| Conjugated polymer materials possess the advantages of Non-toxic materials,flexible structure,simple preparation and low cost.They have applied in organic semiconductor optoelectronic devices such as light-emitting diodes,solar cells,etc.The performance of optoelectronic devices strongly dependent on the microstructures of polymer films.In recent years,people have focused on the research of regulating polymer chain behavior at the molecular level by controlling preparation methods.However,there are relatively few reports on the establishment of intrinsic relationships in the manufacturing process,molecular aggregation,exciton behavior,and the relationship between the microstructure(intra-molecular,inter-molecular,and methyl chains)of polymer films,crystal properties and electrical properties.These issues are key to understand the exciton behavior and the optoelectronic physical processes in optoelectronic devices.In order to solve these problems,we need to deeply understand the inherent relationships among the processing methods,morphological characteristics,exciton behavior,crystallization characteristics,and electrical characteristics of polymer films with different molecular aggregation regimes.We use a combination of optical microscopy,time-resolved spectroscopy,phase and crystal structure methods to systematically analyze the photophysical and electrical properties of organic semiconductor conjugated polymer poly(3-hexylthiophene-2,5-diyl)(P3HT),including the following aspects:(1)Explore the factors affecting the molecules aggregation of P3 HT thin film.We realized the H-type and J-type P3 HT thin film through controlling the processing methods.Then,we deeply focus on the effects of additives and solvent solidification rate on P3 HT phase separation,molecular chain alignment characteristics,and exciton coupling in H-and J-aggregate regimes.The experimental results show that,by doping the polar additive poly(ethylene oxide)(PEO)and reducing the solvent solidification rate,the degree of phase separation of P3 HT can be increased,and the ordering of the intrachain arrangement in P3 HT molecular can be enhanced in both H-aggregate(positive exciton coupling)and J-aggregate(negative exciton coupling).(2)Exciton coherence processing and dynamics of P3 HT in H-and J-aggregate regimes.The experimental results show that the P3 HT film in H-aggregate regimes is the weakly interchain coherence and the average life of the exciton is longer;the P3 HT film in J-aggregate regimes is the strongly intrachain coherence and the average life of the exciton is shorter.(3)Crystal characteristics and electrical characteristics of P3 HT films in H-and Jaggregate regimes.The experimental results show that the crystallinity in alkyl chain and the molecular arrangement are improved in J-type P3 HT film.It may facilitate the orderly improvement of P3 HT molecules in the π-π stacking direction,which leads to an increase in the Hall mobility of P3 HT films.(4)The interlink between the processing methods,molecular aggregation,exciton behavior,molecular chain and spatial arrangement of P3 HT films in H-and J-aggregate regimes.It found that in H-aggregates,the solvent solidification rate is faster during the film processing,denoting a weak interchain exciton coherence and a larger interchain free exciton bandwidth,thus the average lifetime of the exciton lives longer.Meanwhile,it is suggested the lower degree of order along the molecular chain,higher degree of order across the molecular chains and lower degree of order of the arrangement of the alkyl chains.In J-aggregates,the solvent solidification rate is slower during the film processing,denoting a strong intrachain exciton coherence and a smaller interchain free exciton bandwidth,thus the average lifetime of the exciton lives shorter.Meanwhile,it is suggested the higher degree of order along the molecular chain,lower degree of order across the molecular chains and higher degree of order of the arrangement of the alkyl chains. |
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