مشخصات پژوهش

The principal aim behind doping of cadmium sulfide (CdS) quantum dots (QDs) by gadolinium (Gd) cations and fabrication of core (CdS)-shell (cadmium selenide (CdSe)) nanostructures was to increase the performance in the QD-sensitized solar cells (QDSSCs). By simultaneously doping with Gd and designing the core–shell nanostructures, the well-acted photovoltaic cells were fabricated where short current density (Jsc) = 14.91 mA/cm2, fill factor (FF) = 64.9%, open-circuit voltage (Voc) = 707 mV, and power conversion efficiency (η) = 6.84%. The addition of zinc sulfide (ZnS) layer onto TiO2/Gd-doped CdS@CdSe photoanodes improved the cell parameters including Jsc, FF, Voc, and η up to 16.34 mA/cm2, 65.24%, 710 mV, and 7.57%, respectively. The presence of Gd3+ in the the CdS crystal lattice promotes the charge injection rate from the conduction band (CB) of CdS to CB of TiO2 by successive trapping and losing the photoinduced electrons due to its unique half-filled electron configuration in valance f orbitals. Upon creating the Gd3+ doped-CdS@CdSe structures, the exciplex states were formed to reduce the effective bandgap of QDs and expand the light-harvesting range in visible wavelengths. The comparison of relative chemical capacitance (Cμ) under both dark and illumination conditions, obtained from electrochemical impedance spectroscopy (EIS) measurements, revealed that the Gd3+ doping of QDs can shift the CB level of TiO2 and, thereby, elevate the Voc. Moreover, the EIS and photoluminescence (PL) spectroscopy showed that doping suppresses the charge recombination at the photoanode/electrolyte interfaces and also improves Jsc and η in the fabricated cells