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RISS 인기검색어
- 검색키워드
- 저자 : Zhengran He (검색결과 5 건)
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Crystal growth of small-molecule organic semiconductors with nucleation additive
He Zhengran,Zhang Ziyang,Asare-Yeboah Kyeiwaa,Bi Sheng,Chen Jihua,Li Dawen 한국물리학회 2021 Current Applied Physics Vol.21 No.-
In this study, we employ a nucleation additive 4-octylbenzoic acid (OBA) with an optimized solvent evaporation method to regulate crystal orientation and grain width of small-molecule organic semiconductors. When 6,13-bis (triisopropylsilylethynyl) pentacene (TIPS pentacene) was utilized as a benchmark material to mix with the additive, a self-assembled OBA interfacial layer was formed and promoted uniform deposition of nucleation seeds. As a result, the TIPS pentacene/OBA blend crystalline film exhibited crystal alignment in long range order, attributing to a 11-fold reduction of the crystal misorientation angle and a 4-fold increase of the grain width. We further discussed the important correlation between the effective hole mobility, grain boundaries, grain width and length, and nucleation sites. Organic thin film transistors were fabricated to test charge transport, yielding a hole mobility of up to 0.17 cm2/V. This work provides a new pathway to modulate the nucleation and crystallization events of organic semiconductors, and can potentially be applied to optimize the thin film morphology and electrical performance of organic semiconducting materials in general.
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Zhengran He,Ziyang Zhang,Sheng Bi,Jihua Chen 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.5
The utilization of polymer additives provides an intriguing pathway to tune the electrical performance of solution-grown,small-molecular organic semiconductors. In this study, we report the effect of different polymer molecular weight on thecrystal growth, phase segregation and charge transport of the organic semiconductors. A semicrystalline polymer additivepolyethylene oxide (PEO) with 8000 and 100 K molecular weight was blended with a well-known organic semiconductor6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene). Distinctively different thin film morphology of the resultantTIPS pentacene/PEO blend film was identified and quantitatively characterized. In particular, PEO with a higher molecularweight of 100 K exerted a stronger effect on enhancing film formation, crystal coverage and likely mechanical properties,whereas PEO with an 8000 molecular weight yielded more superior crystal alignment and larger crystal sizes. Bottom-gate,top-contact TIPS pentacene/PEO OTFTs were fabricated to test the charge transport, which indicated loading the PEOpolymer with molecular weight of 8000 demonstrated a five-fold enhancement in the extracted hole mobilities as comparedto the 100 K counterpart. This work of using polymer additives with different molecular weight can be used to tune thecrystallization of other solution-processed high-mobility small-molecular organic semiconductors.
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Solvent Exchange in Controlling Semiconductor Morphology
Zhengran He,Ziyang Zhang,Kyeiwaa Asare-Yeboah,Sheng Bi 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.6
Recent studies in solution processed, small molecular organic semiconductors have reported unparalleled advances in charge carrier mobilities, warranting promising application in organic electronic devices such as organic gas sensors and complimentary circuits. However, the in-solution crystallization of small molecular organic semiconductors has presented specific challenges including crystal misorientation, grain boundary and mobility variation. In this article, we first discuss the effects of these issues on charge transport and highlight the virtues of solvent choices to optimize the semiconductor morphology. Then, we conduct an in-depth review of the miscellaneous solvent exchange methods to effectively palliate these challenges. By discussing various benchmark semiconductor materials such as 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) and perylenetetracarboxyldiimide derivatives (PTCDI-Cn), we demonstrate the solvent exchange-based crystallization methods can modulate supramolecular aggregation, promote nucleation formation, improve semiconductor alignment, change crystal dimensionality, and enhance charge transport. We believe this work provides useful comprehension of employing the solvent exchange methods to powerfully regulate the crystallization, morphology and mobility of organic semiconductors, and thereby casts light on high performance organic electronic applications.
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A Lightweight Pedestrian Intrusion Detection and Warning Method for Intelligent Traffic Security
Xinyun Yan,Zhengran He,Youxiang Huang,Xiaohu Xu,Jie Wang,Xiaofeng Zhou,Chishe Wang,Zhiyi Lu 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.12
As a research hotspot, pedestrian detection has a wide range of applications in the field of computer vision in recent years. However, current pedestrian detection methods have problems such as insufficient detection accuracy and large models that are not suitable for large-scale deployment. In view of these problems mentioned above, a lightweight pedestrian detection and early warning method using a new model called you only look once (Yolov5) is proposed in this paper, which utilizing advantages of Yolov5s model to achieve accurate and fast pedestrian recognition. In addition, this paper also optimizes the loss function of the batch normalization (BN) layer. After sparsification, pruning and fine-tuning, got a lot of optimization, the size of the model on the edge of the computing power is lower equipment can be deployed. Finally, from the experimental data presented in this paper, under the training of the road pedestrian dataset that we collected and processed independently, the Yolov5s model has certain advantages in terms of precision and other indicators compared with traditional single shot multiBox detector (SSD) model and fast region-convolutional neural network (Fast R-CNN) model. After pruning and lightweight, the size of training model is greatly reduced without a significant reduction in accuracy, and the final precision reaches 87%, while the model size is reduced to 7,723 KB.
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Yeqing Sun,Ziyang Zhang,Kyeiwaa Asare‑Yeboah,Sheng Bi,Zhengran He 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.1
Despite solution processed organic semiconductors have attracted much research attention, the randomized crystallizationand large prevalence of grain boundary remain as a challenge to realize high performance organic electronic applications. In this work, we report the incorporation of poly(butyl acrylate) polymer additive with organic semiconductors with themediation of a solvent vapor annealing method in order to modify the nucleation and crystal growth process. As 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was experimented as a benchmark semiconductor, we demonstratedthat the TIPS pentacene/poly(butyl acrylate) mixture exhibits rigidly aligned crystals, large grain width and improved arealcoverage. In particular, thin film morphological characterization indicated a substantial reduction in misorientation angle byapproximately two orders of magnitude as well as a 5-fold enlargement of grain width. A grain boundary model is proposedas a theoretic basis to understand the connection between grain width and hole mobility. Bottom-gate, top-contact thin filmtransistors based on TIPS pentacene/poly(butyl acrylate) blends demonstrated enhanced hole mobility of up to 0.11 cm2/Vs.
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