Optimizing the Photovoltaic Properties of CdTe Quantum Dot–Porphyrin Nanocomposites: A Theoretical Study
2016
Rajbanshi, Biplab | Sarkar, Pranab
By using the self-consistent charge density functional tight binding method, we explore the photovoltaic properties of CdTe quantum dot (CdTeQD)–porphyrin nanocomposites. It is well-known that for dye-sensitized solar cell (DSSCs) applications, the composite system should have a type-II band alignment that hinders the recombination of charge carriers, thereby improving the photovoltaic performance. The emphasis of our tight-binding calculations is to find the suitable CdTeQD–porphyrin nanocomposites that can offer better performance for solar energy conversion. By analyzing the electronic energy levels of the composite systems we have shown that the axially coordinated Zn-tetraphenylporphyrin (ZnTPP) functionalized CdTe quantum dot (ZnTPP–CdTeQD) nanocomposites are really promising materials for application in DSSCs, as they produce type-II band alignment for all the composites irrespective of the size of CdTeQDs. The time-dependent density functional theory (TDDFT) calculations demonstrate that the size of CdTeQD plays a crucial role in improving the charge transfer properties from the ZnTPP to the QD. We also tried to give a qualitative prediction about the performance of ZnTPP–CdTeQD nanocomposites in light harvesting device using some empirical relations coupled with TDDFT calculations. We suggest that the ZnTPP–CdTeQD nanocomposites with moderate size of QD will show high performance for light harvesting rather than too big or too small one.
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