title: Broadband All-Polymer Phototransistors with Nanostructured Bulk Heterojunction Layers of NIR-Sensing n-Type and Visible Light-Sensing p-Type Polymers.
abstract: We report 'broadband light-sensing' all-polymer phototransistors with the nanostructured bulk heterojunction (BHJ) layers of visible (VIS) light-sensing electron-donating (p-type) polymer and near infrared (NIR) light-sensing electron-accepting (n-type) polymer. Poly[{2,5-bis-(2-ethylhexyl)-3,6-bis-(thien-2-yl)-pyrrolo[3,4-c]pyrrole-1,4-diyl}-co-{2,2'-(2,1,3-benzothiadiazole)]-5,5'-diyl}] (PEHTPPD-BT), which is synthesized via Suzuki coupling and employed as the n-type polymer, shows strong optical absorption in the NIR region (up to 1100 nm) in the presence of weak absorption in the VIS range (400~600 nm). To strengthen the VIS absorption, poly(3-hexylthiophene) (P3HT) is introduced as the p-type polymer. All-polymer phototransistors with the BHJ (P3HT:PEHTPPD-BT) layers, featuring a peculiar nano-domain morphology, exhibit typical p-type transistor characteristics and efficiently detect broadband (VIS~NIR) lights. The maximum corrected responsivity (without contribution of dark current) reaches up to 85~88% (VIS) and 26~40% (NIR) of theoretical responsivity. The charge separation process between P3HT and PEHTPPD-BT components in the highest occupied molecular orbital is proposed as a major working mechanism for the effective NIR sensing.
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Hyemi
authors.initials: H
authors.lastname: Han
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea.|Center for Plastic Electronics and Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Sungho
authors.initials: S
authors.lastname: Nam
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Jooyeok
authors.initials: J
authors.lastname: Seo
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Chulyeon
authors.initials: C
authors.lastname: Lee
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea.|Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Hwajeong
authors.initials: H
authors.lastname: Kim
authors.affiliation: Center for Plastic Electronics and Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.|Department of Engineering Science, Division of Mathematical, Physical and Life Sciences, University of Oxford, 9 Parks Road, Oxford OX1 3PD, United Kingdom.|Department of Physics, Division of Mathematical, Physical and Life Sciences, University of Oxford, 9 Parks Road, Oxford OX1 3PD, United Kingdom.
authors.forename: Donal D C
authors.initials: DD
authors.lastname: Bradley
authors.affiliation: Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, Republic of Korea.
authors.forename: Chang-Sik
authors.initials: CS
authors.lastname: Ha
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Youngkyoo
authors.initials: Y
authors.lastname: Kim