It has been reported that ITO/nc-TiO2/P3HT:PCBM/Ag inverted solar cells under air mass 1.5 global (AM 1.5G) illumination have a low efficiency of 0.13% [11]. The main reason may be due to the low efficiency of charge collection at the Selleck Vistusertib interface NVP-BSK805 in vitro between the active layer (P3HT:PCBM)

and top metal electrodes. One of the main strategies usually employed to overcome this problem is to insert interfacial layer materials such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) [17], MoO3[19, 20], WO3[11], and V2O5[21] between the active layer and anode (i.e., Ag electrode) to suppress the electron–hole recombination at the active layer/anode interface (i.e., P3HT:PCBM/Ag interface). In this research, from another point of view, a new strategy is put forward to reduce the electron–hole recombination at the active layer/cathode interface (i.e., TiO2/P3HT:PCBM interface) by depositing CdS quantum dots (QDs) on a nanocrystalline TiO2 (nc-TiO2) film by chemical bath deposition (CBD) to enhance the efficiency of the ITO/nc-TiO2/P3HT:PCBM/PEDOT:PSS/Ag inverted solar cell without CdS QDs. The CBD method has been successfully used to deposit QDs onto the photoelectrodes to increase the light absorption Wnt inhibitor in QD-sensitized solar cells [22]. However, this method is rarely used in organic BHJ PV cells. In this study,

to improve the power conversion efficiency of the solar cells, the deposited CdS QDs on the nc-TiO2 film were used to increase the UV-visible (UV–vis) absorption of the cells and the interfacial area between the electron donor and electron acceptor. Moreover, CdS, an n-type semiconductor, can serve as an electron-selective layer to reduce the recombination between photogenerated electrons and holes. In order to show more clearly the influence of CdS QDs on the performance of the ITO/nc-TiO2/CdS/P3HT:PCBM/Ag solar cell, the commonly inserted interfacial layer materials such as PEDOT:PSS between the P3HT:PCBM layer and Ag electrode are not used initially. The device architecture is shown schematically in Figure 1a, and the energy level diagrams of different

materials used in the device fabrication are shown in Figure 1b. Then, to further improve the efficiency, the PEDOT:PSS as a hole-selective during layer material is used in the ITO/nc-TiO2/CdS/P3HT:PCBM/PEDOT:PSS/Ag solar cell. Figure 1 Schematic diagram (a) and energy diagram (b) of the ITO/nc-TiO 2 /CdS/P3HT:PCBM/Ag device. Our results show that the performance parameters, such as the short-circuit current density (I sc), the fill factor (FF), and the open-circuit photovoltage (V oc), of the cells with CdS increased largely compared to those of the cells without CdS QDs. As a result, the efficiency of ITO/nc-TiO2/CdS/P3HT:PCBM/PEDOT:PSS/Ag inverted solar cells increased to 3.37% from the efficiency of 2.98% of the ITO/nc-TiO2/P3HT:PCBM/Ag solar cell.