Design And Preparation Of New Organic Dyes For Dye Sensitized Solar Cell

The speed-up in urbanization consumes a large amount of energy to meet the needs of society,causing sharply increased energy demand on this planet,hence provoking the crazy persuit of new and clean energy sources.Dye sensitized solar cell?DSSC?is one of the most promising clean energy sources,in which dye is one essential component.This study focuses on the design and synthesis of new organic dyes for DSSC,including the following parts:First,six organic dyes with carbazole as donor,phenothiazine?PTZ?as?-bridge and cyanoacrylate as acceptor were designed and synthesized.The design is such that the PTZ unit in three of them was connected to ethyl group?CBPTZ-n2?,while that in the others was connected to2-ethylhexyl group?CBPTZ-b8?.Furthermore,a phenyl group was inserted between the carbazole donor and the PTZ?-bridge to enable different bonding modes in these molecules?o/m/pCBPTZ?.Gaussian computation demonstrated the validity of our molecular design,e.g.,the energy levels as well as the distribution of electrons in the frontier orbitals,and the absorption spectra were all proved suitable for DSSC application.By photophysical and electrochemical studies,it was found that these dyes have high absorption intensity,wide absorption range and matched energy levels with redox potential of I^-/I₃^-,and with conduction band of titanium dioxide?TiO₂?.Second,the preparation and performance optimization of DSSC devices based on these six new dyes were conducted.Focusing dye of mCBPTZ-n2 and oCBPTZ-b8,respectively,the effects of dye soaking temperature and soaking solvent,as well as photoanode thickness on the performance of DSSC devices were firstly investigated to optimize the preparation conditions.Then,the six dyes were applied to DSSC device parallely for comparision by measuring both the density-photovoltage?J-V?curves and the monochromic incident photon-to-current conversion efficiency?IPCE?curves.It was found that among them,the mCBPTZ-n2 based devices exhibit the best photoelectric conversion efficiency?PCE?of 8.76%.Third,the influence of molecular structure on device performance was investigated.By measuring the adsorption capacity of each dye,the time-resolved photoluminescence spectrum?TRPL?of dye film,as well as the open circuit voltage decay?OCVD?and electrochemical impedance spectroscopy?EIS?of devices based on each dye,the effects of different connection modes between donors and?-bridges and different alkyl chains on the property of material and the performance of the DSSC devices were studied.Our research shows that in a dye containing any inert alkyl chain,changing the connection mode can adjust the corresponding torsion angle,which affects the intramolecular charge transfer?ICT?process of the dye,hence resulting in different device performance.At the same time,we find that the use of long branched alkyl chain instead of straight chain can more effectively prevent dye aggregation,while short-chain alkyl groups can increase the adsorption capacity of dyes on TiO₂,thus producing larger short-circuit current density(J_SC)in DSSC devices.