Identifying the Dominant Recombination Mechanism and Its Location in CdTe Solar Cells

CdTe-based solar cells have achieved power conversion efficiencies exceeding 23%, but the open-circuit voltage remains significantly below the theoretical limit, primarily due to high non-radiative recombination rates. The precise location of this recombination and a standardized method for identifying it, however, remain unclear. To address this, we applied a suite of steady-state and transient optoelectrical characterization techniques, along with simulations and rigorous data analysis, to investigate high-performance CdTe solar cells fabricated by First Solar, both with and without a back interface passivation layer designed to mitigate surface recombination. Our results show that first-order non-radiative recombination, particularly back surface recombination, dominates device performance, even under illumination intensities as high as 5 suns. We further quantified the effective surface recombination velocities as 1000 cm/s and 1364 cm/s for devices with and without the passivation layer, respectively. This study advances the understanding of recombination mechanisms in CdTe solar cells and provides a method to distinguish bulk from surface recombination.