The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Gavin Conibeer - One of the best experts on this subject based on the ideXlab platform.
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Generation of hot Carrier Population in colloidal silicon quantum dots for high-efficiency photovoltaics
Solar Energy Materials and Solar Cells, 2016Co-Authors: Pengfei Zhang, Yu Feng, Xiaoming Wen, Wenkai Cao, Rebecca J. Anthony, Uwe Kortshagen, Gavin Conibeer, Shujuan HuangAbstract:Abstract Hot Carrier generation in silicon (Si) quantum dots (QDs) is studied with power dependent continuous wave photoluminescence (CWPL) spectroscopy. By taking sub-band gap absorption into account, a modified Maxwell-Boltzmann-form equation was employed to achieve accurate theoretical fitting to the CWPL spectra of the Si QDs. As a fitting parameter, the excited Carrier temperature was calculated. A steady-state Carrier Population was revealed with a temperature 500 K above room temperature under illumination equivalent to one standard sun (100 mW/cm2). In addition, since the Carrier temperature increased with the power of illumination, a state filling effect is proposed as a reasonable cause for the elevated Carrier temperature by comparative study of the CWPL spectra of Si QDs with three different sizes. These Si QDs show great potential for one of the steps towards a practical hot Carrier solar cell (HCSC) device as high Carrier temperatures can be achieved by state filling under mild illumination.
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Quantification of hot Carrier thermalization in PbS colloidal quantum dots by power and temperature dependent photoluminescence spectroscopy
RSC Advances, 2016Co-Authors: Wenkai Cao, Pengfei Zhang, Xiaoming Wen, Zewen Zhang, Robert Patterson, Yuan Lin, Binesh Puthen Veetil, Qiuyang Zhang, Santosh Shrestha, Gavin ConibeerAbstract:PbS QDs are studied as attractive candidates to be applied as hot Carrier solar cell absorbers. The thermalization properties of PbS QDs are investigated with power and temperature dependent continuous wave photoluminescence (CWPL). Non-equilibrium hot Carrier Populations are generated by high energy laser excitation, the thermalization coefficient Q is estimated from the incident power dependent Carrier temperature. A non-equilibrium hot Carrier Population 200 K above the lattice temperature is detected at mild illumination intensity. A higher energy Carrier Population and an increasing Q value are observed with rising lattice temperatures. State filling effects are proposed as a possible cause of the generation of the non-equilibrium hot Carrier Population and an enhanced electron–phonon coupling strength is suggested to account for the faster Carrier cooling rate observed in closely packed Langmuir–Blodgett monolayer films. A thermalization coefficient, Q, as low as 6.55 W K−1 cm−2 was found for the drop cast sample and suggests that PbS QDs are good candidates for practical hot Carrier absorbers.
Xiaoming Wen - One of the best experts on this subject based on the ideXlab platform.
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extended hot Carrier lifetimes observed in bulk in0 265 0 02ga0 735n under high density photoexcitation
Applied Physics Letters, 2016Co-Authors: Yi Zhang, Xiaoming Wen, Zewen Zhang, Murad J Y Tayebjee, Suntrana Smyth, Miroslav Dvořak, Hongze Xia, Martin Heilmann, Yuanxun Liao, Todd L WilliamsonAbstract:We have investigated the ultrafast Carrier dynamics in a 1 μm bulk In0.265Ga0.735N thin film grown using energetic neutral atom-beam lithography/epitaxy molecular beam epitaxy. Cathodoluminescence and X-ray diffraction experiments are used to observe the existence of indium-rich domains in the sample. These domains give rise to a second Carrier Population and bi-exponential Carrier cooling is observed with characteristic lifetimes of 1.6 and 14 ps at a Carrier density of 1.3 × 1016 cm−3. A combination of band-filling, screening, and hot-phonon effects gives rise to a two-fold enhanced mono-exponential cooling rate of 28 ps at a Carrier density of 8.4 × 1018 cm−3. This is the longest Carrier thermalization time observed in bulk InGaN alloys to date.
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Generation of hot Carrier Population in colloidal silicon quantum dots for high-efficiency photovoltaics
Solar Energy Materials and Solar Cells, 2016Co-Authors: Pengfei Zhang, Yu Feng, Xiaoming Wen, Wenkai Cao, Rebecca J. Anthony, Uwe Kortshagen, Gavin Conibeer, Shujuan HuangAbstract:Abstract Hot Carrier generation in silicon (Si) quantum dots (QDs) is studied with power dependent continuous wave photoluminescence (CWPL) spectroscopy. By taking sub-band gap absorption into account, a modified Maxwell-Boltzmann-form equation was employed to achieve accurate theoretical fitting to the CWPL spectra of the Si QDs. As a fitting parameter, the excited Carrier temperature was calculated. A steady-state Carrier Population was revealed with a temperature 500 K above room temperature under illumination equivalent to one standard sun (100 mW/cm2). In addition, since the Carrier temperature increased with the power of illumination, a state filling effect is proposed as a reasonable cause for the elevated Carrier temperature by comparative study of the CWPL spectra of Si QDs with three different sizes. These Si QDs show great potential for one of the steps towards a practical hot Carrier solar cell (HCSC) device as high Carrier temperatures can be achieved by state filling under mild illumination.
