We investigate the thermal characteristics of standard organic light-emitting diodes (OLEDs) using a simple and clear 1D thermal model based on the basic heat transfer theory. The thermal model can accurately estima...We investigate the thermal characteristics of standard organic light-emitting diodes (OLEDs) using a simple and clear 1D thermal model based on the basic heat transfer theory. The thermal model can accurately estimate the device temperature, which is linearly with electrical input power. The simulation results show that there is almost no temperature gradient within the OLED device working under steady state conditions. Furthermore, thermal analysis simulation results show that the surface properties (convective heat transfer coetficient and surface emissivity) of the substrate or cathode can significantly affect the temperature distribution of the OLED.展开更多
High efficiency, stable organic light-emitting diodes (OLEDs) based on 2-pheyl-4'-carbazole-9-H-Thioxanthen-9- one-10, 10-dioxide (TXO-PhCz) with different doping concentration are constructed. The stability of t...High efficiency, stable organic light-emitting diodes (OLEDs) based on 2-pheyl-4'-carbazole-9-H-Thioxanthen-9- one-10, 10-dioxide (TXO-PhCz) with different doping concentration are constructed. The stability of the encap- sulated devices are investigated in detail. The devices with the 10 wt% doped TXO-PhCz emitter layer (EML) show the best performance with a current efficiency of 52.1 cd/A, a power efficiency of 32.71re^W, and an external quantum efficiency (EQE) of 17.7%. The devices based on the lOwt%-doped TXO-PhCz EML show the best operational stability with a half-life time (LTSO) of 8Oh, which is 8 h longer than that of the reference devices based on fac-tris(2-phenylpyridinato)iridium( Ⅲ) (Ir(ppy)a). These indicate excellent stability of TXO-PhCz for redox and oxidation processes under electrical excitation and TXO-PhCz can be potentially used as the emitters for OLEDs with high efficiency and excellent stability. The high-performance device based on TXO-PhCz with high stability can be further improved by the optimization of the encapsulation technology and the development of a new host for TXO-PhCz.展开更多
The application of thermal diodes,which allow heat to flow more readily in one direction than the other,is an important way to reduce energy consumption in buildings and enhance the battery heat dissipation of electri...The application of thermal diodes,which allow heat to flow more readily in one direction than the other,is an important way to reduce energy consumption in buildings and enhance the battery heat dissipation of electric vehicles.Depending on various factors including the specific design,materials used,and operating conditions,the convective thermal diode can exhibit the best thermal rectification effect in intended applications compared to the other thermal diodes.In this study,a novel convective thermal diode with a wick was proposed based on the phase change heat transfer mechanism.This design takes advantage of both capillary forces provided by the wick and gravity to achieve enhanced unidirectional heat transfer performance for the designed convective thermal diode.The effect of the filling liquid ratio on the thermal performance of the thermal diode was experimentally investigated,which was in good agreement with the theoretical analysis.The research findings showed that with an optimal liquid filling ratio of 140%,the thermal diode with a wick can achieve a better thermal rectification ratio when subjected to a lower heating power,and the maximum thermal rectification ratio of 21.76 was experimentally achieved when the heating power of the thermal diode was 40 W.展开更多
The thermal characteristics of 808 nm Al Ga As/Ga As laser diodes(LDs) are analyzed via electrical transient measurements and infrared thermography. The temperature rise and thermal resistance are measured at variou...The thermal characteristics of 808 nm Al Ga As/Ga As laser diodes(LDs) are analyzed via electrical transient measurements and infrared thermography. The temperature rise and thermal resistance are measured at various input currents and powers. From the electrical transient measurements, it is found that there is a significant reduction in thermal resistance with increasing power because of the device power conversion efficiency. The component thermal resistance that was obtained from the structure function showed that the total thermal resistance is mainly composed of the thermal resistance of the sub-mount rather than that of the LD chip, and the thermal resistance of the sub-mount decreases with increasing current. The temperature rise values are also measured by infrared thermography and are calibrated based on a reference image, with results that are lower than those determined by electrical transient measurements. The difference in the results is caused by the limited spatial resolution of the measurements and by the signal being captured from the facet rather than from the junction of the laser diode.展开更多
Due to its great potential applications in thermal management,heat control,and quantum information,phononics has gained increasing attentions since the first publication in Rev.Mod.Phys.841045(2012).Many theoretical a...Due to its great potential applications in thermal management,heat control,and quantum information,phononics has gained increasing attentions since the first publication in Rev.Mod.Phys.841045(2012).Many theoretical and experimental progresses have been achieved in the past decade.In this paper,we first give a critical review of the progress in thermal diodes and transistors,especially in classical regime.Then,we give a brief introduction to the new developing research directions such as topological phononics and quantum phononics.In the third part,we discuss the potential applications.Last but not least,we point out the outlook and challenges ahead.展开更多
