Ganesh Markad - Academia.edu (original) (raw)
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N. Shankaran Nair Research center for nanotechnology and Bionanotechnology
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Papers by Ganesh Markad
Nano Letters, 2017
Colloidal all inorganic CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) have emerged to be an excellen... more Colloidal all inorganic CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) have emerged to be an excellent material for applications in light emission, photovoltaics, and photocatalysis. Efficient interfacial transfer of photogenerated electrons and holes are essential for a good photovoltaic and photocatalytic material. Using time-resolved terahertz (THz) spectroscopy (TRTS) we have measured the kinetics of photogenerated electron and hole transfer processes in CsPbBr 3 NCs in presence of benzoquinone (BQ) and phenothiazine (PTZ) molecules as electron and hole acceptors, respectively. Efficient hot electron/hole transfer with a sub-300 fs timescale is the major channel of carrier transfer, thus overcomes the problem related to Auger recombination. A secondary transfer of thermalized carriers also takes place with time scales of 20-50 ps for electrons and 137-166 ps for holes. This work suggests that suitable interfaces of
The Journal of Physical Chemistry C, 2016
Nanoscale heterojunctions with type-II band alignment can efficiently separate photogenerated ele... more Nanoscale heterojunctions with type-II band alignment can efficiently separate photogenerated electron-hole pair, and therefore find applications in solar cells and photocatalysis. Here we prepare a nano-junction in the form of Ag 2 S-AgInS 2 hetero dimer nanocrystal that does not contain toxic Cd and Pb. A combination of photophysics, cyclic voltammetry and quantum dot sensitized solar cell properties show that the junction/interface has a type-I band alignment, but still electron-hole separation takes place with efficacy across the interface because of defect states. The electron gets localized in a defect state within AgInS 2 part and the hole resides in the Ag 2 S part of the hetero dimer nanocrystal. This type-II-like defect mediated electron-hole separation, irrespective of the nature interfacial band alignment, is an interesting phenomenon, and can be utilized to tune optoelectronic properties of heterostructured nanocrystals. For example, very long (13 µS) photoluminescence lifetime has been observed for Ag 2 S-AgInS 2 hetero dimer nanocrystals because of this defectmediated spatial separation of electron and hole wavefunctions, which in turn improve the solar cell efficiency by more than three times compared to AgInS 2 nanocrystals.
Nano Letters, 2017
Colloidal all inorganic CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) have emerged to be an excellen... more Colloidal all inorganic CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) have emerged to be an excellent material for applications in light emission, photovoltaics, and photocatalysis. Efficient interfacial transfer of photogenerated electrons and holes are essential for a good photovoltaic and photocatalytic material. Using time-resolved terahertz (THz) spectroscopy (TRTS) we have measured the kinetics of photogenerated electron and hole transfer processes in CsPbBr 3 NCs in presence of benzoquinone (BQ) and phenothiazine (PTZ) molecules as electron and hole acceptors, respectively. Efficient hot electron/hole transfer with a sub-300 fs timescale is the major channel of carrier transfer, thus overcomes the problem related to Auger recombination. A secondary transfer of thermalized carriers also takes place with time scales of 20-50 ps for electrons and 137-166 ps for holes. This work suggests that suitable interfaces of
The Journal of Physical Chemistry C, 2016
Nanoscale heterojunctions with type-II band alignment can efficiently separate photogenerated ele... more Nanoscale heterojunctions with type-II band alignment can efficiently separate photogenerated electron-hole pair, and therefore find applications in solar cells and photocatalysis. Here we prepare a nano-junction in the form of Ag 2 S-AgInS 2 hetero dimer nanocrystal that does not contain toxic Cd and Pb. A combination of photophysics, cyclic voltammetry and quantum dot sensitized solar cell properties show that the junction/interface has a type-I band alignment, but still electron-hole separation takes place with efficacy across the interface because of defect states. The electron gets localized in a defect state within AgInS 2 part and the hole resides in the Ag 2 S part of the hetero dimer nanocrystal. This type-II-like defect mediated electron-hole separation, irrespective of the nature interfacial band alignment, is an interesting phenomenon, and can be utilized to tune optoelectronic properties of heterostructured nanocrystals. For example, very long (13 µS) photoluminescence lifetime has been observed for Ag 2 S-AgInS 2 hetero dimer nanocrystals because of this defectmediated spatial separation of electron and hole wavefunctions, which in turn improve the solar cell efficiency by more than three times compared to AgInS 2 nanocrystals.