First attempt to build lead-free perovskite-CIGS tandem solar cells

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Researchers led by a team at Visvesvaraya National Institute of Technology in India have simulated a tandem solar cell based on a lead-free halide perovskite top cell with a wide energy bandgap of 1.6 eV and a copper-indium-gallium-selenide (CIGS) bottom device with a narrow bandgap of 1.1 eV.

The novel two-terminal device has a potential conversion efficiency of 26.06%

“The current study focuses on minimizing the losses associated with single junction solar cells like thermalization and transmission losses by using a novel device structure consisting of perovskite (CsGeI3) and CIGS,” Sushama M. Giripunje, corresponding author of the research, told pv magazine, adding that it was a first attempt to pair a top cell based on CsGeI3 with a bottom CIGS cell in a tandem structure.

The scientists described how they used SCAPS 1D to simulate a novel tandem CsGeI3 perovskite-CIGS cell in “Numerical Simulation Analysis of Two-Terminal Monolithic Perovskite-CIGS Tandem Solar Cell for Enhanced Photovoltaic Performance Using SCAPS-1d,” published by Langmuir.

The group designed the tandem solar cell structure using a filtered spectrum approach.

To ensure the accuracy of the simulated results, the team first calibrated both the top and bottom solar cells using experimental data and then compared the simulated results with experimental findings.

They investigated the impact of thickness, parasitic resistance, temperature, quantum efficiency, band diagram, absorption coefficients, and two-diode model equivalent circuit parameters on solar cell performance.

They designed a CsGeI3/CIGS tandem solar cell with a 273 nm top cell, simulated under AM1.5G, and a 1000 nm bottom cell.

The SCAPS software predicted power conversion efficiencies were 16.93% and 16.49%, respectively. The tandem device conversion efficiency was 26.06% with an open-circuit voltage of 1.73 V, short-circuit current density of 19.32 mA cm−2, and a fill factor of 77.98%.

“This perovskite-CIGS tandem design demonstrates a promising route for developing high-efficiency, low-cost tandem solar cells,” said Giripunje.

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