In pursuit of an abundant, inexpensive and stable counter electrode as an alternative to platinum... more In pursuit of an abundant, inexpensive and stable counter electrode as an alternative to platinum for dye-sensitized solar cells (DSSCs), we report a new, low-cost substitute material. Here for the first time, we demonstrate that V 2 O 5 can be used as a counter electrode material in DSSCs. We note that the efficiency of DSSCs with commercial V 2 O 5 and hydrothermal treated V 2 O 5 are upto 1.2% and 1.6%, respectively. The results indicate that, with optimization, V 2 O 5 can be a promising choice to replace platinum from a cost perspective. The innovation of new economical counter electrodes offers a potential way to cut down the industrial costs which is crucial for large-scale production and commercial applications of DSSCs.
Physica Status Solidi A-applications and Materials Science, 2010
An investigation of InN layers grown on GaN templates by molecular beam epitaxy (MBE) has been ca... more An investigation of InN layers grown on GaN templates by molecular beam epitaxy (MBE) has been carried out by X-ray diffraction (XRD), Raman spectroscopy (RS) and photoluminescence (PL). A good correlation is noticed between their crystalline quality and optical properties. The best samples exhibit a PL emission between 0.6 and 0.7 eV. The surface structure was quite different from one sample to the other, pointing out to a critical role of the growth conditions, which probably need to be tightly optimized for a good reproducibility.
Due to its small band-gap and its high mobility, InN is a promising material for a large number o... more Due to its small band-gap and its high mobility, InN is a promising material for a large number of key applications like band-gap engineering for high efficiency solar cells, light emitting diodes, and high speed devices. Unfortunately, it has been reported that this material exhibits strong surface charge accumulation which may depend on the type of surface. Current investigations are conducted in order to explain the mechanisms which govern such a behavior and to look for ways of avoiding it and/or finding applications that may use such an effect. In this framework, low frequency noise measurements have been performed at different temperatures on patterned MBE grown InN layers. The evolution of the 1/f noise level with temperature in the 77 K-300 K range is consistent with carrier number fluctuations thus indicating surface mechanisms: the surface charge accumulation is confirmed by the noise measurements.
We report on the nonlinear optical absorption of InN/InxGa1-xN (x=0.8,0.9) multiple-quantum-well ... more We report on the nonlinear optical absorption of InN/InxGa1-xN (x=0.8,0.9) multiple-quantum-well structures characterized at 1.55 μm by the Z-scan method in order to obtain the effective nonlinear absorption coefficient (α2) of the samples at high repetition rate. Saturable absorption is observed for the sample with x=0.9, with an effective α2~-9×103 cm/GW for the studied optical regime. For lower In content in the barrier, reverse saturable absorption is observed, which is attributed to two-photon absorption.
In pursuit of an abundant, inexpensive and stable counter electrode as an alternative to platinum... more In pursuit of an abundant, inexpensive and stable counter electrode as an alternative to platinum for dye-sensitized solar cells (DSSCs), we report a new, low-cost substitute material. Here for the first time, we demonstrate that V 2 O 5 can be used as a counter electrode material in DSSCs. We note that the efficiency of DSSCs with commercial V 2 O 5 and hydrothermal treated V 2 O 5 are upto 1.2% and 1.6%, respectively. The results indicate that, with optimization, V 2 O 5 can be a promising choice to replace platinum from a cost perspective. The innovation of new economical counter electrodes offers a potential way to cut down the industrial costs which is crucial for large-scale production and commercial applications of DSSCs.
Physica Status Solidi A-applications and Materials Science, 2010
An investigation of InN layers grown on GaN templates by molecular beam epitaxy (MBE) has been ca... more An investigation of InN layers grown on GaN templates by molecular beam epitaxy (MBE) has been carried out by X-ray diffraction (XRD), Raman spectroscopy (RS) and photoluminescence (PL). A good correlation is noticed between their crystalline quality and optical properties. The best samples exhibit a PL emission between 0.6 and 0.7 eV. The surface structure was quite different from one sample to the other, pointing out to a critical role of the growth conditions, which probably need to be tightly optimized for a good reproducibility.
Due to its small band-gap and its high mobility, InN is a promising material for a large number o... more Due to its small band-gap and its high mobility, InN is a promising material for a large number of key applications like band-gap engineering for high efficiency solar cells, light emitting diodes, and high speed devices. Unfortunately, it has been reported that this material exhibits strong surface charge accumulation which may depend on the type of surface. Current investigations are conducted in order to explain the mechanisms which govern such a behavior and to look for ways of avoiding it and/or finding applications that may use such an effect. In this framework, low frequency noise measurements have been performed at different temperatures on patterned MBE grown InN layers. The evolution of the 1/f noise level with temperature in the 77 K-300 K range is consistent with carrier number fluctuations thus indicating surface mechanisms: the surface charge accumulation is confirmed by the noise measurements.
We report on the nonlinear optical absorption of InN/InxGa1-xN (x=0.8,0.9) multiple-quantum-well ... more We report on the nonlinear optical absorption of InN/InxGa1-xN (x=0.8,0.9) multiple-quantum-well structures characterized at 1.55 μm by the Z-scan method in order to obtain the effective nonlinear absorption coefficient (α2) of the samples at high repetition rate. Saturable absorption is observed for the sample with x=0.9, with an effective α2~-9×103 cm/GW for the studied optical regime. For lower In content in the barrier, reverse saturable absorption is observed, which is attributed to two-photon absorption.
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Papers by geeta Mutta