In this work,a layer of PbS was anchored on TiO2 and CdS layers were deposited stepwise on PbS and the solar cell performance was investigated with respect to PbS and CdS layer thicknesses and their surface passivation properties were investigated.
Cross section SEM image and EDX analysis of TiO2/1PbS/3CdS/2ZnS photoanode is shown in Fig. S1 and the surface SEM images of TiO2/1PbS, TiO2/3CdS, TiO2/1PbS/3CdS/2ZnS, and higher magnification of TiO2/1PbS/3CdS/2ZnS are shown in Fig. S2a–d respectively. Previous work carried out on PbS/CdS type of quantum dots with the ethanedithiol treatment reported 4.65% efficiency with aqueous polysulfide electrolyte [9]. In this investigation,TiO2 photoanode was pre-adsorbed in 3-mercaptopropionic acid sodium sulfide precursor solution and the pre-adsorption step facilitates deposition of more quantum dots and good connection between TiO2 and quantum dots,resulting in enhance solar cell performance. Fig. 1 shows the I–V characteristics of solar cells fabricated with PbS/CdS photoanode with the variation of number of PbS and CdS cycles and the measured solar cell performances are given in Table 1. The solar cell performance of the optimized structure were repeated for four times and the measured solar cell performances are given in TableS 3.