Design Of Donor-Acceptor Based Organic Molecules And Research On Their Optical And Electrical Properties

Donor-Acceptor（D-A）organic molecules are widely developed and used in fields such as fluorescent molecular probes,electrochemiluminescence,and solar cells due to their clear structure,ease preparation,functionalization,and low synthesis costs.Selecting appropriate functionalized organic donor and acceptor molecules for different needs can effectively improve optical and electrical properties,obtain higher energy conversion efficiency,and effectively utilize their applications in optical,catalytic,and optoelectronic devices.Therefore,we have designed and synthesized donor-acceptor organic molecules based on charge transfer,and applied these compounds to the fields of electrochemiluminescence（ECL）and photoelectric conversion,effectively enhancing optical and electrical properties.In addition,the interface electron transfer kinetics of donor-acceptor organic molecules and their composite materials were deeply explored through the UV-vis/SECM（Scanning Electrochemical Microscope,SECM）platform,and the internal electron transfer and charge separation efficiency of the system were studied,providing more powerful theoretical verification support for experimental conclusions.The main research contents of this paper are as follows:1.Donor-Acceptor type porphyrin-coumarin molecules to enhance electrochemical luminescence performancePorphyrin molecules are usually used as electron donors in molecules.By integrating two units,porphyrin and coumarin,into Schiff base reaction,porphyrin-coumarin（A-C）functional molecule with D-A is synthesized.Compared to monoaminoporphyrin（ATPP）,the ECL signal of A-C is nearly three times higher,overcoming the difficulty of porphyrin derivatives being prone to aggregation and quenching in the aqueous phase.At the same time,A-C is applied to detect copper ions in the aqueous phase,with a detection range of 10-385 n M and a detection limit of 0.64n M.Among them,the mechanism of electrochemical signal enhancement has been strongly verified through DFT theoretical calculations,demonstrating that the reason for the enhancement of A-C signal is the rapid transfer of donor electrons within the molecule to the acceptor,which increases the amount of sulfate anions in the electrochemiluminescence system,thereby obtaining more porphyrin-coumarin excited states and emitting stronger ECL.This part of work provides a smart idea for designing porphyrin molecules with strong electrochemical signals,and also provides a comprehensive explanation for studying the electrochemiluminescence mechanism of porphyrin derivatives.2.Imidazole organic molecules with donor-acceptor structure for efficient electron transferIn this chapter,three kinds of imidazole organic semiconductors with donor-acceptor electronic structure were synthesized,which enhanced the electron transfer performance.The specific adjustment methods are as follows:（1）Adjust the electron density of N in position 1 and N in position 3 by adjusting the electronic properties of the substituent in position 2 of imidazolyl-MI（donor）to achieve the purpose of adjusting its photoelectric properties;（2）Cyanovinyl（C≡N）has electron withdrawing properties and can induce intramolecular charge transfer of electrons from donor to acceptor groups under light irradiation;（3）To avoidπ-πaggregation of molecules,a non coplanar tetraphenylethylene（TPE）structure was introduced as acceptor to obtain excellent organic semiconductor materials with high photocurrent response.Photochemical measurements have shown that the photocurrent is significantly enhanced after the molecule is designed as donor-acceptor（D-A）.Compared to TPE-MI-NO₂ and TPE-MI-H,TPE-MI-OH（dual donor-acceptor）molecules have the best photoelectric performance.Combining SPECM and IMPS technology,it has been demonstrated that TPE-MI-OH has a faster rate of photoexcited electron transfer.This part of work proves that reasonably constructing donor-acceptor（D-A）organic semiconductors is an effective strategy to improve exciton separation efficiency,and dual donor-acceptor molecules can achieve better photoelectric performance.3.Enhanced electron transfer performance of triphenylamine organic semiconductors with dual donor-acceptor characteristicsTriphenylamine（TPA）has strong ability to supply electrons.It connects different numbers of triphenylamine molecules with the electron withdrawing group phenanthrimidazole（PI）to form a molecular structure with donor-acceptor（PI-1TPA）and double donor-acceptor（PI-2TPA）,which improves the intramolecular push-pull properties,thus regulating its photoelectric properties.By comparison,it was found that PI-2TPA with two triphenylamine molecules connected has a better photocurrent density.The main reason is that the LUMO energy level of PI-2TPA has a higher compatibility with the work function of conductive glass（FTO）.Meanwhile,due to its two triphenylamines,it increases the electron transport path,and the synergistic effect of the two makes PI-2TPA have the best photoelectric performance.The use of SPECM to verify that this dual donor molecule with multi-channel electron transport routes is conducive to rapid interfacial electron transfer and suppresses electron-hole recombination,proving the feasibility of this strategy.