Photovoltaic Module Spectral Mismatch Losses Due to Cell-Level EQE Variation

Abstract

Understanding the impact of variation in the solar spectrum on photovoltaic (PV) device output is critical for accurate and reliable PV performance modeling. While previous studies have examined these spectral effects extensively at the module level, this study examines the spectral impact at the cell level and how subsequent current mismatch can influence module-level output. Cell-level external quantum efficiency (EQE) data from 11 new commercial PV modules are analyzed. The module power output, as determined by the spectral mismatch factor of the module-limiting cell, is computed using the measured cell EQE data in conjunction with gridded meteorological and spectral irradiance data simulated at an approximately 20 $\mathbf{\mathrm{km}}$ resolution across the contiguous USA over one year. This study finds only a small variation in annualized module output of around 0.2% as a result of intramodule EQE variation. However, these losses exhibit significant seasonality, varying by up to around four times the annualized energy difference on a month-to-month basis. The seasonality of the energy loss has implications for subannual PV performance analysis applications such as capacity testing.