Construction And Performance Of Electrochromic Smart Device Driven By CZTSSe Solar Cell

To achieve the strategic targets of"emission peak"and"carbon neutrality",it is imperative to develop low-carbon and energy-saving buildings.As a kind of green and environment friendly device that can reduce building energy consumption,electrochromic smart window has been very popular.It can change its optical properties by applying an external bias voltage to adjust the transmission of visible and near-infrared light indoor,offsetting up to 30%of the building’s energy consumption.But the requirement for an external electrical supply greatly limits their application in energy-saving buildings.The combination of photovoltaic technology and electrochromic technology can realize the true"zero energy consumption"self-driven electrochromic smart devices,which can dynamically adjust the indoor light and temperature according to the weather conditions to reduce the building’s energy consumption due to heating and cooling.It is of great significance to improve the energy saving level of modern buildings and reduce the consumption of fossil energy.However,the color and matching degree of electrochromic smart devices driven by solar cells are still a challenge.The construction of self-driven smart devices with neutral color and high matching degree is an important way to achieve high efficiency and low energy consumption buildings.In this thesis,we constructed a novel self-driven electrochromic multi-functional smart device by integrating a nickel-cobalt bimetal oxide（Ni Co O₂）-based electrochromic device with kesterite Cu₂Zn Sn（S,Se）₄（CZTSSe）thin-film solar cell and its performance was optimized.Benefiting from the neutral coloring characteristics of nickel（Ni）-based and cobalt（Co）-based oxides,the synergistic effect of Ni and Co elements,unique merits of CZTSSe solar cell and good compatibility with electrochromic device,the color and matching degree of self-driven smart devices are improved.The main work is divided into the following two parts:Design and construction of electrochromic smart device driven by CZTSSe solar cell:in this work,we design and construction a novel self-driven electrochromic smart device with neutral color and high matching degree by the combination of Ni Co O₂-based electrochromic device and CZTSSe solar cell,which realizes the functional integration of self-driven,electrochromic and energy storage.To solve the color problem,we successfully prepared Ni Co O₂electrochromic films with neutral coloring characteristics by the strategy of chemical bath deposition（CBD）,which can realize reversible switch between transparent and brown to improve the comfort of the residents.Specifically,the obtained Ni Co O₂electrochromic films display a large optical modulation（60.0%at 550 nm）,short switching time（7.6/11.4 s）,outstanding stability and excellent rate capability.The electrochromic energy-storage device（EESD）constructed based on the high performance Ni Co O₂thin film demonstrates excellent compatibility with CZTSSe solar cells.The self-driven EESD exhibits good electrochromic performance（optical modulation at 550 nm is 51.0%and coloring time is 17 s）,and can intelligently manage solar radiation by neutral color tinting according to light intensity.In addition,the smart device stores energy density up to 112.2 m Wh m^-2,which can be used as an energy storage device to power other electronic devices at night（such as LED）,realizing the collection,storage and utilization of energy.Study on the improvement of CZTSSe solar cell driven EESD performance by thioacetamide（TA） treatment:in the first part of our work,the low output power of the self-driven system limits the matching degree,switching performance and applications development of the smart devices.In this work,the surface of the absorber layer of CZTSSe solar cells is modified by TA sulfurization to increase the open circuit voltage(V_OC)and output power,which can improve the switching performance and the matching degree of CZTSSe solar cell driven EESD.TA low temperature vulcanization treatment can accurately control the incorporation amount of S,increase the band gap on the surface of the absorption layer and interact with the surface of the absorption layer to achieve the purpose of passivation surface defects,which can effectively reduce the interface recombination.Meanwhile,TA treatment can increase the width of the depletion region,which are more conducive to the light absorption and carrier extraction at the interface.In addition,the interfacial recombination activation energy is closer to the band gap,indicating that the interfacial recombination of the heterojunction is significantly inhibited.The V_OCof a single CZTSSe solar cell was improved from 451 m V to 493 m V,with the power conversion efficiency（PCE）increased from9.9%to 12.1%.The V_OCof the mini-module was increased from 3.1 V to 3.7 V compared to the mini-module without TA treatment.The output power density of the self-drive system was increased from14.3 m W cm^-2to 17.1 m W cm^-2by about 20%.The self-driven EESD after TA treatment exhibits a larger optical modulation range（53.0%at 550 nm）and a shorter coloring time（11.8 s）,resulting in better solar irradiation management performance and further improving in matching degree,which has a broad practical application prospect.