Enhance the light-harvesting capability of the ITO-free inverted small molecule solar cell by ZnO nanorods

The ITO-free inverted SMPV1:PCsub71/subBM solar cells with an Al doped ZnO (AZO) transparent electrodes are fabricated. The AZO thin film prepared by pulsed laser deposition (PLD) technique exhibits high transmission (85%) and low sheet resistance (~30 Ω/sq) and the power conversion efficiency (PCE) of devices based on AZO electrode can reach around 4%. To further enhance the light harvesting of the absorption layer of solar cells, ZnO nanorods interlayer is grown on the AZO layer before the deposition the active layer. The absorption spectrums of devices under various conditions are also simulated by RCWA method to identify the optical saturation length of the ZnO nanorods. The PCE of ITO-free inverted small molecule solar cell improved with ZnO nanorods can reach 6.6%.