The Study Of 1,3,6,8-tetrakis (Benzoic Acid) Pyrene Based Electrochromic Films And Devices

Electrochromism（EC）materials,as an emerging material,are mainly used in smart windows,anti-glare rearview mirrors and displays.The development of new EC materials has become a hot research topic in EC field in recent years.The energy level of 1,3,6,8-tetrakis（benzoic acid）pyrene（H₄TBAPy）molecule has a good match with the valence band/conductor band of TiO₂,and by finely tuning the energy level difference between the two,the EC performance can be controlled.The kinetic process of electron transfer in the EC films can be finely regulated to significantly enhance the EC performance of the complex films.The details of the study are as follows:1.A complete ECD（HOF//PT-ECD）was constructed using H₄TBAPy HOF as the working electrode and PW₁₂O₄₀^3--TiO₂（PT）transparent composite membrane as the counter electrode ionic liquid as the electrolyte.At the same applied voltage,the introduction of PT counter electrode reduces the working potential of ECD bleaching,which in turn reduces the overpotential of the working electrode and reduces the chance of H₄TBAPy stripping from the working electrode to form EC inert dimer.The bleaching potential of the optimized HOF//PT-ECD was reduced from-2.0 V to 0V compared with the ECD using FTO alone as the counter electrode（HOF-ECD）.Its optical contrast was improved from 20.1%to 67.5%,the bleaching and coloring response times were shortened from 16.8 s and 19.8 s to 5.1 s and 3.6 s,respectively,and the coloration efficiency was improved from 63.37 cm² C^-1 to 373.28 cm² C^-1.This study provides a new model and idea for the preparation of H₄TBAPy-based electrochromic devices.2.By introducing-NO₂ in H₄TBAPy,the energy level regulation of H₄TBAPy parent was achieved,and at the same time,TiO₂@H₄TBAPy and TiO₂@H₄TBAPy-NO₂ EC composite films were prepared.Since the LUMO of H₄TBAPy（-NO₂）is higher than the CB of TiO₂,H₄TBAPy（-NO₂）plays the role of electron blocking,which slows down the rate of rapid electron transfer from the coloring state TiO₂ to the electrolyte and thus the bleaching after power failure,and prolongs the coloring memory time of ECD.Compared with TiO₂ films,the optical contrast of TiO₂@H₄TBAPy and TiO₂@H₄TBAPy-NO₂ from 54.7%increased to85.6%and 80.4%;the memory time after coloring power-off was extended from1700 s to 2950 s and 3770 s.This study provides an effective way to prepare EC films with long power-off memory time and long cycle life.This study provides an effective way for the preparation of EC films with long power-off memory time and long cycle life.