Organic phototransistors based on solution grown, ordered single crystalline arrays of a π-conjugated molecule

Mukherjee, Biswanath,Sim, Kyoseung,Shin, Tae Joo,Lee, Junghyun,Mukherjee, Moumita,Ree, Moonhor,Pyo, Seungmoon The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.7

<P>High quality, single crystalline, ordered arrays of a π-conjugated organic molecule, <I>N,N′</I>-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C<SUB>8</SUB>), were grown by solution processing and used to fabricate a low-cost, high-performance organic phototransistor (OPT). The single crystalline nature of the microstructure was investigated using 2D-GIXD measurement. The organic field-effect transistor fabricated using periodic arrays of elongated crystals exhibited a photoresponsivity (<I>P</I>) of <I>ca.</I> 1 A W<SUP>−1</SUP> and a photo to dark current ratio (<I>I</I><SUB>on</SUB>/<I>I</I><SUB>off</SUB>) of 2.5 × 10<SUP>3</SUP> at <I>V</I><SUB>G</SUB> = 12 V and a maximum <I>P</I> of <I>ca.</I> 7 A W<SUP>−1</SUP> at the high gate bias regime (<I>V</I><SUB>G</SUB> = 50 V) with an optical power of <I>ca.</I> 7.5 mW cm<SUP>−2</SUP>. With polymeric gate dielectric, the OPT exhibited very stable n-type characteristics both in the dark and under light illumination and showed reproducible photo-switching behavior. The dependence of the photocurrent on the gate/drain voltage and on illumination intensity provided an effective way to control the number of photo-carriers generated in the active material, enabling the precise tuning of the device's performance. Performance comparison between OPTs with ordered crystal arrays and thin films of PTCDI-C<SUB>8</SUB> confirmed that the material's intrinsic properties were better realized in the crystalline device, presumably because of higher charge carrier mobility and better charge transport capability. This one-step, solution-based, self-assembly fabrication of multifunctional (photodetection, photoswitching, signal amplification) optoelectronic devices has potential to aid the development of organic semiconductors with high-quality micro/nanostructures for large-scale application and low-cost optoelectronic devices.</P> <P>Graphic Abstract</P><P>An organic phototransistor (OPT) was fabricated using solution grown, periodic arrays of PTCDI-C<SUB>8</SUB> single crystals. The OPT exhibited high photosensitivity (7 A W<SUP>−1</SUP>), high on/off current ratio (2.5 × 10<SUP>3</SUP>) and reproducible photo-switching at low optical power. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm14179e'> </P>

Control over Multifunctionality in Optoelectronic Device Based on Organic Phototransistor

Mukherjee, Biswanath,Mukherjee, Moumita,Choi, Youngill,Pyo, Seungmoon American Chemical Society 2010 ACS APPLIED MATERIALS & INTERFACES Vol.2 No.6

<P>Highly stable, reproducible, photosensitive organic field-effect transistors based on an <I>n</I>-type organic material, copper hexadecafluorophthalocyanine, and two different polymeric gate dielectrics has been reported and their performances have been compared by evaluating the surface/interface properties. The devices produced a maximum photocurrent gain (<I>I</I><SUB>light</SUB><I>/I</I><SUB>dark</SUB>) of 79 at <I>V</I><SUB>G</SUB> = 7 V and showed the potentiality as multifunctional optoelectronic switching applications depending upon the external pulses. The switching time of the transistor upon irradiation of light pulse, i.e., the photoswitching time of the device, was measured to be ∼10 ms. On the basis of optical or combination of optical and electrical pulses, the electronic/optoelectronic properties of the device can be tuned efficiently. The multifunctions achieved by the single device can ensure very promising material for high density RAM and other optoelectronic applications. Furthermore, as the device geometry in the present work is not limited to rigid substrate only, it will lead to the development of flexible organic optoelectronic switch compatible with plastic substrates.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2010/aamick.2010.2.issue-6/am100127q/production/images/medium/am-2010-00127q_0001.gif'></P>

Periodic arrays of organic crystals on polymer gate dielectric for low-voltage field-effect transistors and complementary inverter

Mukherjee, Biswanath,Shin, Tae Joo,Sim, Kyoseung,Mukherjee, Moumita,Lee, Junghyun,Kim, Sung Hoon,Pyo, Seungmoon Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.41

