Nevertheless, the observed photocurrent density for the cell with Cu2S as CE is comparable with the published result of 3.06 mA/cm2[24]. In general, CdS QDSSCs

exhibit low fill factors (less than 40%) with any of the tested CE materials. Figure 1 J-V curves of CdS-based QDSSCs with various CEs. Table 1 Performance parameters of CdS QDSSCs with various CEs   J SC (mA/cm2) V OC (V) FF (%) η (%) Pt 6.09 0.460 38 1.06 Graphite 6.89 0.485 36 1.20 Carbon soot 6.62 0.515 34 1.16 Cu2S 3.70 0.280 28 0.29 RGO 3.35 0.380 29 0.37 In the study of CdSe QDSSCs, J-V curves of each solar cell combination with different CE materials are shown in Figure 2, and the corresponding performance data are summarized in Table 2. Unlike the CdS QDSSC, the CdSe QDSSC exhibits high efficiencies with Hydroxychloroquine order Cu2S and platinum as CE materials. Among these results, the best performance is observed in solar cell assembly with commercial platinum catalyst as the CE. The CdSe QDSSC with platinum as the CE produced an efficiency of 1.41% followed by 1.16% with Cu2S as the CE. The fill factor and V OC with Cu2S are also good. These results show that Cu2S is compatible with CdSe QD as a CE material. On the other hand, carbon-based materials like graphite and carbon soot which work well in the NVP-BKM120 CdS QDSSC perform

poorly when coupled with CdSe QD-sensitized TiO2 electrodes. The poor performance from these materials could be attributed to the low electrocatalytic activity at the CE/electrolyte interface against the fast electron injection and transfer from CdSe QDs into the photoanode substrate. The preference of different CE materials for CdS and CdSe QD-sensitized TiO2 electrodes

could be explained by electrochemical MTMR9 impedance spectroscopy (EIS) study. The observed performance of our QDSSC is rather low when compared with result from other groups. However, we anticipate the performance to be better if optimization of the photoanode is carried out such as addition of a scattering layer and passivation with a ZnS layer. Figure 2 J-V curves of CdSe QDSSCs with various CEs. Table 2 CdSe QDSSC performance parameters with various CEs   J SC (mA/cm2) V OC (V) FF (%) η (%) Pt 6.80 0.470 44 1.41 Graphite 5.53 0.415 22 0.50 Carbon soot 1.58 0.310 15 0.07 Cu2S 6.01 0.430 45 1.16 RGO 5.15 0.415 31 0.66 EIS is performed to understand the kinetic processes within the QDSSC. Typically, an EIS spectrum for a dye-sensitized solar cell (DSSC) consists of three semicircles in the Nyquist plot [25]. This characteristic is also applicable to QDSSC [24]. The three semicircles correspond to the response in high-frequency, intermediate-frequency and low-frequency regions when the cell is biased at its open-circuit potential.