Efficiency of a solar cell with intermediate energy levels: An example study on hydrogen implanted Si solar cells

摘要

For any pn junction solar cell, there is a theoretical limit to its conversion efficiency, which is determined by its band gap. This efficiency may exceed the limit by introducing an intermediate level (IL) that can facilitate the sub-band-gap optical absorption, but the IL can simultaneously enhance the carrier recombination rate. To understand the net effects of the IL, it is necessary to estimate the rates of both the optical absorption and carrier capture via the IL. In this study, trap parameters and the optical absorption coefficient are evaluated for defect levels in hydrogen implanted silicon wafers using deep level transient spectroscopy, the optical-capacitance transient spectroscopy, and carrier lifetime measurements. Using the obtained trap parameters, the characteristics of hydrogen implanted silicon solar cells are simulated. The simulation results indicate that it is not possible to realize improvements in efficiency by performing hydrogen implantation.