The approach of increasing incident photon absorption and decreasing charge recombination in solar cells by regulating the bandgap energies of the CdSe0.3S0.7/CdSe photosensitizer layer

CdSe0.3S0.7/CdSe quantum dot sensitized solar cells are a desirable choice for increasing photovoltaic efficiency due to their high light-harvesting efficiency. In this study, the CdSe0.3S0.7 chalcogenide quantum dots were adsorbed onto the TiO2 NPs mesoporous film using the successive ionic layer adsorption and reaction (SILAR) method with variation cycles ranging from 1 to 7. when the thickness of the CdSe0.3S0.7 quantum dots is modified, the quantum dot sensitized solar cell with TiO2 NPs/CdSe0.3S0.7(5c)/ZnS photoanode shows higher short circuit current density (JSC), open circuit voltage (VOC) and power conversion efficiency (PCE) values of 17.80 mA/cm2, 530 mV and 3.25 %, respectively. The corresponding photoelectrode according to the results of Surface morphology analyses is still suitable for loading other quantum dots, because there are still large pores on the surface. The CdSe QDs were loaded using the Chemical Bath Deposition (CBD) technique at various times from 6 to 15 min' coverage of TiO2 NPs/CdSe0.3S0.7 photoanode. The optimal thickness of the CdSe layer causes its energy levels to be aligned with the other layers and allowing photogenerated carriers to move between bands with a strong driving force before recombination. The cell with the TiO2NPs/CdSe0.3S0.7(5 cycles)/CdSe(12min)/ZnS photoelectrode has the highest JSC, VOC and PCE values of 24.70 mA/cm2, 580 mV and 6.25 %, respectively. The efficiency increased by 92 % compared to the reference cell, which only included CdSe0.3S0.7 QDs, and the IPCE and APCE curves had higher intensities and spanned a wider range of visible wavelengths. These changes are the result of enhanced light harvesting efficiency. J-V characteristics of the QDSCs with TiO2NPS/CdSe0.3S0.7 (5c)/CdSe (Ymin)/ZnS, Y = 6–15 min, photoanodes (a) and corresponding flat band energy diagram of the co-sensitized TiO2NPS/CdSe0.3S0.7 (5c)/CdSe (12min) photoelectrode (b). [Display omitted] •Fabrication of high efficiency CdSe0.3S0.7 and CdSe quantum dots sensitized solar cells by tailoring the bandgap energies of sensitizing layers.•Solar cells based on the TiO2NPs/CdSe0.3S0.7./CdSe new photoanodes have a broader light harvesting efficiency over 500 nm compared to cells without the CdSe co-sensitizer layer.•The CdSe layer improved the APCE and IPCE curves by widening the response wavelength area with a high intensity of nearly 80 %.•The CdSe co-sensitizer layer's ability to effectively increase the power conversion efficiency by