Quantum Dots Interface Modification&Sensitization And Their Photovoltaic Characteristic

Quantum Dots sensitized solar cells have be considered as one of the advancedresearch topics in the field of solar cells, since its’ tunable spectral response range, highextinction coefficient and higher theoretical conversion efficiency. This dissertationtargeted at several main scientific issues in the field of quantum dots in sensitized solarcells, and launched a series of studies on PbS quantum dots interface modification ofphotoanode, new photocatalytic synthesis of PbS quantum dots, electron injection andphotovoltaic characteristic of core-shell quantum dots. The main results and conclusionsof this dissertation are as follows:（1） PbS quantum dots synthesized by in-situ method were used for interfacemodification of TiO₂photoanode. The photovoltaic characteristic results indicated thatthe PbS quantum dots with3prepar-circles showed the photoelectric conversionefficiency improved21%. According to the results of transient photovoltage spectra,dark current measurement and surface photovoltage spectroscopy, after PbS quantumdots interface modification, the traps on surface of TiO₂, known as “surface states”, wasextremely reduced due to the presence of PbS, therefore the charge recombination wasretarded significantly. And then structure and morphology of the PbS quantum dotswere studied by X-ray diffraction （XRD） analysis, BET physisorption andhigh-resolution transmission electron microscope （HR-TEM）. The results showed that2-3nm PbS quantum dots particles formed the major part of the particles. The certaindistribution of the particles sizes is benefit for filling the surface states of TiO₂films.（2） Since the currently synthesis methods of quantum dots shows problems such asrelatively low adsorption, nonuniformity size distribution and lots of toxic waste. PbSquantum dots were synthesized by an in-situ photocatalysis method using thephotocatalytic activity of nanocrystalline TiO₂films. The synthesis kinetics and reactionmechanism was discussed. The effective mass approximation calculation showed thatsize of the synthetic quantum dots is about1.7nm under1.8mW/cm²UV illuminationfor10minutes. The PbS quantum dots achieved showed good sensitization ability, andin the meantime this method is much more simple and environmentally friendly.（3） The electron injection and recombination and the relative photovoltaic characteristic for shell-thickness dependent CdSe/ZnS core-shell quantum was studied.The study results suggested that both the injection and recombination rate slow downwith the increasing of shell-thickness, until the thickness reached2molecular layers,when the decay rate begin remain a certain value. The corresponding quantum dotssensitized solar cells showed better photoelectric conversion efficiency and stability atthe same shell thickness.