Toshiba has estimated that positioning the new Cu2O solar cell over a 25% PCE silicone cell realizes a Cu2O-Si tandem cell with a 28.5% PCE—notably surpassing 26.7%, the highest reported PCE for any standard silicon cell (*3), and close to 29.1%, the highest reported PCE for any GaAs cell.
Under test criteria defined by NEDO, Toshiba found that a one-time charge enables the current Cu2O-Si tandem cell to power an electric vehicle (EV) for 37km, and further improvements in solar cells toward the theoretical maximum efficiency of 42.3% are expected to extend the range to a distance approaching 55km. These are both recognized as practical distances for short trips without recharging, and would reduce charging frequency for longer trip.
Toshiba targets a practical Cu2O-Si tandem cell with a 10% PCE Cu2O cell and an overall PCE of 30%, and the new cell records solid progress to that goal. Looking to mass production, the company is working to enlarge cell size, and has made a prototype with a power generation area of 40mm2 and a PCE around 8% (Figure 6). The efficiency falloff in the larger cell is due to a less uniform layer and Toshiba continues to refine thin film deposition technology for uniform deposition over a larger area.