Comparison of experimental data with AMPS modeling of the effects of CdS layer thickness on the CdS/CdTe solar cell

Prevailing wisdom has it that the CdS layer is dead with respect to photogeneration of carriers, acting only as an optical filter. This assumption is examined by comparison of experimental spectral response data with that obtained by AMPS simulation. AMPS layer thickness (X_CdS) is small (∼0.1 μm), the layer could contribute several mA/cm² of photogenerated current. The high electric field present in the CdS strongly decreases recombination losses in the bulk CdS and at the TCO/CdS and CdS/CdTe interfaces. The CdS layers theoretical contribution also depends critically on the carrier density there and on the conduction band discontinuity at the TCO/CdS interface. Removing the CdS layer from the model entirely causes J_sc, V_oc and ff reductions, as observed experimentally, indicating that the effective recombination loss at the TCO/CdS Interface is much larger than that at the CdS/CdTe interface.