Organic Phototransistors: High‐Performance Phototransistors Based on Single‐Crystalline n‐Channel Organic Nanowires and Photogenerated Charge‐Carrier Behaviors (Adv. Funct. Mater. 5/2013)

Yu, Hojeong,Bao, Zhenan,Oh, Joon Hak WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.5

<P>On page 629, Hojeong Yu, Zhenan Bao, and Joon Hak Oh report single‐crystalline nanowire organic phototransistors (NW‐OPTs) fabricated using an n‐channel organic semiconductor, <I>N</I>,<I>N</I>′‐bis(2‐phenylethyl)‐perylene‐3,4:9,10‐tetracarboxylic diimide. Highly sensitive and reproducible photoresponses are observed from the NW‐OPTs and photogenerated charge carrier behavior is quantitatively investigated. The findings highlight single‐crystalline NW‐OPTs as an alternative to conventional thin‐film‐type photodiodes and could pave the way for optoelectronic device miniaturization. </P>

Highly-sensitive solution-processed 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TESADT) phototransistors for optical sensing applications

Kim, J.,Cho, S.,Kim, Y.H.,Park, S.K. Elsevier Science 2014 Organic electronics Vol.15 No.9

A highly-sensitive organic phototransistor, based on solution-processed 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TESADT) was fabricated and investigated for an optical sensing element. The phototransistor based on thin crystalline grains of diF-TESADT exhibited a significant threshold voltage (V<SUB>TH</SUB>) shift under a white light illumination in which the response time was estimated to be <0.5s and a current modulation greater than 10<SUP>6</SUP>. It was found that the V<SUB>TH</SUB> shift can be further enlarged by an additional gate bias, achieving very high light responsivity >10<SUP>3</SUP>A/W at 0.17mW/cm<SUP>2</SUP> and I<SUB>PH</SUB>/I<SUB>DARK</SUB> ratio higher than 10<SUP>6</SUP>. Also, by applying an erase gate bias, fast recovering of V<SUB>TH</SUB> to the initial position was possible. This phenomenon can be ascribed to the trapping and de-trapping of photo-generated carriers at the organic channel/dielectric interface, while the amount of trapped carriers can be also modulated simultaneously by the gate bias. This investigation identifies that the solution-processed diF-TESADT phototransistors can be used for large-area and low-cost optical sensors and memory applications. In particular, it can be claimed that performance improvement by a gate bias represents a universal method applicable to the organic phototransistors.

Light Sensing in a Photoresponsive, Organic-Based Complementary Inverter

Kim, Sungyoung,Lim, Taehoon,Sim, Kyoseung,Kim, Hyojoong,Choi, Youngill,Park, Keechan,Pyo, Seungmoon American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.5

<P>A photoresponsive organic complementary inverter was fabricated and its light sensing characteristics was studied. An organic circuit was fabricated by integrating <I>p</I>-channel pentacene and <I>n</I>-channel copper hexadecafluorophthalocyanine (F16CuPc) organic thin-film transistors (OTFTs) with a polymeric gate dielectric. The F16CuPc OTFT showed typical <I>n</I>-type characteristics and a strong photoresponse under illumination. Whereas under illumination, the pentacene OTFT showed a relatively weak photoresponse with typical p-type characteristics. The characteristics of the organic electro-optical circuit could be controlled by the incident light intensity, a gate bias, or both. The logic threshold (<I>V</I><SUB>M</SUB>, when <I>V</I><SUB>IN</SUB> = <I>V</I><SUB>OUT</SUB>) was reduced from 28.6 V without illumination to 19.9 V at 6.94 mW/cm<SUP>2</SUP>. By using solely optical or a combination of optical and electrical pulse signals, light sensing was demonstrated in this type of organic circuit, suggesting that the circuit can be potentially used in various optoelectronic applications, including optical sensors, photodetectors and electro-optical transceivers.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-5/am101284m/production/images/medium/am-2010-01284m_0005.gif'></P>

Hybrid Phototransistors Based on Bulk Heterojunction Films of Poly(3-hexylthiophene) and Zinc Oxide Nanoparticle

Nam, Sungho,Seo, Jooyeok,Park, Soohyeong,Lee, Sooyong,Jeong, Jaehoon,Lee, Hyena,Kim, Hwajeong,Kim, Youngkyoo American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.4

