Optical properties and dynamic process in Cd1−xMnxSe quantum dots sensitized solar cells

Overall, the quantum dots sensitized solar cells were successfully prepared with the enhanced short current density from 7.7 mA/cm2 to 19 mA/cm2 based on Mn2+ ions doped on CdSe nanocrystal by successive ionic layer absorption and reaction. There were rapid effects of Mn2+ ions on optical, physical, chemical, and photovoltaic properties of the quantum dots sensitized solar cells. Consequently, the highest efficiency of the quantum dots sensitized solar cells increased dramatically from 1.7% for pure CdSe nanocrystal to 3.8% for Mn2+ ions doped on pure CdSe nanocrystal. Actually, the Mn2+ dopant rise in the conduction band of pure CdSe nanocrystal, reduces recombination, enhances the efficiency of high harvesting, and improves the charge transfer and collection. In addition, the optical properties, the direct optical energy gap, and both conduction band and valence band levels of the compositional CdS, Cd1−xMnxSe were estimated by Tauc model and discussed in details. This Tauc model is useful for us to understand the alignment energy structure of the compositions in electrodes, in particular, the conduction band and valence band levels of CdS, Cd1−xMnxSe nanoparticles. As a result, a rise or a drop of the conduction band and valence band levels when Mn2+ content was changed. Correspondingly, the Electrochemical Impedance Spectra were carried to determine dynamic resistances in QDSSCs.