Research On The Micro/nano-scale Thermal Radiation Of Optoelectronic Devices And Their Control Methods

Optoelectronic devices play an important role in the fields of biology sensoring,ernergy utilization,thermophotovoltiac,etc.With the developement of nano-technology,the optoelectronic devices tend to be integrated and miniaturized.The issues of micro/nano-scale thermal science become more prominent in optoelectronic devices.The thermal radiation properties are of vital importance to the performance of optoelectronic devices.There are many issues of micro/nano-scale thermal radiation to be ugently solved in the optoelectronic devices,such as efficient utilization of solar energy,control of radiation properties of thermal emitter,thermoelectric utilization,spacecraft thermal control and so on.Because various near-field effects could be excited in the micro/nano-scale thermal radiation,such as surface plasmon polaritions,micro-cavity effect,magnetic polaritons,coherent radiation and so on,the traditional theories of thermal radiation are not applicable.Therefore,it is of great interest to the design and application of optoelectronic devices by understanding,research and control of micro/nano-scale thermal radiation.In this thesis,the micro-structured surfaces are designed for the optoelectronic devices.The control mechanisms of thermal radiation of optoelectronic devices are revealed.The effects of structral parameters,incident angle and polarization on the thermal radiation of optoelectronic devices are analyzed.The control methods of thermal radiation of optoelectronic devices are established.The investigations can provide theoretical guidance for the design and application of efficient optoelectronic devices.The main contents of this thesis include following aspects:1 Research on the physical mechanism of magnetic polaritonsMetal/insulator/metal grating structure is widely used in the optoelectronic devices of thermal emitter,light-emitting diode,thermal detector,etc.Magnetic polaritons are generally excited to induece the resonance in metal/insulator/metal grating structured surface.The omnidirectional thermal radiation properties could be realized by this reasonce.However,the physical mechanism of the reasonance in metal/insulator/metal grating structure is still debatable.We calculate the thermal radiation properties of metal/insulator/metal grating structured surface with rigorous-coupled wave-analysis method.Simutaneously the resonant frequencies are predicted by the dipersion relation and equivalent LC circuit.The predicted resonant frequencies and compared with the radiation peaks to analyze the physical mechanism of magnetic polaritons.The effect of geometry parameters on the thermal radiation of metal/insulator/metal grating structured surface are dicussed and the electromagnetic field distributions in the metal/insulator/metal grating structured surface with different geometry parameters are calculated to verify the physical mechanism of magnetic polaritons furthermore.2 Research on the thermal radiation of omnidiretional narrowband emitterNarrowband emitter is a kind of optoelectronic devices playing an important role in biology engineering,sensing,and energy utilization,etc.The narrowband thermal radiation can be induced by the excitation of surface plasmon polartions,Fabry-Perot resonance and micro-cavity resonance effect.However,the narrowband thermal radiations caused by surface plasmon polaritons and Fabry-Perot resonance are always incident angle-dependent.The narrowband thermal radiation induced by the excitation of micro-cavity resonace effect is omnidiretional.Presently,the metal material is generally used to to excite micro-cavity effect on the micro-strcutured surface and the angle range is not wide enough.Based on the micro-cavity resonsnce effect,we propose a periodic miciro-structured surface for the narrowband thermal radiation.The metal clapboard of micro-cavity is replaced with doped silicon clapboard.The resonance peak can be controlled by changing the geometry size of micro-cavity.The omnidirectional performance of this structured surface is better than that of metal micro-cavity structured surface.3 Research on the design method of omnirectional perovskite solar cellSolar cell is an important kind of optoelectronic devices in the field of erngy utilization.Perovskite solar cell,which acts as a novel device for solar energy utilization,is attractive due to the high energy conversion efficiency and low fabrication cost.Enhanced light-trapping is the precondition of increasing the energy conversion efficiency.In order to realize the better light-trapping of perovskite solar cell,five different structured surfaces are designed for the perovskite cell.The radiation properties of five structured surfaces are calculated by the finite-difference time-domain method.The electric properties are obtained by solving the coupled Possion equation,continuity equation and drift-diffusion equations.The radiation and electric properties of five structured surfaces are compared to select a best structured surface for perovskite solar cell.The effect of structural size on the cell performance is investigated.The incident angle-dependence and polarization-dependence are analyzed.Thereby,the design method of omnidirectional perovskite solar cell is established.4 Research on the control method of broadband and omnidirectional thermal radiation of photovoltaic-thermoelectric systemsIt is of great significance for full-spectrum utilization of solar energy to realize broadband and omnidirectional thermal radiation.The energy conversion efficiency of photovoltaic-thermoelectric hybrid system can be effectively increased by enhancing the transmission in intrared band,in which the photons are utilized by thermoelectric module,under the premise of high absorption in visible band.The periodic structured surface is designed with moth-eye structure and thin film for omnidirectional broadband thermal radiation control.The reflection,transmission and absorption of micro-structured surface are calculated by the finite-difference time-domain method.The effects of structural parameters on the broadband thermal radiation properties are discussed.The incident angle-dependence and polarization-dependence are analyzed.5 Experimental research on the control of broadband and omnidirectional thermal radiation of photovoltaic-thermoelectric systemsThe micro-structured surface of Si solar cell is designed according to the thermal radiation requirement of photovoltaic-thermoelectric hybrid system.The designed structured surface is fabricated with plasma etching,lye etching and magnetron sputtering methods based on the self-assembly monolayer PS spheres mask.The surface topography of the prepared sample is observed by scanning electric microscopy.The effects of eaching time,flow of etching gas and eaching power on the surface topography and spectral performance of structured surface are analyzed.The thermal radiation properties of the prepared sample are measured by the spectrophotometer at different incident angles and polarization states.