In order to improve the output power and increase the lifetime of laser diodes,expansion-matched submounts were investigated by finite element analysis.The submount was designed as sandwiched structure.By varying the ...In order to improve the output power and increase the lifetime of laser diodes,expansion-matched submounts were investigated by finite element analysis.The submount was designed as sandwiched structure.By varying the vertical structure and material of the middle layer,the thermal expansion behavior on the mounting surface was simulated to obtain the expansion-matched design.In addition,the thermal performance of laser diodes packaged by different submounts was compared.The numerical results showed that,changing the thickness ratio of surface copper to middle layer will lead the stress and junction temperature to the opposite direction.Thus compromise needs to be made in the design of the vertical structure.In addition,the silicon carbide(SiC) is the most promising material candidate for the middle layer among the materials discussed in this paper.The simulated results were aimed at providing guidance for the optimal design of sandwich-structure submounts.展开更多
Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of b...Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of blue TADF OLEDs are two key bottlenecks limiting the development of solution processable displays and white light sources.This work presents a solution-processed OLED using a blue-emitting TADF small molecule bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(DMAC-DPS)as an emitter.We comparatively investigated the effects of single host poly(Nvinylcarbazole)(PVK)and a co-host of 60%PVK and 30%2,2′-(1,3-phenylene)-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7)on the device performance(the last 10%is emitter DMAC-DPS).The co-host device shows lower turn-on voltage,similar maximum luminance,and much slower external quantum efficiency(EQE)rolloff.In other words,device stability improved by doping OXD-7 into PVK,and the device impedance simultaneously and significantly reduced from 8.6103 to 4.2103 W at 1000 Hz.Finally,the electroluminescent stability of the co-host device was significantly enhanced by adjusting the annealing temperature.展开更多
8 mil×10 mil InGaN/GaN blue LEDs with indium tin oxide(ITO) emitting at 460 nm were fabricated. A vacuum evaporation technique was adopted to deposit ITO on P-GaN with thickness of 240 nm.The electrical and opt...8 mil×10 mil InGaN/GaN blue LEDs with indium tin oxide(ITO) emitting at 460 nm were fabricated. A vacuum evaporation technique was adopted to deposit ITO on P-GaN with thickness of 240 nm.The electrical and optical properties of ITO films on P-GaN wafers,as well as rapid thermal annealing(RTA) effects at different temperatures(100 to 550℃) were analyzed and compared.It was found that resistivity of 450℃RTA was as low as 1.19×10^(-4)Ω·cm,along with a high transparency of 94.17%at 460 nm.AES analysis indicated the variation of oxygen content after 450℃annealing,and ITO contact resistance showed a minimized value of 3.9×10^(-3)Ω·cm^2.With 20 mA current injection,it was found that forward voltage and output power were 3.14 V and 12.57 mW.Furthermore,maximum luminous flux of 0.49 lm of ITO RTA at 550℃was measured,which is the consequence of a higher transparency.展开更多
A readout integrated circuit (ROIC) for a MEMS (microelectromechanical system)-array-based focal plane (MAFP) intended for imaging applications is presented. The ROIC incorporates current sources for diode de- t...A readout integrated circuit (ROIC) for a MEMS (microelectromechanical system)-array-based focal plane (MAFP) intended for imaging applications is presented. The ROIC incorporates current sources for diode de- tectors, scanners, timing sequence controllers, differential buffered injection-capacitive trans-impedance amplifier (DBI-CTIA) and 10-bit cyclic ADCs, and is integrated with MAFP using 3-D integration technology. A small-signal equivalent model is built to include thermal detectors into circuit simulations. The biasing current is optimized in terms of signal-to-noise ratio and power consumption. Layout design is tailored to fulfill the requirements of 3-D integration and to adapt to the size of MAFP elements, with not all but only the 2 bottom metal layers to complete nearly all the interconnections in DBI-CTIA and ADC in a 40/zm wide column. Experimental chips are designed and fabricated in a 0.35 μm CMOS mixed signal process, and verified in a code density test of which the results indicate a (0.29/-0.31) LSB differential nonlinearity (DNL) and a (0.61/-0.45) LSB integral nonlinearity (INL). Spectrum analysis shows that the effective number of bits (ENOB) is 9.09. The RO1C consumes 248 mW of power at most if not to cut off quiescent current paths when not needed.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11304247the Shaanxi Provincial Research Plan for Young Scientific and Technological New Stars(No 2015KJXX-40)the Youth Foundation of Xi’an University of Post&Telecommunication under Grant Nos 1011215 and 1010473
