Thin film poly-Si solar cell, with “star structure” on glass substrate fabricated at low temperature

The performances of thin film poly-Si solar cells with a thickness of less than 5 μm on a glass substrate have been systematically investigated as a function of thickness. The cell of glass/back reflector/n-i-p poly-Si/ITO is well characterized by the structure of naturally surface texture and enhanced absorption with a back reflector (STAR), where the active i layer was fabricated by plasma chemical vapor deposition (CVD) at low temperature. The cell with a thickness of 3.5 μm and 2.5 μm demonstrated an intrinsic efficiency of 9.8%, as independently confirmed by Japan Quality Assurance. The optical confinement effect explains the excellent spectral response at long wavelength for our cells through the PC1D analysis. The higher sensitivity at long-wavelength of our cell which appeared in quantum efficiency curves is well correlated to the result of reflectance measurement. The open circuit voltage of 0.526 mV and the efficiency of 9.3% has been achieved for the cell with a thickness of 1.5 μm, which was proved to be entirely stable with respect to the light-soaking. The stabilized efficiency of our developed a-Si:H/poly-Si/poly-Si stacked solar cell is 11.5%