Roughness effect on heterojunction photovoltaics

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Abstract
In this work, we present an investigation of the junction interface roughness effect on the open circuit voltage, V oc for thin filmheterojunctionphotovoltaics. The roughness effect is studied for self‐affine rough interfaces, which are described in Fourier space by the correlation model ∼σ2ξ2(1+aq 2ξ2)−1−H . σ, ξ, and H denote, respectively, the rms roughness, the in‐plane roughness correlation length, and the interface irregularity exponent (0<H<1). The roughness effect becomes significant for small H (<0.5), and for large long‐wavelength roughness of typical values σ/ξ∼0.1. The junction interface roughness may yield a contribution to V oc even up to 10%. Comparison of the results is performed with predictions in real heterojunctions, e.g., Cu x S/(Zn)CdS.