Single crystalline cesium doped ZnO nanorods with homogeneous size and shape were grown hydrothermally on ITO substrates that are presented in our previous work. According to the previous work, XRD analysis showed that cesium doped ZnO nanorods are wurtzite single crystals and are grown preferentially along the c-axis. Also, the electrical conductivity of doped ZnO showed higher values for the 1% cesium, which confirmed incorporation of the cesium dopant. Cesium doped ZnO nanorods are suitable candidates for applications in solar cells. So, in this research, we employed cesium doped ZnO nanorods with the different dopant concentration in inverted polymer solar cell. By comparing the effect of doped ZnO nanorods with diverse dopant concentration (0, 0.5, 1.0, 1.5 and 2%) on the performance of devices, 1.0% cesium doped ZnO was found as the most effective doping level among the selected doping concentrations. Also, using 1.0% cesium doped ZnO nanorods, Jsc of 8.21 mA/cm², Voc of 0.541V and Fill Factor of 63.01% were achieved, which led to power conversion efficiency of 2.80%.