High-Efficiency Large-Area Screen-Printed Solar Cell on Epitaxial Thin Active Layer With Porous Si Back Reflector Using Standard Industrial Process

Large area 17.3% high-efficiency screen-printed solar cells on a 90-μm-thick epitaxial silicon (epi-Si) active layer with a porous silicon (PSI) back reflector were fabricated using a 182-cm
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epitaxial wafer equivalent (EpiWE) structure and a standard industrial process. The PSI layer was studied and optimized to serve as an efficient back reflector in the finished device. An effective back surface recombination velocity (BSRV) and back internal reflectance (Rb) of 90 cm/s and 88%, respectively, were extracted by PC1D modeling of the EpiWE cell. These values of BSRV and Rb are superior to a standard industrial full Al-BSF Si solar cell, where BSRV and Rb are usually ≥200 cm/s and ~65%, respectively. Model calculations showed very little drop in cell efficiency if the thickness of active epi-Si layer is reduced to ~30 μm because of the good-light trapping provided by the optimized PSI back reflector.