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Quantification of hot Carrier thermalization in PbS colloidal quantum dots by power and temperature dependent photoluminescence spectroscopy
RSC Advances, 2016Co-Authors: Wenkai Cao, Pengfei Zhang, Xiaoming Wen, Zewen Zhang, Robert Patterson, Yuan Lin, Binesh Puthen Veetil, Qiuyang Zhang, Santosh Shrestha, Gavin ConibeerAbstract:PbS QDs are studied as attractive candidates to be applied as hot Carrier solar cell absorbers. The thermalization properties of PbS QDs are investigated with power and temperature dependent continuous wave photoluminescence (CWPL). Non-equilibrium hot Carrier Populations are generated by high energy laser excitation, the thermalization coefficient Q is estimated from the incident power dependent Carrier temperature. A non-equilibrium hot Carrier Population 200 K above the lattice temperature is detected at mild illumination intensity. A higher energy Carrier Population and an increasing Q value are observed with rising lattice temperatures. State filling effects are proposed as a possible cause of the generation of the non-equilibrium hot Carrier Population and an enhanced electron–phonon coupling strength is suggested to account for the faster Carrier cooling rate observed in closely packed Langmuir–Blodgett monolayer films. A thermalization coefficient, Q, as low as 6.55 W K−1 cm−2 was found for the drop cast sample and suggests that PbS QDs are good candidates for practical hot Carrier absorbers.
Jon M. Pikal - One of the best experts on this subject based on the ideXlab platform.
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Temperature dependence of intrinsic recombination coefficients in 1.3 μm InAsP/InP quantum-well semiconductor lasers
Applied Physics Letters, 2000Co-Authors: Jon M. Pikal, G.y. Robinson, Perumal Thiagarajan, Carmen S. Menoni, H. TemkinAbstract:In this letter, we report on the temperature dependence of the intrinsic recombination coefficients in long-wavelength quantum-well lasers. Unlike previous studies, we obtain the intrinsic recombination coefficients from Carrier lifetime measurements with a correction for the Carrier Population in the barrier and separate confinement heterostructure region. Our results show that this Carrier Population not only affects the value of the recombination coefficients obtained but also their temperature dependence. We measure a significant increase in the intrinsic Auger coefficient with temperature indicating that the frequently reported temperature insensitivity of this coefficient is likely due to Carriers spilling out of the wells at elevated temperatures and not an intrinsic property of the Auger process.
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Effect of indirect minima Carrier Population on the output characteristics of AlGaInP light-emitting diodes
Applied Physics Letters, 1999Co-Authors: Dinesh Patel, Jon M. Pikal, Carmen S. Menoni, K. J. Thomas, F. A. Kish, M. R. HueschenAbstract:We show that Carrier transfer to the indirect X level in the confining layer is responsible for most of the substantial decrease in the efficiency of AlGaInP light-emitting diodes (LEDs) operating at short wavelengths. Carrier transfer to the confining X level was obtained by reducing the separation between the AlGaInP direct Γ minimum and the X levels by varying the Al composition in the active region and by the application of hydrostatic pressure. Carrier transfer to the confining X level appeared as an additional peak in the electroluminescence (EL) and resulted in a significant decrease of the LED efficiency. A simple model of the EL emission that takes into account Carrier Population in the X minima was found to be in excellent agreement with the measured EL behavior.
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Carrier lifetime and recombination in long-wavelength quantum-well lasers
IEEE Journal of Selected Topics in Quantum Electronics, 1999Co-Authors: Jon M. Pikal, Perumal Thiagarajan, Carmen S. Menoni, H. Temkin, G.y. RobinsonAbstract:We present a novel analysis for correcting the measured differential Carrier lifetime to account for Carrier Population in both the barrier and separate confinement heterostructure (SCH) regions of quantum-well (QW) lasers. This analysis uses information obtained from the measured spontaneous emission spectra to correct the measured lifetime and obtain the intrinsic well lifetime. Once the intrinsic well lifetime is obtained, the intrinsic well recombination coefficients can also be obtained. We show that the Carrier Population in the barrier/SCH layers can significantly affect the measured Carrier lifetime and the extracted recombination coefficients. We also show that this analysis yields transparency Carrier density and differential gain numbers which are very different from those obtained with the traditional analysis and much closer to what is predicted for highly strained QW lasers. These differences indicate the importance of accounting for barrier/SCH Carriers on the measurement of basic QW laser material properties.
Pengfei Zhang - One of the best experts on this subject based on the ideXlab platform.