文摘We investigate the thermal characteristics of standard organic light-emitting diodes (OLEDs) using a simple and clear 1D thermal model based on the basic heat transfer theory. The thermal model can accurately estimate the device temperature, which is linearly with electrical input power. The simulation results show that there is almost no temperature gradient within the OLED device working under steady state conditions. Furthermore, thermal analysis simulation results show that the surface properties (convective heat transfer coetficient and surface emissivity) of the substrate or cathode can significantly affect the temperature distribution of the OLED.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61420106002,51373189,61178061,and 61227008the Hundred Talents Program of the Chinese Academy of Sciences,the National Basic Research Program of China under Grant No 2014CB932600the Start-Up Fund of the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences
文摘High efficiency, stable organic light-emitting diodes (OLEDs) based on 2-pheyl-4'-carbazole-9-H-Thioxanthen-9- one-10, 10-dioxide (TXO-PhCz) with different doping concentration are constructed. The stability of the encap- sulated devices are investigated in detail. The devices with the 10 wt% doped TXO-PhCz emitter layer (EML) show the best performance with a current efficiency of 52.1 cd/A, a power efficiency of 32.71re^W, and an external quantum efficiency (EQE) of 17.7%. The devices based on the lOwt%-doped TXO-PhCz EML show the best operational stability with a half-life time (LTSO) of 8Oh, which is 8 h longer than that of the reference devices based on fac-tris(2-phenylpyridinato)iridium( Ⅲ) (Ir(ppy)a). These indicate excellent stability of TXO-PhCz for redox and oxidation processes under electrical excitation and TXO-PhCz can be potentially used as the emitters for OLEDs with high efficiency and excellent stability. The high-performance device based on TXO-PhCz with high stability can be further improved by the optimization of the encapsulation technology and the development of a new host for TXO-PhCz.
基金supported by the National Natural Science Foundation of China(Grant No.52208124)Hubei Provincial Key Research and Design Project(Grant No.2020BAB129)Scientific Research Foundation of Wuhan University of Technology(Grant No.40120237 and 40120551)。
文摘The application of thermal diodes,which allow heat to flow more readily in one direction than the other,is an important way to reduce energy consumption in buildings and enhance the battery heat dissipation of electric vehicles.Depending on various factors including the specific design,materials used,and operating conditions,the convective thermal diode can exhibit the best thermal rectification effect in intended applications compared to the other thermal diodes.In this study,a novel convective thermal diode with a wick was proposed based on the phase change heat transfer mechanism.This design takes advantage of both capillary forces provided by the wick and gravity to achieve enhanced unidirectional heat transfer performance for the designed convective thermal diode.The effect of the filling liquid ratio on the thermal performance of the thermal diode was experimentally investigated,which was in good agreement with the theoretical analysis.The research findings showed that with an optimal liquid filling ratio of 140%,the thermal diode with a wick can achieve a better thermal rectification ratio when subjected to a lower heating power,and the maximum thermal rectification ratio of 21.76 was experimentally achieved when the heating power of the thermal diode was 40 W.
基金Project supported by the National Natural Science Foundation of China(Nos.61376077,61201046,61204081)
文摘The thermal characteristics of 808 nm Al Ga As/Ga As laser diodes(LDs) are analyzed via electrical transient measurements and infrared thermography. The temperature rise and thermal resistance are measured at various input currents and powers. From the electrical transient measurements, it is found that there is a significant reduction in thermal resistance with increasing power because of the device power conversion efficiency. The component thermal resistance that was obtained from the structure function showed that the total thermal resistance is mainly composed of the thermal resistance of the sub-mount rather than that of the LD chip, and the thermal resistance of the sub-mount decreases with increasing current. The temperature rise values are also measured by infrared thermography and are calibrated based on a reference image, with results that are lower than those determined by electrical transient measurements. The difference in the results is caused by the limited spatial resolution of the measurements and by the signal being captured from the facet rather than from the junction of the laser diode.
基金supported by the National Natural Science Foundation of China(Grant No.62004211)Shenzhen Science and Technology Program(Grant No.RCBS20200714114858221)
文摘Due to its great potential applications in thermal management,heat control,and quantum information,phononics has gained increasing attentions since the first publication in Rev.Mod.Phys.841045(2012).Many theoretical and experimental progresses have been achieved in the past decade.In this paper,we first give a critical review of the progress in thermal diodes and transistors,especially in classical regime.Then,we give a brief introduction to the new developing research directions such as topological phononics and quantum phononics.In the third part,we discuss the potential applications.Last but not least,we point out the outlook and challenges ahead.