<P>Periodic arrays of highly oriented 7,7,8,8-tetracyanoquinodimethane (TCNQ) crystals, directly grown on a polymeric gate dielectric through a solution process, are used for the fabrication of a low-voltage organic field-effect transistor (OFET). Consequently, an organic complementary inverter using the TCNQ periodic array (<I>n</I>-channel) and pentacene (<I>p</I>-channel) is also reported. The TCNQ-based <I>n</I>-channel OFET exhibited very stable field-effect characteristics with low operational (2 V) and threshold voltages (<0.5 V). The highest field-effect carrier mobility in the saturation region was found to be 0.03 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>. Furthermore, the organic complementary inverter showed good response characteristics in the low-voltage regime. The swing range of <I>V</I><SUB>OUT</SUB> is same as <I>V</I><SUB>DD</SUB>, ensuring “zero” static power consumption in the digital logic circuit. For the inverter with <I>V</I><SUB>DD</SUB> = 2 V, the noise margin for low and high voltages are 1.0 V and 0.3 V, respectively. The logic threshold (<I>V</I><SUB>IN</SUB> = <I>V</I><SUB>OUT</SUB>) is 1.3 V and the maximum gain (−d<I>V</I><SUB>OUT</SUB>/d<I>V</I><SUB>IN</SUB>) of 4 is obtained at <I>V</I><SUB>IN</SUB> = 1.3 V.</P> <P>Graphic Abstract</P><P>A novel method to produce an ordered organic crystalline array and its use in fabricating high-performance low voltage OFET has been demonstrated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm01220c'> </P>

Solution processed, aligned arrays of TCNQ micro crystals for low-voltage organic phototransistor

Mukherjee, Biswanath,Mukherjee, Moumita,Sim, Kyoseung,Pyo, Seungmoon Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.6

<P>A simple approach is developed to prepare periodic arrays of large, elongated crystals of π-conjugated organic molecules, <I>viz</I>, 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) through a solution based method. The ordered crystalline array is successfully used to fabricate low-voltage organic phototransistors (OPT). The OPT with polymeric gate dielectric exhibits very stable n-type characteristics with a low threshold voltage (<0.5 V). Under illumination, the devices produce a current gain (I<SUB><I>light</I></SUB>/I<SUB><I>dark</I></SUB>) of 31 at <I>V</I><SUB><I>G</I></SUB> = 0.3 V. Photoswitching occurs within 10 ms and photosensitivity is greater than 1 mA W<SUP>−1</SUP> at low driving voltages and low optical powers. The drain current increases gradually with increasing the illumination intensity resulting in typical output FET characteristics. The one-step, solution-based, self-assembly method for highly ordered organic crystals in large area could have significant potential for future large-scale and low-cost optoelectronic devices. In addition, this study aims to aid the development of organic semiconductor materials with high quality crystalline structures for various optoelectronic applications.</P> <P>Graphic Abstract</P><P>A low voltage organic phototransistor (OPT) based on solution processed, highly ordered crystalline arrays of TCNQ exhibits excellent photosensitive field effect characteristics with a photo switching speed <10 ms. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm02513e'> </P>

Optical Control of Electrical Characteristic in Organic complementary Inverter

김성영,Biswanath Mukherjee,임태훈,김효종,심교승,표승문 한국고분자학회 2010 한국고분자학회 학술대회 연구논문 초록집 Vol.2010 No.4

MADF: Mobile-Assisted Data Forwarding for Wireless Data Networks

Xiaoxin Wu,Shueng-Han Gary Chan,Biswanath Mukherjee,Bharat Bhargava,Daniel C. Lee 한국통신학회 2004 Journal of communications and networks Vol.6 No.3

Analysis of Inter-Domain Collaborative Routing: Provider Competition for Clients

Martin O. Nicholes,Chen-Nee Chuah,Shyhtsun Felix Wu,Biswanath Mukherjee 한국통신학회 2011 Journal of communications and networks Vol.13 No.5

Any server offering a routing service in the Internet would naturally be in competition for clients, and clients may need to utilize service from a specific server in order to achieve a desired result. We study the various properties of this competition,such as the fraction of route requests handled by a routing service provider and the fraction of total revenue obtained. As the routing service providers (i.e., servers or routers in this context) compete,they may alter behavior in order to optimize one of the above properties. For example, a service provider may lower the price charged for its service, in order to increase the number of clients served. Our models are based on servers offering a routing service to clients within representative network topologies based on actual Internet sub-graphs. These models provide a framework for evaluating competition in the Internet. We monitor key aspects of the service, as several variables are introduced into the models. The first variable is the fraction of client requests that will pay more for a better quality route. The remaining requests are normal client requests that are satisfied by the most economical route. The second variable is the fraction of servers who choose to lower service prices in order to maximize the number of client requests served. As this fraction increases, it is more likely that a server will lower the price. Finally, there are some resource constraints applied to the model, to increase the dif-ficulty in providing a routing solution, i.e., to simulate a realistic scenario. We seek to understand the effect on the overall network, as service providers compete. In simple cases, we show that this competition could have a negative impact on the overall efficiency of a service. We show that the routing variety present in the larger models is unable to mask this tendency and the routing service performance is decreased due to competition.

