https://scholar.dgist.ac.kr/handle/20.500.11750/4361 2026-04-22T07:40:10Z https://scholar.dgist.ac.kr/handle/20.500.11750/12824 Title: Design and Synthesis of a New Non-Fullerene Acceptor for High-Performance Photomultiplication-Type Organic Photodiodes Author(s): Sim, Hye Ryun; Kang, Mingyun; Yu, Seong Hoon; Nam, Geon-Hee; Lim, Bogyu; Chung, Dae Sung Abstract: Photomultiplication-type organic photodiodes (PM-OPDs) rely on acceptor molecules for both charge separation and efficient gain generation. Herein, a new non-fullerene acceptor is designed and synthesized by introducing thienylenevinylene (TV) groups into the conventional 2,2MODIFIER LETTER PRIME-[[6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2MODIFIER LETTER PRIME,3MODIFIER LETTER PRIME-dMODIFIER LETTER PRIME]-s-indaceno[1,2-b:5,6-bMODIFIER LETTER PRIME]dithiophene-2,8-diyl]bis[methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinitrile] (ITIC) structure. The resulting TV-ITIC acceptor possesses not only extended pi-conjugation length, which leads to lower energy bandgap as well as deeper lowest unoccupied molecular orbital (LUMO) level, but also enhanced hydrophobic characteristics, owing to the increased volumetric portion of the aliphatic chain, which improves the miscibility with the donor polymer semiconductor, poly(3-hexylthiophene-2,5-diyl) (P3HT). Moreover, pristine TV-ITIC films consist of intrinsically well-ordered anisotropic crystallites, which are confirmed by 2D grazing incidence X-ray diffraction (2D-GIXD) analysis. All of these photophysical properties are beneficial for efficient exciton separation, electron trapping, and charge injection abilities of PM-OPDs compared to those obtained with conventional ITIC. Because of such synergetic contributions of TV-ITIC to the photomultiplication mechanism, the resulting optimized PM-OPD exhibits a high external quantum efficiency (>74,000%) and a large specific detectivity (>10(12) Jones). © 2020 Wiley-VCH GmbH 2021-01-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/12814 Title: Thermoelectric power factor exceeding 50 mu W m(-1)K(-2)from water-borne colloids of polymer semiconductors Author(s): Nam, Gwang Hui; Ha, Jae Un; Chung, Dae Sung Abstract: An environmentally benign process for the fabrication of polymer thermoelectrics is proposed based on a miniemulsion synthesis for transferring polymer semiconductors dissolved in organic solvents to aqueous media with surfactants. Considering that the particle size of the colloid and concentration of the surfactant micelles can affect the final morphology of films cast from the colloidal solution, the dialysis time for extraction of the surfactant from the colloidal solution was systematically varied to achieve poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C-14) colloidal films with diverse morphologies. Morphological and structural analyses indicated that a longer dialysis time produced a larger particle size owing to Ostwald ripening, in addition to a lower interparticle depletion force as a result of the reduced amount of surfactant micelles. These competing phenomena in the colloidal solutions prior to solidification yielded smoother and more continuous film morphologies as the dialysis time increased. Interestingly, although the charge carrier mobility and electrical conductivity gradually increased with the dialysis time as the film morphology became smoother, however, the Seebeck coefficient tended to increase as the crystalline disorder increased presumably because of the broadened density of states. The resulting organic thermoelectrics with the optimized film morphology rendered a high Seebeck coefficient of 495.96 mu V K(-1)and power factor of up to 54.89 mu W m(-1)K(-2). This approach opens the possibility of fabricating high-performance organic thermoelectrics with water as a processing solvent. This journal is © The Royal Society of Chemistry. 2020-09-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/11539 Title: Synthesis of Cyclopentadithiophene-Diketopyrrolopyrrole Donor-Acceptor Copolymers for High-Performance Nonvolatile Floating Gate Memory Transistors with Long Retention Time Author(s): Jeon, Soyeon; Sun, Cheng; Yu, Seong Hoon; Kwon, Soon-Ki; Chung, Dae Sung; Jeong, Yong Jin; Kim, Yun-Hi Abstract: Organic flash memories that employ solution-processed polymer semiconductors preferentially require internal stability of their active channel layers. In this paper, a series of new donor-acceptor copolymers based on cyclopentadithiophene (CDT) and diketopyrrolopyrrole (DPP) are synthesized to obtain high performance and operational stability of nonvolatile floating-gate memory transistors with various additional donor units including thiophene, thiophene-vinylene-thiophene (CDT-DPP-TVT), selenophene, and selenophene-vinylene-selenophene. Detailed analyses on the photophysical, two-dimensional grazing incident X-ray diffraction, and bias stress stability are discussed, which reveal that the CDT-DPP-TVT exhibits excellent bias stress stability over 105 s. To utilize the robust nature of CDT-DPP-TVT, floating-gate transistors are fabricated by embedding Au nanoparticles between Cytop layers as a charge storage site. The resulting memory devices reveal bistable current states with high on/off current ratio larger than 104 and each state can be distinguished for more than 1 year, indicating a long retention time. Moreover, repetitive writing-reading-erasing-reading test clearly supports the reproducible memory operation with reversible and reliable electrical responses. All these results suggest that the internal stability of CDT-DPP-TVT makes this copolymer a promising material for application in reliable organic flash memory. Copyright © 2019 American Chemical Society. 2019-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/11394 Title: Surfactant-Induced Solubility Control to Realize Water-Processed High-Precision Patterning of Polymeric Semiconductors for Full Color Organic Image Sensor Author(s): Sim, Kyu Min; Yoon, Seongwon; Kim, Soo-Kwan; Ko, Hyunki; Hassan, Syed Zahid; Chung, Dae Sung Abstract: A fully water-based patterning method for polymer semiconductors was developed and utilized to realize high-precision lateral patterning of various polymers. Water-borne polymer colloids, wherein hydrophobic polymers are dispersed in water with the assistance of surfactant molecules, possess a hydrophilic surface when printed onto a substrate. When this surface is exposed to a washing molecule, the surface of the polymer film recovers its original hydrophobic nature. Such surfactant-induced solubility control (SISC) enables environmentally benign, water-processed, and high-precision patterning of various polymer semiconductors with totally different solubilities, so that fully water-processed polymer organic image sensors (OISs) can be realized. B-/G-/R-selective photodiodes with a pixel size of 100 μm × 100 μm were fabricated and patterned by this water-based SISC method, leading to not only high average specific detectivity values (over 1012 Jones) but also narrow pixel-to-pixel deviation. Thanks to the superiority of the SISC method, we demonstrate the image capturing ability of OISs without B-/G-/R-color filters, from a fully water-based fabrication process. © 2019 American Chemical Society. 2019-12-31T15:00:00Z