Toshiba reports 8.4% efficiency for transparent Cu2O solar cell
Toshiba Corp (TYO:6502) has achieved a power conversion efficiency (PCE) of 8.4% for a transparent cuprous oxide (Cu2O) solar cell and continues work with a goal to reach 10% efficiency and 80% transmittance.
The company said today this is the highest PCE reported so far for a Cu2O cell. It estimates that a Cu2O-Si tandem cell using this Cu2O cell on top of a silicon cell could reach an efficiency of 27.4%.
The latest efficiency result has been achieved thanks to the more precise control of CuO and Cu impurities, the main reason for diminished PCE and transparency. These impurities are generated in the current reactive sputtering deposition method due to the nature of the Cu2O.
“X-ray diffraction analysis allows us to detect and quantify the degree of the CuO and Cu, giving us data that helps us to identify the best deposition method to control the impurities to the lowest level,” Kazushige Yamamoto, Fellow at Toshiba's Corporate Research & Development Center, commented.
The Japanese company developed the first transparent Cu2O solar cell in 2019, and presented a Cu2O-Si tandem cell with a PCE of 23.8% the same year. Other tandem cells being developed globally are approaching efficiencies of close to 30%, but they use highly expensive materials like gallium arsenide. Toshiba’s Cu2O cells are made using naturally abundant materials, which translates into lower costs.
Work towards 10% efficiency continues with support from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. Toshiba is also partnering with Toshiba Energy Systems & Solutions Corp to build Cu2O cells the same size as mass-produced silicon solar cells. The two firms aim to supply samples for external evaluations by fiscal 2023 with a roadmap to completing manufacturing technologies for commercial products by fiscal 2025.
One specific application of the high efficiency cells being analysed by Toshiba is in electric vehicles (EVs). Under the test criteria defined by NEDO, Toshiba estimates that the Cu2O-Si tandem cell could carry an EV 35 km without any need of recharging.