5810.1:
Optical nano gratings for nano crystalline silicon solar cell
Abstract
Considerable progress has been achieved so far in solar cell research in terms of device design and material quality. One of the most important invention is the micromorph tandem solar cell, combining a layer made of nano silicon crystals, with an amorphous silicon layer (mc-Si/a-Si:H). In addition, with the aim to decrease the cost of the solar cell, plastic substrates have already been successfully employed. However, a serious gap remains with respect to optically transparent electrical contacts and back-reflectors. These two layers (front contact and back-reflector) have now become a crucial issue for further improving the conversion efficiency of thin film silicon solar cells : the more photons that can be absorbed in the solar cell, the more the conversion efficiency can be increased. The front contact has to be optimized with respect to wide-spectrum anti-reflection coating, whereas the back-reflector has to optimally scatter the near-infrared light. Nano structured gratings or nano-structured plastic (polyimide and PET) substrates are promising methods to improves the conversion efficiencies of micromorph tandem and amorphous solar cells while maintaining cell manufacturing cost as low as possible. This study should allow us to determine which of the methods is the most suitable: nano-texturing by a diffraction nano-grating or a random nano-texturation obtained by plasma treatment.