Browsing by Author "Ho, Dongil"

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BODIPY-Based Semiconducting Materials for Organic Bulk Heterojunction Photovoltaics and Thin-Film Transistors
(WILEY-V C H VERLAG GMBH, POSTFACH 101161, 69451 WEINHEIM, GERMANY, 2019) Ho, Dongil; Ozdemir, Resul; Kim, Hyungsug; Earmme, Taeshik; Usta, Hakan; Kim, Choongik; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü;
The rapid emergence of organic (opto)electronics as a promising alternative to conventional (opto)electronics has been achieved through the design and development of novel pi-conjugated systems. Among various semiconducting structural platforms, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) pi-systems have recently attracted attention for use in organic thin-films transistors (OTFTs) and organic photovoltaics (OPVs). This Review article provides an overview of the developments in the past 10 years on the structural design and synthesis of BODIPY-based organic semiconductors and their application in OTFT/OPV devices. The findings summarized and discussed here include the most recent breakthroughs in BODIPYs with record-high charge carrier mobilities and power conversion efficiencies (PCEs). The most up-to-date design rationales and discussions providing a strong understanding of structure-property-function relationships in BODIPY-based semiconductors are presented. Thus, this review is expected to inspire new research for future materials developments/applications in this family of molecules.
Microstructural modulation of organic passivation layers for metal oxide semiconductors to achieve high bias stability
(ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND, 2020) Ho, Dongil; Jeong, Ha-Yun; Minh Nhut Le; Usta, Hakan; Kwon, Hyuck-In; Kim, Myung-Gil; Kim, Choongik; 0000-0001-7494-0677; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
Electrical properties of metal oxide thin-film transistors (TFTs) are tunedviathe microstructural control of organic back-channel passivation layers. In this study, organic semiconductor (OSC) passivation layers with various molecular and physicochemical properties are employed to identify the back-channel passivation mechanism in solution-processed amorphous indium gallium zinc oxide (a-IGZO) TFTs. The OSC microstructure influences the passivation of electrical defects ina-IGZO TFTs by compensating for acceptor-like trap states and dangling bonds in the back-channel. First, the distance between an n-type OSC (C-60) and thea-IGZO back-channel is controlled by employing phosphonic acid molecules with different carbon chain lengths. Positive bias stress stability is tuned by applying both the OSC and carbon chain effect, leading to stable, high-performance TFTs with the determination of subgap density of states to confirm the compensation effects on the total acceptor-like defect states. The n-doping of identical passivation layers is further investigated by using perylenedicarboximide derivatives to confirm the proposed n-doping mechanism. Finally, the semiconductor 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene is selected on the basis of our proposed passivation model and exhibited good passivation characteristics. This study demonstrates an ideal molecular design for organic passivation layers, which shows significant potential for the realization of stable, high-performance TFTs.
A Solution-Processable meso-Phenyl-BODIPY-Based n-Channel Semiconductor with Enhanced Fluorescence Emission
(WILEY-V C H VERLAG GMBH, POSTFACH 101161, 69451 WEINHEIM, GERMANY, 2019) Ozcan, Emrah; Ozdemir, Mehmet; Ho, Dongil; Zorlu, Yunus; Ozdemir, Resul; Kim, Choongik; Usta, Hakan; Cosut, Bunyemin; 0000-0002-0618-1979; 0000-0002-7957-110X; 0000-0001-6530-0205; 0000-0001-6325-5674; 0000-0003-2811-1872; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
The cover feature shows the delicate balance between locally excited (LE) and twisted intramolecular charge-transfer (TICT) states, which could be controlled by solvent polarity and nano-aggregation, of a meso-phenyl-BODIPY-based fluorescent semiconductor. The dihedral angle between the meso-aromatic unit and BODIPY pi-core was found to be the key factor in this balance. This is the first report of highly emissive characteristics for an A-D-A type BODIPY-based n-channel semiconductor. Details are given in the Full Paper by B. Cosut, H. Usta, C. Kim, and co-workers (DOI: 10.1002/cplu.201900317).