Performance enhancement of polymer solar cells with high work function CuS modified ITO as anodes

In this paper, a thin layer of high work function CuS was introduced to the interface between the anode and hole transporting layer (HTL) to modify the indium tin oxide (ITO) anode. Modified ITO substrates possess a higher work function, a lower sheet resistance and a negligible loss in transparency. More importantly, a thin layer of CuS can also benefit for the hole transporting of the device. Polymer solar cells (PSCs) utilizing modified ITO anodes exhibit a significant enhancement in power conversion efficiency ( PCE ) and air stability compared to devices with normal ITO anodes. This anode modification strategy applies to different active layer systems. Anode-modified devices with poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) as the active layer exhibit a PCE of 3.5%, while poly(4,8-bis(5-(2-ethyl-hexyl)-thiophene-2-yl)-benzo[l,2-b:4,5-b′] dithiophene-alt-alkylcarbonyl-thieno[3,4-b]thiophene) (PBDTTT-C-T) and [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM) system shows a PCE of 7.4%. As a result, this work provides a good compatibility for modification of ITO by a thin layer of CuS in PSCs to achieve better performance.