title: High-Efficiency Polymer LEDs with Fast Response Times Fabricated via Selection of Electron-Injecting Conjugated Polyelectrolyte Backbone Structure.
abstract: Imidazolium ionic side-group-containing fluorene-based conjugated polyelectrolytes (CPEs) with different π-conjugated structures, poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (F8im-Br) and poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-(benzo(2,1,3)thiadiazol-4,8-diyl) dibromide (F8imBT-Br), are synthesized and utilized as an electron injection layer (EIL) in green-emitting F8BT polymer light-emitting diodes (PLEDs). Both CPE EIL devices significantly outperform Ca cathode devices; 17.9 cd A(-1) (at 3.8 V) and 16.6 lm W(-1) (at 3.0 V) for F8imBT-Br devices, 11.1 cd A(-1) (at 4.2 V) and 9.1 lm W(-1) (at 3.4 V) for F8im-Br devices, and 7.2 cd A(-1) (at 3.6 V) and 7.0 lm W(-1) (at 3.0 V) for Ca devices. Importantly, unlike the F8im-Br EIL devices, F8imBT-Br PLEDs exhibit much faster electroluminescence turn-on times (<10 μs) despite both EILs possessing the same tethered imidazolium and mobile bromide ions. The F8imBT-Br devices represent, to the best of our knowledge, the highest efficiency in thin (70 nm) single-layer F8BT PLEDs in conventional device architecture with the fastest EL response time using CPE EIL with mobile ions. Our results clearly indicate the importance of an additional factor of EIL materials, specifically the conjugated backbone structure, to determine the device efficiency and response times.
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Minwon
authors.initials: M
authors.lastname: Suh
authors.affiliation: Department of Physics & Centre for Plastic Electronics, Imperial College London , Prince Consort Road, London SW7 2AZ, United Kingdom.
authors.forename: Jim
authors.initials: J
authors.lastname: Bailey
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Sung Wook
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Kyungmok
authors.initials: K
authors.lastname: Kim
authors.affiliation: Samsung Advanced Institute of Technology (SAIT) , Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do 443-803, Republic of Korea.
authors.forename: Dong-Jin
authors.initials: DJ
authors.lastname: Yun
authors.affiliation: Samsung Advanced Institute of Technology (SAIT) , Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do 443-803, Republic of Korea.
authors.forename: Youngsuk
authors.initials: Y
authors.lastname: Jung
authors.affiliation: Department of Physics & Centre for Plastic Electronics, Imperial College London , Prince Consort Road, London SW7 2AZ, United Kingdom.
authors.forename: Iain
authors.initials: I
authors.lastname: Hamilton
authors.affiliation: Department of Physics & Centre for Plastic Electronics, Imperial College London , Prince Consort Road, London SW7 2AZ, United Kingdom.
authors.forename: Nathan
authors.initials: N
authors.lastname: Chander
authors.affiliation: Department of Physics & Centre for Plastic Electronics, Imperial College London , Prince Consort Road, London SW7 2AZ, United Kingdom.
authors.forename: Xuhua
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Physics & Centre for Plastic Electronics, Imperial College London , Prince Consort Road, London SW7 2AZ, United Kingdom.
authors.forename: Donal D C
authors.initials: DD
authors.lastname: Bradley
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Duk Young
authors.initials: DY
authors.lastname: Jeon
authors.affiliation: Department of Physics & Centre for Plastic Electronics, Imperial College London , Prince Consort Road, London SW7 2AZ, United Kingdom.
authors.forename: Ji-Seon
authors.initials: JS
authors.lastname: Kim
keywords: F8BT; benzothiadiazole; conjugated polyelectrolytes; diodes; electron injection layers; polymer light-emitting