Synthesis of semiconductor quantum dots study of their optical properties and their application in sensitized solar cells

Abstract

Requirement of clean and cheap renewable energy production by understanding and thenmanipulating the physics of semiconductor nanostructures to realize cost effective and efficientNanophotovoltaic devices is the primary drive for the current research Many advantages ofsemiconductor quantum dots QDs like higher optical absorption cross section wavelengthtunability reduced phonon mediated relaxation and capability for solution processing at a lowcost made these very popular Here we have reported easy economic synthesis and fabricationprocedures for QD based nano photovoltaic devices The main focus of this thesis work is to develop synthesis procedures with reducedsynthesis steps while maintaining optimum optical and electronic transport qualities of thesenanostructured devices We have developed a simple low temperature and aqueous synthesismethod for CdTe QDs The measured photoluminescence quantum yield of the as prepared QDsis highest among the aqueous based synthesis procedures reported till now for CdTe QDs Wehave used these QDs as photo absorber in Quantum Dot Sensitized Solar Cells However it wasevident that the polysulfide electrolyte reacts with these CdTe QDs which reduces theperformance of QD sensitized cells Further we have tried to avoid such reactive degradationusing type II heterostructure i e core shell structure with CdTe as core and CdSe as shell We then presented a quicker economic and less toxic single step aqueous synthesisprocedure for core shell QDs at relatively low temperature We have shown that the structural aswell as optical properties of these core shell QDs are almost similar to that of core shell QDssynthesized with purification of core QDs We have demonstrated that the power conversionefficiency of QD sensitized cells depend on their shell thickness Reasonable good efficiency 2 is measured for the devices fabricated using core shell QDs hav newline newline