Owing to the growing importance of quantum dots in future materials and devices, this thesis mainly concerns with the synthesis, characterization and applications of quantum dots in conducting polymer composites and devices such as Schottky diodes and quantum dot sensitized solar cells (QDSSCs). Quantum dots (QDs) involved in these studies include II-VI semiconductors cadmium selenide (CdSe) and cadmium sulfide (CdS) and IV-VI semiconductor lead sulfide (PbS). As regards the work related to application of QDs in functional materials, CdSeQDs have been synthesized, characterized and incorporated in polyaniline (PANI). CdSe/PANI nanocomposites have been prepared with varying amounts of CdSe QDs in PANI by in-situ polymerization technique. Pure PANI, CdSeQDs and their composites have been characterized by using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and UV-VIS absorption spectroscopy. The surface morphologies have been investigated by Scanning Electron Microscopy (SEM). The electrical and dielectric properties have been studied by using 4-probe mechanism and LCR meter respectively. The DC conductivity of the nanocomposites has been studied in the temperature range from 298 to 368 K and it is increased with the temperature risedepicting the semiconducting behavior of the samples. DC conductivity is found to follow Mott’s 1D (one dimension) variable range hopping model. It is observed that AC conductivity of the samples is enhanced with the increase in temperature and the frequency dependent AC conductivity follows the universal power law. Dielectric behavior of the nanocomposites discussed as a function of frequency and temperature exhibits a rapid fall of dielectric constant with rise in frequencywhich can be described by Maxwell-Wagner capacitor model. It is observed that the dielectric constant is increased with the increasing temperature and also with the increase of QDconcentration in the nanocomposites. Two Schottky devices have also been fabricatedto study the device application ofCdSe/PANI nanocomposites. One device was fabricated employing layer-by-layer deposition of PANI and CdSe films on PEDOT-PSS/ITOcoated glass substrate {ITO (indium tin oxide)/PEDOT-PSS [poly (ethylene dioxy thiophene) poly (styrene sulphonate)]/PANI (polyaniline)/CdSe (cadmium selenide)} and the other by depositing PANI-CdSeQDs composite film on the same substrate (ITO/PEDOT-PSS/CdSe-PANI) using spin coating technique. The diode performance parameters have been compared and J-V characteristics of these devices show a rectifying contact with aluminum metal, however, with variation in performance parameters like barrier height, ideality factor and reverse saturation current density, the ITO/PEDOT-PSS/CdSe-PANI/Al (composite assembly) device exhibits better diode performance as compared to ITO/PEDOT-PSS/PANI/CdSe/Al (layer-by-layer) device.This work has been presented in Chapter 5 of this thesis. Fabrication and study of two series of low cost QDSSC devices prepared by varying successive ionic layer adsorption and reaction (SILAR) cycles: ITO/TiO2/CdS/CdSe/ZnS QDSSCs and FTO/TiO2/PbS/CdS/CdSe/ZnS QDSSCsare reported in Chapter 6 of this thesis.The structural, optical, morphological and electrical properties of these devices have been studied. Different modes of vibrations in the deposited films have been studied by RAMAN spectroscopy. X-ray Diffraction (XRD) patterns show that the particle size of the QDs increases with the number of SILAR cycles. However, the intensity peak of CdS QDs has not been observed after three SILAR cycles. UV-VIS spectroscopy measurement of the devices show enhancement in absorbance upto three SILAR cycles and saturation for further SILAR cycles. The SEM images of devices reveal capping of CdS QDs by CdSe QDs for four and higher SILAR cycles, resulting decrease in power conversion efficiency (PCE) of these devices. The J-V characteristics show that in order to achieve the best performance of QDSSC, the optimum parameters for CdS and CdSe QDs deposition are three cycles. The highest PCE of 5.0 % has been achieved after an optimization of dipping SILAR cycles. After adding 3 SILAR cycles of PbS QDs, the PCE value has been improved upto 6.43 %. Electrochemical Impedance Spectroscopy has been performed under dark conditions in order to discuss the physical mechanism of QDSSCs. Maximum values of recombination resistance (Rrec) and constant phase element (CPE) have been found for efficient devices with three SILAR cycles: ITO/TiO2/3CdS/3CdSe/3ZnS and FTO/TiO2/3PbS/3CdS/3CdSe/3ZnS QDSSCs. Lower and higher numbers of SILAR cyclesgive lower values of Rrec and CPE in all other QDSSCs. This shows that the charge carriers in QDSSCs with three SILAR cycles can be efficiently transported because of longer carrier lifetimes in these devices.