title: Strong Composition Effects in All-Polymer Phototransistors with Bulk Heterojunction Layers of p-type and n-type Conjugated Polymers.
abstract: We report the composition effect of polymeric sensing channel layers on the performance of all-polymer phototransistors featuring bulk heterojunction (BHJ) structure of electron-donating (p-type) and electron-accepting (n-type) polymers. As an n-type component, poly(3-hexylthiopehe-co-benzothiadiazole) end-capped with 4-hexylthiophene (THBT-4ht) was synthesized via two-step reactions. A well-studied conjugated polymer, poly(3-hexylthiophene) (P3HT), was employed as a p-type polymer. The composition of BHJ (P3HT:THBT-4ht) films was studied in detail by varying the THBT-4ht contents (0, 1, 3, 5, 10, 20, 30, 40, and 100 wt %). The best charge separation in the P3HT:THBT-4ht films was measured at 30 wt % by the photoluminescence (PL) study, while the charge transport characteristics of devices were improved at the low THBT-4ht contents (<10 wt %). The photosensing experiments revealed that the photosensivity of all-polymer phototransistors was higher than that of the phototransistors with the pristine P3HT layers and strongly dependent on the BHJ composition. The highest (corrected) responsivity (RC) was achieved at 20 wt %, which can be attributable to the balance between the best charge separation and transport states, as investigated for crystal nanostructures and surface morphology by employing synchrotron-radiation grazing-incidence wide-angle X-ray scattering, high-resolution/scanning transmission electron microscopy, and atomic force microscopy.
authors.affiliation: Organic Nanoelectronics Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University , Daegu 41566, Republic of Korea.
authors.forename: Hyemi
authors.initials: H
authors.lastname: Han
authors.affiliation: Organic Nanoelectronics Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University , Daegu 41566, Republic of Korea.
authors.forename: Chulyeon
authors.initials: C
authors.lastname: Lee
authors.affiliation: Organic Nanoelectronics Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University , Daegu 41566, Republic of Korea.|Priority Research Center, Research Institute of Advanced Energy Technology, Kyungpook National University , Daegu 41566, Republic of Korea.
authors.forename: Hwajeong
authors.initials: H
authors.lastname: Kim
authors.affiliation: Organic Nanoelectronics Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University , Daegu 41566, Republic of Korea.
authors.forename: Jooyeok
authors.initials: J
authors.lastname: Seo
authors.affiliation: Organic Nanoelectronics Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University , Daegu 41566, Republic of Korea.
authors.forename: Myeonghun
authors.initials: M
authors.lastname: Song
authors.affiliation: Organic Nanoelectronics Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University , Daegu 41566, Republic of Korea.|Department of Physics, Division of Mathematical, Physical and Life Sciences, University of Oxford , Oxford OX1 3PD, United Kingdom.
authors.forename: Sungho
authors.initials: S
authors.lastname: Nam
authors.affiliation: Organic Nanoelectronics Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University , Daegu 41566, Republic of Korea.
authors.forename: Youngkyoo
authors.identifier: http://orcid.org/0000-0002-9391-2636
authors.initials: Y
authors.lastname: Kim
keywords: all-polymer phototransistors; bulk heterojunction; charge separation; charge transport; responsivity