In this study, bandgap engineering was utilized to assess the efficiency of photoanodes incorporating CdS nanocrystals and AgInSe2 (AISe) quantum dots (QDs) in quantum dot-sensitized solar cells (QDSSCs). Initially, the deposition of CdS(Xc) nanocrystal layers on a TiO2 substrate was tested using the SILAR method with varying cycles (X = 1–6). Optical transmission analysis revealed a redshift in the absorption edge and reduced transmission with an increasing number of cycles. J-V analysis of TiO2 NCs/CdS(Xc) photoanodes identified cycle X =5 as optimal. The short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and maximum power conversion efficiency (PCE) were 15.5 mA/cm2, 614 mV, 40 %, and 3.76 %, respectively. Subsequently, pre-synthesized AISe QDs were deposited on TiO2 nanocrystals/CdS(Xc) photoanodes, exhibiting a single absorption edge with a bandgap energy of 2.19 eV for all photoanodes. The TiO2 NCs/CdS(5c)/AISe/ZnS photoanode showed an increase in Jsc and efficiency, reaching 17.25 mA/cm2 and 4.27 %, respectively. Utilizing submicron-sized TiO2 hollow spheres (HSs) as a light-scattering layer further enhanced light absorption and performance. It was demonstrated that this approach increased the photovoltaic parameters to a Jsc of 19.12 mA/cm2, FF of 43 %, and an overall efficiency of 4.75 %.
