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Shading on photovoltaic (PV) modules due to shadows, covering, dust, etc., usually characterized as semi-transparent, will significantly affect the power generation capacity. No systematic study has considered the impact of semi-transparent coverings on the power generation capacity of PV modules. This paper covers a single cell in the PV module using a covering with a transmittance of 18.55% and systematically investigates its impact on the power generation capacity. The open-circuit voltage (<i>V_oc</i>) of the PV module is nearly unaffected by semi-transparent coverings because the covered cell can be considered as working at a lower irradiance and thus can output a voltage close to that of the uncovered cell. The short-circuit current (<i>I_sc</i>) is significantly affected by coverings because it is co-contributed by the photocurrent (evaluated based on the covering ratio R and transmittance) and the reverse bias current Δ<i>I_sc</i> (the covered cell is in a reverse bias state). The Δ<i>I_sc</i> increases with <i>R</i> because more charge accumulates at the bi-ends of the covered cell; but, it decreases at full covering, which implies that in a partially covered case the uncovered part contributes more to Δ<i>I_sc</i> than the covered part. The fill factor (<i>FF</i>) of the PV module first increases and then decreases with <i>R</i>, as the equivalent resistance of the covered cell increases rapidly with <i>R</i>, which replaces the wire resistance in dominating the series resistance of the PV module when <i>R</i> > 0.6. This work is of great theoretical significance in analyzing the output characteristics of PV modules under real conditions.