Analysis of Inter-Domain Collaborative Routing: Provider Competition for Clients

Nicholes, Martin O,Chuah, Chen-Nee,Wu, Shyhtsun Felix,Mukherjee, Biswanath The Korea Institute of Information and Commucation 2011 Journal of communications and networks Vol.13 No.5

Any server offering a routing service in the Internet would naturally be in competition for clients, and clients may need to utilize service from a specific server in order to achieve a desired result. We study the various properties of this competition, such as the fraction of route requests handled by a routing service provider and the fraction of total revenue obtained. As the routing service providers (i.e., servers or routers in this context) compete, they may alter behavior in order to optimize one of the above properties. For example, a service provider may lower the price charged for its service, in order to increase the number of clients served. Our models are based on servers offering a routing service to clients within representative network topologies based on actual Internet sub-graphs. These models provide, a framework for evaluating competition in the Internet. We monitor key aspects of the service, as several variables are introduced into the models. The first variable is the fraction of client requests that will pay more for a better quality route. The remaining requests are normal client requests that are satisfied by the most economical route. The second variable is the fraction of servers who choose to lower service prices in order to maximize the number of client requests served. As this fraction increases, it is more likely that a server will lower the price. Finally, there are some resource constraints applied to the model, to increase the difficulty in providing a routing solution, i.e., to simulate a realistic scenario. We seek to understand the effect on the overall network, as service providers compete. In simple cases, we show that this competition could have a negative impact on the overall efficiency of a service. We show that the routing variety present in the larger models is unable to mask this tendency and the routing service performance is decreased due to competition.

QoE enhancement schemes for video in converged OFDMA wireless networks and EPONS

Chitimalla, Divya,Tornatore, Massimo,Lee, Sang-Soo,Lee, Han-Hyub,Park, Soomyung,Chung, Hwan Seok,Mukherjee, Biswanath IEEE 2018 Journal of optical communications and networking Vol.10 No.3

<P>Bandwidth requirements of both wireless and wired clients in access networks continue to increase rapidly, primarily due to the growth of video traffic. Application awareness can be utilized in access networks to optimize quality of experience (QoE) of end clients. In this study, we utilize information at the client-side application (e.g., video resolution) to achieve superior resource allocation that improves user QoE. We emphasize optimizing QoE of the system rather than quality of service (QoS), as user satisfaction directly relies on QoE and optimizing QoS does not necessarily optimize QoE, as shown in this study. We propose application-aware resource-allocation schemes on an Ethernet passive optical network (EPON), which supports wireless (utilizing orthogonal frequency division multiple access) and wired clients running video-conference applications. Numerical results show that the application-aware resource-allocation schemes improve QoE for video-conference applications for wired and wireless clients.</P>

Energy-Efficient Virtual Base Station Formation in Optical-Access-Enabled Cloud-RAN

Xinbo Wang,Thota, Saigopal,Tornatore, Massimo,Hwan Seok Chung,Han Hyub Lee,Soomyung Park,Mukherjee, Biswanath IEEE 2016 IEEE journal on selected areas in communications Vol.34 No.5

<P>In recent years, the increasing traffic demand in radio access networks (RANs) has led to considerable growth in the number of base stations (BSs), posing a serious scalability issue, including the energy consumption of BSs. Optical-access-enabled Cloud-RAN (CRAN) has been recently proposed as a next-generation access network. In CRAN, the digital unit (DU) of a conventional cell site is separated from the radio unit (RU) and moved to the 'cloud' (DU cloud) for centralized signal processing and management. Each DU/RU pair exchanges bandwidth-intensive digitized baseband signals through an optical access network (fronthaul). Time-wavelength division multiplexing (TWDM) passive optical network (PON) is a promising fronthaul solution due to its low energy consumption and high capacity. In this paper, we propose and leverage the concept of a virtual base station (VBS), which is dynamically formed for each cell by assigning virtualized network resources, i.e., a virtualized fronthaul link connecting the DU and RU, and virtualized functional entities performing baseband processing in DU cloud. We formulate and solve the VBS formation (VF) optimization problem using an integer linear program (ILP). We propose novel energy-saving schemes exploiting VF for both the network planning stage and traffic engineering stage. Extensive simulations show that CRAN with our proposed VF schemes achieves significant energy savings compared to traditional RAN and CRAN without VF.</P>