Study of the device characteristics of a CdTe solar cell under weak light irradiance (E-irra) is important both for the understanding of the fundamental device physics and for the commercial application, where E-irra with intensity much less than one sun is often encountered for an outdoor solar cell module. In this study, CdTe solar cell performance under E-irra as low as 0.015 sun was studied. Both the fill factor (FF) and the open-circuit voltage (V-oc) were found to be critically affected by the shunt resistance at low E-irra. The current shunting depends critically on the physical location of the shunting paths in the CdTe absorber layer. Space-charge limited current (SCLC) was identified to be an important contribution to the shunting current in thin film CdTe solar cell. At an E-irra as low as 0.015 Sun, CdTe solar cell with a high shunt resistance maintained an efficiency of similar to 70 to 80% of the value tested at the standard AM1.5 E-irra. The experimental results showed that polycrystalline CdTe thin film solar cell is a good photovoltaic device for electric power generation at low E-irra. This study provides constructive guidelines for the future design and fabrication of CdTe solar cells. (C) 2015 Elsevier B.V. All rights reserved.