Preparation Of Electrochromic Materials Based On Triphenylamine,and Studying On Devices With High Optical Contrast

Under an applied electric field,the optical properties?reflectance,absorptivity,transmittance,etc.?of the electrochromic materials can be reversibly changed,which visually manifests as a change in color.Electrochromic devices have broad application prospects in the fields of electrochromic smart windows,automotive anti-glare rearview mirrors and displays.Under electrochemical oxidation conditions,triphenylamine derivatives easily lose electrons to form stable cationic radicals,accompanied by significant color changes.Thus,electrochromic materials based on triphenylamine derivatives have attracted people's attention.In this thesis,the authors synthesized and prepared a series of organic conjugated triphenylamine derivatives and their corresponding polymers.The molecular structures of the target compounds were characterized and confirmed by mass spectrometry?MS?,nuclear magnetic resonance spectroscopy?NMR?and fourier transform infrared spectroscopy?FTIR?.The molecular structures of the compounds are as follows:The basic photoelectric and electrochromic properties of triphenylamine derivatives and their corresponding polymers were investigated by UV-vis spectrometer,electrochemical workstation and electrochromic cycle tester.Meanwhile,cross-linked poy?4-vinyltriphenylamine?of different thickness?PVTPA-CLn,n=1,2,3?films?or N,N,N',N'-tetraphenylbenzidine?TPB?and its derivatives?and ethyl viologen(EV²⁺·2PF₆^?)?or tungsten oxide?WO₃??were used as anodic and cathodic electrochromic materials,respectively;they were assembled into bipolar color complementary electrochromic devices?ECDs?.The electrochromic properties of ECDs were investigated by UV-Vis spectrometer,electrochemical workstation and electrochromic cycle tester.The results showed that the PVTPA-CLn films exhibited better cycle stability compared to PVTPA film,which had certain guiding significance for preparing materials and devices with good electrochromic cycle stability.It also been found that PVTPA-CL2?or TPB and its derivatives?could be assembled with EV²⁺·2PF₆^??or WO₃?into a variety of bipolar color-complementary electrochromic devices.These devices exhibited reversible color change between the bleached state with high optical transmittance and black color,and their maximum optical contrast were greater than 75.7%,which was of great significance for further development of black electrochromic devices with high optical contrast.The specific research contents of this thesis include the following four sections:In section 1:A series of triphenylamine derivatives,TPA-CHO,TPA-E2CN,TPA-2T-CHO,TPA-2T-E2CN,TPA-2EDOT-CHO and TPA-2EDOT-E2CN was synthesized,and their photoelectric properties were investigated.The polymer films based on triphenylamine derivatives?P?TPA-2T-CHO?,P?TPA-2T-E2CN?,P?TPA-2T-E2CN??were deposited on transparent conductive glass?ITO glass?by electrochemical polymerization.The electrochromic properties of polymer films were investigated.It was found that the polymer films exhibited a reversible color change upon applying voltage.The polymer films exhibited high optical contrast in visible and near-infrared regions,and their optical contrast were81.8%,41.4%,65.8%,and 75.6%at 1000 nm,respectively.Polymers containing3,4-ethylenedioxythiophene?EDOT?groups exhibited a lower electrochromic driving voltage and better electrochromic cyclic stability compared to polymers containing thiophene groups.The electrochromic driving voltage of the P?TPA-2EDOT-CHO?and P?TPA-2EDOT-E2CN?films was+1.5 V.In section 2:Poly?4-vinyltriphenylamine??PVTPA?and cross-linked poly?4-vinyltriphenylamine?of different thickness?PVTPA-CLn,n=1,2,3?films were prepared.Their photoelectric and electrochromic properties were investigated.The