<P>Hybrid phototransistors (HPTRs) were fabricated on glass substrates using organic/inorganic hybrid bulk heterojunction films of p-type poly(3-hexylthiophene) (P3HT) and n-type zinc oxide nanoparticles (ZnO<SUB><I>NP</I></SUB>). The content of ZnO<SUB><I>NP</I></SUB> was varied up to 50 wt % in order to understand the composition effect of ZnO<SUB><I>NP</I></SUB> on the performance of HPTRs. The morphology and nanostructure of the P3HT:ZnO<SUB><I>NP</I></SUB> films was examined by employing high resolution electron microscopes and synchrotron radiation grazing angle X-ray diffraction system. The incident light intensity (<I>P</I><SUB>IN</SUB>) was varied up to 43.6 μW/cm<SUP>2</SUP>, whereas three major wavelengths (525 nm, 555 nm, 605 nm) corresponded to the optical absorption of P3HT were applied. Results showed that the present HPTRs showed typical p-type transistor performance even though the n-type ZnO<SUB><I>NP</I></SUB> content increased up to 50 wt %. The highest transistor performance was obtained at 50 wt %, whereas the lowest performance was measured at 23 wt % because of the immature bulk heterojunction morphology. The drain current (<I>I</I><SUB>D</SUB>) was proportionally increased with <I>P</I><SUB>IN</SUB> due to the photocurrent generation in addition to the field-effect current. The highest apparent and corrected responsivities (<I>R</I><SUB>A</SUB> = 4.7 A/W and <I>R</I><SUB>C</SUB> = 2.07 A/W) were achieved for the HPTR with the P3HT:ZnO<SUB><I>NP</I></SUB> film (50 wt % ZnO<SUB><I>NP</I></SUB>) at <I>P</I><SUB>IN</SUB> = 0.27 μW/cm<SUP>2</SUP> (555 nm).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-4/am302765a/production/images/medium/am-2012-02765a_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am302765a'>ACS Electronic Supporting Info</A></P>

Single-crystalline organic nanowire-gold nanorods hybrid nanomaterials for enhanced opto-electronic performance

정지형,윤민지,김동하,오준학 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Hybrid nanostructures may improve the properties or make up for the weakness of each material by assembling two materials into one system. Herein, opto-electronic performances of phototransistor based on gold nanorods (Au NRs)-decorated n-channel organic semiconductor, N,N'-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI) nanowire (NW) are reported. With the aid of excellent photoelectrical characteristics of BPE-PTCDI NW and localized surface plasmons in Au NRs, the hybrid system enhances responsivity, photocurrent ratio, and external quantum efficiency (EQE) under monochromatic light illumination comparing with those of bare BPE-PTCDI NW-based phototransistor.

Single-crystalline n-channel organic nanowires and their photoinduced charge-carrier dynamics

유호정,오준학 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Single-crystalline nano/microwires (NWs/MWs) based on organic semiconductors have attracted great interest recently as they are promising building blocks for optoelectronic applications. The development of organic phototransistors (OPTs) based on n-channel NWs/MWs is highly desirable for the bottom-up fabrication of photoelectronic circuits, which provides high operational stability, easy control of photoswitching voltages, high photosensitivity and responsivity. To date, however, single-crystalline NWs/MWs OPTs have been far less employed. Herein, we report organic single-crystalline NW-OPTs fabricated using a high-performance n-channel organic semiconductor, N,N'-bis(2-phenethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI), mainly focusing on the photoelectronic characteristics. Highly sensitive and reproducible photo-responses compared with vacuum-deposited thin-film devices were observed from the NWs/MWs OPTs and photogenerated charge carrier behaviors were quantitatively investigated.

Flexible Organic Phototransistor Array with Enhanced Responsivity via Metal–Ligand Charge Transfer

Liu, Xien,Lee, Eun Kwang,Kim, Dong Yeong,Yu, Hojeong,Oh, Joon Hak American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.11

<P>Phototransistors based on organic photoactive materials combine tunable light absorption in the spectral region from Ultraviolet to near-infrared with low-temperature process ability over large areas on flexible substrates. However, they often exhibit low photoresponsivity because of low molar extinction coefficient of photoactive components. We report a simple, yet highly efficient solution method for enhancing the performance of organic phototransistors using ruthenium complex 1 (Ru-complex 1). An air-stable n-type organic semiconductor, N,Ni-bis(2-phenyl ethyl)-perylane-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI), has been deposited on a silicon wafer and a transparent polyimide (PI) substrate vacuum. The BPE-PTCDI phototransistors functionalized with Ru-complex 1 exhibit similar to 5000 times higher external quantum efficiency (EQE) than that of pristine BPE-PTCDI phototransistors, owing to the metal ligand charge transfer (MLCT) from Ru-complex 1, to the active component of the device. In addition, a large 10 X 10 phototransistor array (2.5 X 2.5 cm(2)) has been prepared on a transparent PI substrate, showing distinct light mapping. The fabricated phototransistor array is highly flexible and twistable and works well under tensile and compressive strains. We believe that our simple method will pave a viable way for improvements in the photoresponsivity of organic semiconductors for applications in wearable organic optoelectronic devices.</P>

