Download or read book Optical Characterization of Nanomaterials and Study of Photoinduced Electron Transfer in Quantum Dot Sensitized Solar Cells written by Baichhabi Raj Yakami and published by . This book was released on 2017 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: The potential of environmentally friendly solar energy is enormous, but the fabrication of solar cells that are efficient and competitive to other sources of energy remains a serious challenge. The quantum dot sensitized solar cells (QDSSC) is an encouraging cost-effective option to study as it has the potential to overcome the maximum theoretical limit of traditional solar cells. The key components in QDSSCs is the quantum dot/photoanode heterostructure. So, the study of optical properties of quantum dots and photoanode materials, and the charge transfer at the interface is necessary to understand and improve the efficiency and durability of these solar cells. Zinc Tin Oxide (ZTO) has potential for use as a photoanode in QDSSCs. So, the optical properties of ZTO nanowires was studied by using diffuse reflectance, Photoluminescence(PL), and Time Resolved PL (TRPL) measurements. The ZTO nanowires have a direct forbidden transition and thus do not have band to band PL. The two distinct PL peaks observed are centered at 1.86eV (red) and 2.81eV (blue), representing two distinct defect state transitions. The time resolved PL measurements show complex non-exponential decays at all wavelengths, indicative of defect to defect transitions, with the red emissive states decaying much slower than the blue emissive states. We propose an energy band model for the nanowires and the associated transitions between the defect states that are consistent with our measurements. One of the goal of this dissertation is to study the effect of Mn doping on ZTO and the electron transfer from CdSe QDs to Mn ZTO nanoparticles. We have successfully synthesized high surface area & single phase ZTO and Mn doped ZTO NPs using hydrothermal synthesis method. The incorporation of Mn into the ZTO has been studied by using XRD, TEM and XPS. We find that the Mn2+ ion most likely substitutes for the Zn2+ ion in the ZTO crystal. The Mn doping not only changes the magnetic properties, but also modifies the optical properties of ZTO nanoparticles. It modifies the band gap energy, changes the band tail states, and creates mid-band gap states as depicted in absorbance spectra. In addition, the Mn doping in ZTO quenches the defect PL in the ZTO nanoparticles. Finally, we sensitized ZTO and Mn ZTO nanoparticles films with CdSe quantum dots to form CdSe/ZTO and CdSe/Mn ZTO nanoparticle interfaces. A comparative electron transfer study is conducted in CdSe/Mn ZTO and CdSe/ZTO interface using fs transient absorption. Our result suggests that the electron transfer from CdSe is a not a single step process, but instead involves the intermediate charge transfer state. The faster time constant is associated with charge transfer and is found to be 2 ps and 3.7 ps in CdSe/ZTO and CdSe/Mn ZTO samples, respectively. The slower time constant is due to charge dissociation and occurs on a time scale of 28 ps and 30 ps in CdSe/ZTO and CdSe/Mn ZTO, respectively. The observed electron transfers differences due to the Mn doping in the ZTO nanoparticles has been analyzed using the Marcus theory of electron transfer, considering the effect of driving force and sub band gap states on the transfer rate, and agrees with our measurements.