List of Schemes

Abstract

Scheme 3.1. Schematic representation of electronic wave-flinction extending towards shell which results in the slow electron cooling observed for CdTe/ZnS NCs 98 Scheme 3.2. The formation of abrupt and smooth interfacial alloyed layer in CdTe/ZnSe core/shell NCs at different reaction temperature 113 Scheme 4.1. Plausible mechanism for CdSe/PbSe Janus HNC formation, (a-b) The CdSe NC reaches its maximum size in 2-5 minutes of growth after which Cd" to Pb" cation exchange starts to take place. The first layer of PbSe might form through ligand assisted cation exchange mechanism.'" (c-d) Following this the Cd~" to Pb"* exchange will proceed through vacancy assisted cation migration mechanism.''''" Once a Cd-vacancy forms at the surface, it will migrate to the CdSe/PbSe interface and is filled up by a Pb-atom. The Pb-vacancy diffuses to the surface recombining with Pb of a Pb-oleate molecule. This layer-by-layer replacement of CdSe continues until the reaction stops 130 Scheme 4.2. The quasi type-II alignment with epitaxy between two phases is represented for D30m CdSe/PbSe Janus NCs. The electron is distributed throughout the HNC whereas the hole localizes on the PbSe domain 140 Scheme 6.1 (A) Schematic of solar cell fabrication process. After depositing MPA capped QDs into TiOi CdS was coated through SILAR followed by partial cation exchange (CE) with Cu" to form the hole transporting CuS layer. Prolonged cation exchange decreases the PCE as shown in Figure 6.7. The major three recombination processes are from QD CB to redox electrolyte (process 1); from TiOo CB to redox electrolyte (process 2) and from TIOT CB to QD VB (process 3). The CdS passivation can prevent process 1 and 2 by passivating the QD and TiOo NPs. The CuS layer facilitates hole transfer to redox electrolyte thus prevents process 3 also. (B) Band energy diagram for TiOo/CdSSea/CdS/CuS/electrolyte to demonstrate facile electron injection from QD to the CB of TiO: and hole transfer from VB to electrolyte throgh CuS. The band energies of CdSSea was determined from CV, whereas for CdS and CuS values reported in literature were taken.'^ 190