文摘In order to improve the output power and increase the lifetime of laser diodes,expansion-matched submounts were investigated by finite element analysis.The submount was designed as sandwiched structure.By varying the vertical structure and material of the middle layer,the thermal expansion behavior on the mounting surface was simulated to obtain the expansion-matched design.In addition,the thermal performance of laser diodes packaged by different submounts was compared.The numerical results showed that,changing the thickness ratio of surface copper to middle layer will lead the stress and junction temperature to the opposite direction.Thus compromise needs to be made in the design of the vertical structure.In addition,the silicon carbide(SiC) is the most promising material candidate for the middle layer among the materials discussed in this paper.The simulated results were aimed at providing guidance for the optimal design of sandwich-structure submounts.
基金the National Key Research and Development Program of China(No.2017YFB0404404)the Open Fund of State Key Laboratory of Luminescent Materials and Devices(South China University of Technology),China。
文摘Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of blue TADF OLEDs are two key bottlenecks limiting the development of solution processable displays and white light sources.This work presents a solution-processed OLED using a blue-emitting TADF small molecule bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(DMAC-DPS)as an emitter.We comparatively investigated the effects of single host poly(Nvinylcarbazole)(PVK)and a co-host of 60%PVK and 30%2,2′-(1,3-phenylene)-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7)on the device performance(the last 10%is emitter DMAC-DPS).The co-host device shows lower turn-on voltage,similar maximum luminance,and much slower external quantum efficiency(EQE)rolloff.In other words,device stability improved by doping OXD-7 into PVK,and the device impedance simultaneously and significantly reduced from 8.6103 to 4.2103 W at 1000 Hz.Finally,the electroluminescent stability of the co-host device was significantly enhanced by adjusting the annealing temperature.
基金supported by the National High Technology Research and Development Program of China(No.2009AA03A 1A3)the National Key Technologies R&D Program of China(No.2011BAE01B14)
文摘8 mil×10 mil InGaN/GaN blue LEDs with indium tin oxide(ITO) emitting at 460 nm were fabricated. A vacuum evaporation technique was adopted to deposit ITO on P-GaN with thickness of 240 nm.The electrical and optical properties of ITO films on P-GaN wafers,as well as rapid thermal annealing(RTA) effects at different temperatures(100 to 550℃) were analyzed and compared.It was found that resistivity of 450℃RTA was as low as 1.19×10^(-4)Ω·cm,along with a high transparency of 94.17%at 460 nm.AES analysis indicated the variation of oxygen content after 450℃annealing,and ITO contact resistance showed a minimized value of 3.9×10^(-3)Ω·cm^2.With 20 mA current injection,it was found that forward voltage and output power were 3.14 V and 12.57 mW.Furthermore,maximum luminous flux of 0.49 lm of ITO RTA at 550℃was measured,which is the consequence of a higher transparency.
基金Project supported by by National Natural Science Foundation of China(No.61271130)the Beijing Municipal Science and Tech Project(No.D13110100290000)+1 种基金the Tsinghua University Initiative Scientific Research Program(No.20131089225)the Shenzhen Science and Technology Development Fund(No.CXZZ20130322170740736)
文摘A readout integrated circuit (ROIC) for a MEMS (microelectromechanical system)-array-based focal plane (MAFP) intended for imaging applications is presented. The ROIC incorporates current sources for diode de- tectors, scanners, timing sequence controllers, differential buffered injection-capacitive trans-impedance amplifier (DBI-CTIA) and 10-bit cyclic ADCs, and is integrated with MAFP using 3-D integration technology. A small-signal equivalent model is built to include thermal detectors into circuit simulations. The biasing current is optimized in terms of signal-to-noise ratio and power consumption. Layout design is tailored to fulfill the requirements of 3-D integration and to adapt to the size of MAFP elements, with not all but only the 2 bottom metal layers to complete nearly all the interconnections in DBI-CTIA and ADC in a 40/zm wide column. Experimental chips are designed and fabricated in a 0.35 μm CMOS mixed signal process, and verified in a code density test of which the results indicate a (0.29/-0.31) LSB differential nonlinearity (DNL) and a (0.61/-0.45) LSB integral nonlinearity (INL). Spectrum analysis shows that the effective number of bits (ENOB) is 9.09. The RO1C consumes 248 mW of power at most if not to cut off quiescent current paths when not needed.