Light Catalytic Polymerization Preparation Of Poly (thiophene/tungsten Trioxide Composite Membrane And Its Photoelectric Conversion And Electrically Induced Discoloration Performance Research

Conjugated polymer/inorganic nanocomposites combine unique properties of polymers and inorganic nano-crystals and have been extensively studied as potential photovoltaic and electrochromic candidates. For photovoltaic and electrochromic application, the polymer-inorganic nano-composites are limited to only a few nano-semiconductor and conjugated polymer due to the restrictions of compounding technology. Most of the studies have used TiO2, ZnO and CdSe semiconductors to suite the electronic properties of P3HT, PPV, P3OT and their derivatives.WO3have been fully studied as inorganic electrochromic material and its various crystal types and nano-structure endue WO3with unique optical and electrical properties. Polythiophene has a stable electrochromic properties and high contrast, making it the most promising electrochromic polymer materials. For photovoltaic application, it is important that PT has the lowest unoccupied molecularorbital (LUMO) energy level higher than the WO3conduction band (CB) level, the energy difference makes possible the dissociation of photoexcited electron-hole pairs at the interface. Therefore, the PT-WO3hybrid material has great potential in electrochromic and photovoltaic field. PT intends to aggregate even in good solvents, making it difficult to obtain PT-WO3nanocomposites by traditional wet deposition methods. According to the authors’knowledge, there is no WO3and conjugated polymer composite material used for electrochromic devices and photovoltaic devices.In this work, a novel polythiophene-WO3hybrid film was prepared for photovoltaic and electrochromic application. Firstly, WO3nano-crystal film was prepared on ITO subtract, then PT-WO3hybrid film was synthesized via photo-catalytic polymerization. Photovoltaic devices and devices were assembled with the PT-WO3hybrid film, and the performances of both devices were exhaustively studied. The main findings are as follows:(1) Monoclinic WO3nano-crystal films were prepared using a sol-gel method and the films have good adhesion to the ITO substrate. It is the first time to photopolymerized thiophene initiated by WO3nano-crystal and also the first time to prepare the PT-WO3hybrid films via an in-situ polymerization. Raman results confirmed the hybrid film consisting of PT and monoclinic WO3, and the PT layer grows on the WO3substrate with reaction time. Polythiophene penetrated into the porous WO3substrate, and eventually a uniform PT-WO3hybrid film was obtained.(2) The results confirmed that existence of oxidized PT chains and reduced W(V). Part of sulfur sites of PT are bound with the tungsten atoms in the substrate, leading to an acceptor-donor complex. The electrons transferred from PT to WO3during the polymerization, forming a strong interaction between PT and WO3. ESR results confirmed that electrons transferred from PT to WO3, leading to stable charge separation at the interface. With UV excitation, the charge transfer process continued to proceed, and the rate of oxidized PT and reduced WO3raise.(3) Solar cells were fabricated by using PT-WO3hybrid films. Through optimizing the reaction conditions, a solar cell with good performance could be obtained. The IPCE curve shows both PT and WO3components are devoted to the light-harvesting.(4) Electrochromic devices were fabricated by using PT-WO3hybrid films as functional layer. Electrochromic devices with PT-WO3of different morphologies were fabricated and evaluated. The influence of electrolyte and counter electrode were also studied. The optimal device structure:porous PT-WO3films as the EC layer, LiClO4/N(C4H9)ClO4dispersed in PMMA as solid electrolyte, NiO as counter electrode.(5) The optimized electrochromic device has a good performace:contrast of62%(at700nm), the response time of1.5s, and coloration efficiency of212.6cm2/C. The device has a stable performance after multiple cycle tests.