23.5% efficient silicon solar cell with rear micro contacts of c-Si//spl mu/c-Si:H heterostructure

To obtain high efficiency silicon solar cells, we have investigated the rear heterostructure comprising a p-type single crystalline silicon (c-Si) substrate and a highly boron doped (p/sup +/) hydrogenated microcrystalline silicon (/spl mu/c-Si:H) film. This heterostructure was formed by rear micro contacts where a SiO/sub 2/ film was opened on the rear surface of the substrate. Voc was improved by an effective BSF using this heterostructure. With optimal design of finger electrode patterns, a conversion efficiency of 23.5% (AM1.5, 25/spl deg/C, 100 mW/cm/sup 2/) was obtained for a single crystalline silicon solar cell in 5/spl times/5 cm/sup 2/ area.