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Generation of hot Carrier Population in colloidal silicon quantum dots for high-efficiency photovoltaics
Solar Energy Materials and Solar Cells, 2016Co-Authors: Pengfei Zhang, Yu Feng, Xiaoming Wen, Wenkai Cao, Rebecca J. Anthony, Uwe Kortshagen, Gavin Conibeer, Shujuan HuangAbstract:Abstract Hot Carrier generation in silicon (Si) quantum dots (QDs) is studied with power dependent continuous wave photoluminescence (CWPL) spectroscopy. By taking sub-band gap absorption into account, a modified Maxwell-Boltzmann-form equation was employed to achieve accurate theoretical fitting to the CWPL spectra of the Si QDs. As a fitting parameter, the excited Carrier temperature was calculated. A steady-state Carrier Population was revealed with a temperature 500 K above room temperature under illumination equivalent to one standard sun (100 mW/cm2). In addition, since the Carrier temperature increased with the power of illumination, a state filling effect is proposed as a reasonable cause for the elevated Carrier temperature by comparative study of the CWPL spectra of Si QDs with three different sizes. These Si QDs show great potential for one of the steps towards a practical hot Carrier solar cell (HCSC) device as high Carrier temperatures can be achieved by state filling under mild illumination.
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Quantification of hot Carrier thermalization in PbS colloidal quantum dots by power and temperature dependent photoluminescence spectroscopy
RSC Advances, 2016Co-Authors: Wenkai Cao, Pengfei Zhang, Xiaoming Wen, Zewen Zhang, Robert Patterson, Yuan Lin, Binesh Puthen Veetil, Qiuyang Zhang, Santosh Shrestha, Gavin ConibeerAbstract:PbS QDs are studied as attractive candidates to be applied as hot Carrier solar cell absorbers. The thermalization properties of PbS QDs are investigated with power and temperature dependent continuous wave photoluminescence (CWPL). Non-equilibrium hot Carrier Populations are generated by high energy laser excitation, the thermalization coefficient Q is estimated from the incident power dependent Carrier temperature. A non-equilibrium hot Carrier Population 200 K above the lattice temperature is detected at mild illumination intensity. A higher energy Carrier Population and an increasing Q value are observed with rising lattice temperatures. State filling effects are proposed as a possible cause of the generation of the non-equilibrium hot Carrier Population and an enhanced electron–phonon coupling strength is suggested to account for the faster Carrier cooling rate observed in closely packed Langmuir–Blodgett monolayer films. A thermalization coefficient, Q, as low as 6.55 W K−1 cm−2 was found for the drop cast sample and suggests that PbS QDs are good candidates for practical hot Carrier absorbers.
Wenkai Cao - One of the best experts on this subject based on the ideXlab platform.
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Generation of hot Carrier Population in colloidal silicon quantum dots for high-efficiency photovoltaics
Solar Energy Materials and Solar Cells, 2016Co-Authors: Pengfei Zhang, Yu Feng, Xiaoming Wen, Wenkai Cao, Rebecca J. Anthony, Uwe Kortshagen, Gavin Conibeer, Shujuan HuangAbstract:Abstract Hot Carrier generation in silicon (Si) quantum dots (QDs) is studied with power dependent continuous wave photoluminescence (CWPL) spectroscopy. By taking sub-band gap absorption into account, a modified Maxwell-Boltzmann-form equation was employed to achieve accurate theoretical fitting to the CWPL spectra of the Si QDs. As a fitting parameter, the excited Carrier temperature was calculated. A steady-state Carrier Population was revealed with a temperature 500 K above room temperature under illumination equivalent to one standard sun (100 mW/cm2). In addition, since the Carrier temperature increased with the power of illumination, a state filling effect is proposed as a reasonable cause for the elevated Carrier temperature by comparative study of the CWPL spectra of Si QDs with three different sizes. These Si QDs show great potential for one of the steps towards a practical hot Carrier solar cell (HCSC) device as high Carrier temperatures can be achieved by state filling under mild illumination.
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Quantification of hot Carrier thermalization in PbS colloidal quantum dots by power and temperature dependent photoluminescence spectroscopy
RSC Advances, 2016Co-Authors: Wenkai Cao, Pengfei Zhang, Xiaoming Wen, Zewen Zhang, Robert Patterson, Yuan Lin, Binesh Puthen Veetil, Qiuyang Zhang, Santosh Shrestha, Gavin ConibeerAbstract:PbS QDs are studied as attractive candidates to be applied as hot Carrier solar cell absorbers. The thermalization properties of PbS QDs are investigated with power and temperature dependent continuous wave photoluminescence (CWPL). Non-equilibrium hot Carrier Populations are generated by high energy laser excitation, the thermalization coefficient Q is estimated from the incident power dependent Carrier temperature. A non-equilibrium hot Carrier Population 200 K above the lattice temperature is detected at mild illumination intensity. A higher energy Carrier Population and an increasing Q value are observed with rising lattice temperatures. State filling effects are proposed as a possible cause of the generation of the non-equilibrium hot Carrier Population and an enhanced electron–phonon coupling strength is suggested to account for the faster Carrier cooling rate observed in closely packed Langmuir–Blodgett monolayer films. A thermalization coefficient, Q, as low as 6.55 W K−1 cm−2 was found for the drop cast sample and suggests that PbS QDs are good candidates for practical hot Carrier absorbers.