The Design And Research On Light-collecting Performance Of Luminescent Solar Concentrators Based On Quantum Dots

With the rapid development of concentrator photovoltaic（CPV）technology,both the concepts of net zero-energy buildings（NZEBs）and building-integrated photovoltaic（BIPV）have attracted widespread attentions from researchers.The traditional CPV device is mainly composed of a series of arrays of mirror and a convex lens.In order to avoid certain mirrors shading others,the set-up of traditional CPV device needs to waste a lot of floor space.What is more,the specific solar-tracking systems will greatly increase costs of traditional CPV because the arrays of mirror and a convex lens need to move along the solar angle in real time.Planar luminescent solar concentrators（LSCs）can effectively solve these above problems.Not only can planar LSCs absorb direct radiation,but also absorb surrounding scattered radiation.Therefore,no expensive and precise solar-tracking systems are needed.On the other hand,the infrared light will not be directly irradiated on the solar cells,so the obvious thermal effect reduces.By transforming traditional glass window systems into translucent photovoltaic windows,LSCs effectively transform the exterior walls of urban buildings into distributed energy generating units,which is very suitable for the BIPV.In the current design of LSC device,the ranges of parameters value are very large and the relationship between the values of related parameters and optical efficiency is in a non-linear way,so it’s difficult to find the optimal parameters,which limits the improvement of LSCs’comprehensive performance.Meanwhile,the luminophor materials in LSCs have some problems such as poor stability,low quantum yield and poor environmental protection,which hinder their application and promotion on BIPV.Therefore,in order to address the above problems,this thesis utilizes the Monte Carlo ray-tracing model to simulate photon transmission.In regard to optical efficiency and stability of the LSCs,the thesis conducts researches by doping all-inorganic perovskite quantum dots,carbon quantum dots and lead sulfide quantum dots and deeply analyzes the photon transmission mechanism in LSCs.To sum up,the main research content of the thesis is listed as follow:The Monte Carlo ray-tracing model is used to explore and simulate the photon transport mechanism in the prototype device,clarify the regulation rules of optical efficiency dependent on the concentration of doped quantum dots and device size,and calculate the optimal doping concentration and optimal optical efficiency.The model can also calculate the specific loss value of the device.According to simulation results,experimentally prepare LSCs based on quantum dots,which greatly improves the design and fabrication period of LSC.All-inorganic perovskite quantum dots are synthesized by the traditional hot injection method.High-performance all-inorganic perovskite quantum dot is used as the luminophor material and high-refractive index off-stoichiometry thiol-ene polymers is used as the photon transport to design and prepare the LSC.Perovskite quantum dots of different sizes and different optical properties are synthesized by changing the halide materials.The average particle diameter is less than 10 nm and the quantum yield is closed to 80%.The absorption coefficient is larger in the range of 400-600 nm and possessed larger stokes shift.When the concentration of Cs Pb Br₃perovskite quantum dots reaches 0.25 mg/m L and the geometric factor G=66.7,the optical efficiency of LSC is 4.75%.A hydrothermal decomposition method is used to synthesize carbon quantum dots.The precursor materials are rich and cheap while the synthesis method is simple.By controlling the reaction time,carbon quantum dots with different sizes and optical properties are synthesized.The synthesized carbon quantum dots have an average particle diameter of less than 10 nm,a large absorption coefficient in the visible light range,and a strong photoluminescence emission in the400-600 nm range.Carbon quantum dots are incorporated into off-stoichiometry thiol-ene polymers to prepare LSC.After testing,when the concentration of carbon quantum dots is 0.167mg/m L,the optical efficiency of LSC reaches 3.12%.After the LSC based on carbon quantum dot is irradiated for 12 hours under the condition of 260 sunlight,the performance of device remain above 95%,which shows the high photo-chemical stability.The near-infrared lead sulfide quantum dots are used to prepare LSC.Lead sulfide quantum dots have high quantum yields.The size and optical properties of quantum dots can be effectively tuned by controlling the reaction time.The particle diameter of the quantum dots is less than 10 nm.Under the excitation wavelength of 320 nm,lead sulfide quantum dots show strong photoluminescence emission in the 1100-1600 nm range.Lead sulfide quantum dots are incorporated into polymers to prepare LSC.After testing,the optical efficiency of LSC based on lead sulfide quantum dots reaches 2.9%.Meanwhile,an aluminum film with a thickness of 400 nm is plated on the back of the device by the method of thermal evaporation to achieve higher photon capture and effectively improve the optical efficiency of the LSC.