Progress in Photovoltaics | Volume33, Issue 1 EU PVSEC 2023 | January 2025 | Pages 100-108
Patrick Schygulla, Ralph Müller, Oliver Höhn, Michael Schachtner, David Chojniak, Andrea Cordaro, Stefan Tabernig, Benedikt Bläsi, Albert Polman, Gerald Siefer, David Lackner, Frank Dimroth
To increase the efficiency of silicon solar cells above 30 %, the introduction of additional absorber layers is necessary. Semiconductor materials with higher band gaps can utilise the short-wavelength part of the solar spectrum more efficiently so that less energy is lost as heat.
In this article, we have presented a triple-junction solar cell whose efficiency of 36.1 % under the AM1.5g standard spectrum is currently the highest of all silicon-based solar cells. We used a thin top cell layer stack of III-V compound semiconductors, i.e. elements such as gallium, indium, arsenic and phosphorus, which we bonded directly to a silicon sub-cell after crystal growth. However, this only increased the overall thickness of the cell by around 1 %.
A photonic lattice structure on the back, developed and implemented jointly with the Dutch research institute AMOLF in a successful international cooperation, led to an increased light absorptance in the silicon sub-cell. We also succeeded in improving the material quality of the III-V sub-cells so that the voltage of the solar cell increased by 60 mV compared to previous generations. Both measures together made the new record possible. Furthermore, we established a new measuring technology to analyse the light coupling between the individual sub-cells of the solar cell. Thereby we show how we can achieve even higher values in future by adjusting the layer thicknesses.