskite layer with a methyldiammonium diiodide (MAI) precursor
• Adjusting the optical interference spectrum of the two-component stack
• Modulation of the contact and back-reflector layers to optimize the current-voltage characterization
• Optimization of the interfacial layers to minimize shunts and light trapping
• Use of an all-oxide architecture and low-cost materials
• The use of an annealing step to increase the photovoltaic performance and stability
• Utilizing a high-performance selective emitter that enables a high open-circuit voltage and fill factor