Flexible organic phototransistors based on a combination of printing methods

Kim, M.,Ha, H.J.,Yun, H.J.,You, I.K.,Baeg, K.J.,Kim, Y.H.,Ju, B.K. Elsevier Science 2014 Organic electronics Vol.15 No.11

Highly photosensitive organic phototransistors (OPTs) are successfully demonstrated on a flexible substrate using all-solution process as well as a combination of printing methods which consist of roll-to-plate reverse offset printing (ROP), inkjet printing and bar coating. Excellent electrical switching characteristics are obtained from heterogeneous interfacial properties of the reverse-offset-printed silver nanoparticle electrode and the inkjet-printed p-channel polymeric semiconductor. In particular, the OPTs exhibit remarkably photosensitivity with a photo-to-dark current ratio exceeding 5 orders. This optoelectronic properties of the combinational printed OPTs are theoretically and experimentally studied, and found the comparable tendency. In addition, excellent mechanical stability is observed with up to 0.5% of strain applied to the OPTs. Hence, by manufactured with a combination of various graphic art printing methods such as roll-to-plate ROP, inkjet printing, and bar coating, these devices are very promising candidates for large-area and low-cost printed and flexible optoelectronics applications.

High‐Performance Phototransistors Based on Single‐Crystalline n‐Channel Organic Nanowires and Photogenerated Charge‐Carrier Behaviors

Yu, Hojeong,Bao, Zhenan,Oh, Joon Hak WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.5

<P><B>Abstract</B></P><P>The photoelectronic characteristics of single‐crystalline nanowire organic phototransistors (NW‐OPTs) are studied using a high‐performance n‐channel organic semiconductor, <I>N</I>,<I>N′</I>‐bis(2‐phenylethyl)‐perylene‐3,4:9,10‐tetracarboxylic diimide (BPE‐PTCDI), as the photoactive layer. The optoelectronic performances of the NW‐OPTs are analyzed by way of their current–voltage (<I>I</I>–<I>V</I>) characteristics on irradiation at different wavelengths, and comparison with corresponding thin‐film organic phototransistors (OPTs). Significant enhancement in the charge‐carrier mobility of NW‐OPTs is observed upon light irradiation as compared with when performed in the dark. A mobility enhancement is observed when the incident optical power density increases and the wavelength of the light source matches the light‐absorption range of the photoactive material. The photoswitching ratio is strongly dependent upon the incident optical power density, whereas the photoresponsivity is more dependent on matching the light‐source wavelength with the maximum absorption range of the photoactive material. BPE‐PTCDI NW‐OPTs exhibit much higher external quantum efficiency (EQE) values (≈7900 times larger) than thin‐film OPTs, with a maximum EQE of 263 000%. This is attributed to the intrinsically defect‐free single‐crystalline nature of the BPE‐PTCDI NWs. In addition, an approach is devised to analyze the charge‐transport behaviors using charge accumulation/release rates from deep traps under on/off switching of external light sources.</P>

Organic Nanowire-Gold Nanorod Hybrid Nanomaterials-based Near-Infrared Phototransistors

정지형,윤민지,임주원,이윤호,김동하,오준학 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Near-infrared (NIR) phototransistors have recently emerged as an important technical platform because of their high potential for a wide range of advanced applications. Herein, we report the opto-electrical performances of NIR phototransistors based on gold nanorods (Au NRs)-decorated n-type organic semiconductor, N,N`-bis(2-phenylethyl)-perylene- 3,4:9,10-tetracarboxylic diimide (BPE-PTCDI) nanowire. By way of the synergetic effect from excellent photo-electrical characteristics of singlecrystalline organic semiconductor BPE-PTCDI NW and localized surface plasmon resonances (LSPR) of Au NRs, the hybrid nanomaterialbased phototransistors accomplish highly enhanced photo-responsivity (R), photo-current/dark-current ratio (P), and external quantum efficiency (EQE) under monochromatic light irradiation compared with those of pristine BPE-PTCDI NW-based ones. Importantly, the photodetectivity of Au NRs in the NIR spectral region has become feasible using their LSPR effect.