Bifacial multicrystalline silicon thin film solar cells
in: Solar Energy Materials and Solar Cells (2017)
Based on well-defined lab conditions, we have developed experimental methods to characterize bifacial laser crystallized multicrystalline silicon (mc-Si) thin film solar cells fabricated on glass. Key parameters which determine the performance of the bifacial solar cells such as light intensity and incidence angle dependence on both sides have been characterized. From these parameters and from the local irradiance data, the annual power output of the bifacial solar cells can be simulated easily. This will provide the guide for the installation of the bifacial solar panels. In addition, bifacial measurements under well-defined conditions using a single sun simulator have been performed by means of a mirror. This method shows very promising results: Nearly 60% additional current can be obtained. The best bifacial mc-Si thin film solar cell shows a “bifacial efficiency” of 12.4% compared to state of the art monofacial mc-Si thin film counterpart of 12.1%. According to our simulation, even a “bifacial efficiency” above 14% is realistic if the solar cell is installed in front of a white diffuse scattering surface with a reflectance of ~90%. The threshold of additional light contribution at which the bifacial mc-Si thin film (without reflector) solar cells outperform the monofacial ones (with reflector at the rear side) have been determined by simulations. This shows that the advantages of the bifacial cells can already be observed at very low level (<25%) of additional reflected light contribution.