ECD 1?device structure:ITO glass/PVTPA-CL2 film/gel electrolyte I/ITO glass?and ECD 2?device structure:ITO glass/PVTPA-CL3 film/gel electrolyte I/ITO glass?were assembled using PVTPA-CL2 and PVTPA-CL3 films as electrochromic layer,respectively;and their electrochromic properties were investigated.It was found that PVTPA-CLn films exhibited higher electrochromic cyclic stability and higher optical contrast than PVTPA film.The PVTPA-CL2 and its electrochromic device ECD 1 exhibited reversibly color change between colorless and grayish green.The PVTPA-CL3 and its electrochromic device ECD 2 exhibited reversibly color change between colorless and black.The optical contrast of ECD 1 and ECD2 were 81.0%and 84.3%at 750 nm,respectively.In addition,the optical contrast of ECD 2was greater than 58.3%in the entire visible light region.In section 3:TPB and its derivatives?TPB,TPB-2CHO and TPB-4Me?were synthesized,and their photoelectric properties were investigated.ECD 3?device structure:ITO glass/gel electrolyte II+TPB/ITO glass?and ECD 4?device structure:ITO glass/gel electrolyte II+TPB-2CHO/ITO glass?and ECD 5?device structure:ITO glass/gel electrolyte II+TPB-4Me/ITO glass?were assembled using TPB,TPB-2CHO and TPB-4Me as active materials,respectively.Their electrochromic properties were investigated.ECD 3 based on TPB can undergo reversibly color change between colorless and orange when a voltage was applied;ECD 4 based on TPB-2CHO can undergo reversibly color change between light yellow and orange when a voltage was applied;and ECD 5 based on TPB-4Me can undergo reversibly color change between colorless and grayish green when a voltage was applied.The maximum optical contrasts of ECD 3,ECD 4,and ECD 5 were 89.2%?480 nm?,58.3%?500nm?,and 90.3%?480 nm?,respectively.In section 4:The EV²⁺·2PF₆^?and WO₃ films were synthesized and prepared,respectively.Their electrochromic properties were investigated.Eight bipolar electrochromic devices were assembled using EV²⁺·2PF₆^??or WO₃?and PVTPA-CL2 film?or TPB and its derivatives?as electrochromic materials:ECD 8?device structure:ITO glass/PVTPA-CL2film/ethyl viologen gel electrolyte I/ITO glass?,ECD 9?device structure:ITO glass/PVTPA-CL2 film/gel electrolyte I/WO₃ film/ITO glass?,ECD 10?device structure:ITO glass/ethyl viologen gel electrolyte II+TPB/ITO glass?),ECD 11?device structure:ITO glass/ethyl viologen gel electrolyte II+TPB-2CHO/ITO glass?,ECD 12?device structure:ITO glass/ethyl viologen gel electrolyte II+TPB-4Me/ITO glass?,ECD 13?device structure:ITO glass/gel electrolyte II+TPB/WO₃ film/ITO glass?,ECD 14?device structure:ITO glass/gel electrolyte II+TPB-2CHO/WO₃ film/ITO glass?,ECD 15?device structure:ITO glass/gel electrolyte II+TPB-4Me/WO₃ film/ITO glass?.The electrochromic properties of ECDs were investigated.It was found that EV²⁺·2PF₆^??or WO₃?and PVTPA-CL2 films?or TPB and its derivatives?were complementary color electrochromic materials.It was also found that both ECD 8 and ECD 9 exhibited a reversible color change between colorless and black.The optical contrast of ECD 9 was not less than 73.2%in the range of 440-960 nm.ECD 8 and ECD 9 exhibited lower electrochromic driving voltage,higher optical contrast,and longer cyclic stability than the colorless to black electrochromic device ECD 2 based on PVTPA-CL3 film?in section 2?.The electrochromic driving voltages of ECD 8 and ECD 9were+1.5 V and+2.0 V,respectively.Meanwhile,it was also found that the bipolar electrochromic devices ECD 10,ECD 11,ECD 12,ECD 13,ECD 14,and ECD 15 exhibited reversibly change color between the bleached state with high optical transmittance and black.Their optical contrasts were 78.6%,69.5%,87.6%,87.2%,83.0%,and 75.7%at 700 nm,respectively.In addition,ECD 10,ECD 11,and ECD 12 still maintain good electrochromic properties after 800 times electrochromic cycles.