title: Boosted Electron Transport and Enlarged Built-In Potential by Eliminating the Interface Barrier in Organic Solar Cells.
abstract: A smart interface modification strategy was employed to simultaneously improve short-circuit current density (Jsc) and open-circuit voltage (Voc) by incorporating a poly[(9,9-bis(3'-(N,N-dimethylamion)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl)-fluorene] (PFN) interlayer between a TiO2film and an active layer, arising from the fact that PFN effectively eliminated the interface barrier between TiO2and the fullerene acceptor. The work function (WF) of TiO2was apparently reduced, which facilitated effective electron transfer from the active layer to the TiO2electron transport layer (ETL) and suppressed charge carrier recombination between contact interfaces. Electron injection devices with and without a PFN interlayer were fabricated to prove the eliminated electron barrier, meanwhile photoluminescence (PL) and time-resolved transient photoluminescence (TRTPL) were measured to probe much easier electron transfer from [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) acceptor to TiO2ETL, contributing to enhanced Jsc. The shift in vacuum level altered the WF of PC71BM, which enlarged the internal electrical field at the donor/acceptor interface and built-in potential (Vbi) across the device. Dark current characteristics and Mott-Schottky measurements indicated the enhancement of Vbi, benefiting to increased Voc. Consequently, the champion power conversion efficiency for a device with a PFN interlayer of 0.50 mg/mL reached to 7.14%, which is much higher than the PCE of 5.76% for the control device.
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University , 2699 Qianjin Street, Changchun 130012, People's Republic of China.
authors.forename: Chunyu
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University , 2699 Qianjin Street, Changchun 130012, People's Republic of China.
authors.forename: Dezhong
authors.initials: D
authors.lastname: Zhang
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University , 2699 Qianjin Street, Changchun 130012, People's Republic of China.
authors.forename: Zhiqi
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University , 2699 Qianjin Street, Changchun 130012, People's Republic of China.
authors.forename: Xinyuan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University , 2699 Qianjin Street, Changchun 130012, People's Republic of China.
authors.forename: Wenbin
authors.identifier: http://orcid.org/0000-0002-7105-0908
authors.initials: W
authors.lastname: Guo
authors.affiliation: College of Instrumentation & Electrical Engineering, Jilin University , 938 Ximinzhu Street, Changchun 130061, People's Republic of China.
authors.forename: Liu
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University , 2699 Qianjin Street, Changchun 130012, People's Republic of China.
authors.forename: Liang
authors.initials: L
authors.lastname: Shen
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University , 2699 Qianjin Street, Changchun 130012, People's Republic of China.
authors.forename: Shengping
authors.initials: S
authors.lastname: Ruan
authors.affiliation: School of Electronic Engineering, South China Agricultural University , Guangzhou, 510642, China.
authors.forename: Yongbing
authors.initials: Y
authors.lastname: Long
keywords: built-in potential; electron transport; interface barrier; interface modification; work function