10.1021/acsami.6b15631.s001 Chunyu Liu Chunyu Liu Dezhong Zhang Dezhong Zhang Zhiqi Li Zhiqi Li Xinyuan Zhang Xinyuan Zhang Wenbin Guo Wenbin Guo Liu Zhang Liu Zhang Liang Shen Liang Shen Shengping Ruan Shengping Ruan Yongbing Long Yongbing Long Boosted Electron Transport and Enlarged Built-In Potential by Eliminating the Interface Barrier in Organic Solar Cells American Chemical Society 2017 WF champion power conversion efficiency electron injection devices TiO 2 ETL TiO 2 film PCE Boosted Electron Transport PL barrier PC 71 BM electron transfer acceptor charge carrier recombination TiO 2 electron transport layer TRTPL V oc PFN interlayer TiO 2 J sc photoluminescence Organic Solar Cells interface modification strategy 2017-02-24 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Boosted_Electron_Transport_and_Enlarged_Built-In_Potential_by_Eliminating_the_Interface_Barrier_in_Organic_Solar_Cells/4718920 A smart interface modification strategy was employed to simultaneously improve short-circuit current density (<i>J</i><sub>sc</sub>) and open-circuit voltage (<i>V</i><sub>oc</sub>) by incorporating a poly­[(9,9-bis­(3′-(<i>N</i>,<i>N</i>-dimethylamion)­propyl)-2,7-fluorene)-<i>alt</i>-2,7-(9,9-dioctyl)-fluorene] (PFN) interlayer between a TiO<sub>2</sub> film and an active layer, arising from the fact that PFN effectively eliminated the interface barrier between TiO<sub>2</sub> and the fullerene acceptor. The work function (WF) of TiO<sub>2</sub> was apparently reduced, which facilitated effective electron transfer from the active layer to the TiO<sub>2</sub> electron 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 (PC<sub>71</sub>BM) acceptor to TiO<sub>2</sub> ETL, contributing to enhanced <i>J</i><sub>sc</sub>. The shift in vacuum level altered the WF of PC<sub>71</sub>BM, which enlarged the internal electrical field at the donor/acceptor interface and built-in potential (<i>V</i><sub>bi</sub>) across the device. Dark current characteristics and Mott–Schottky measurements indicated the enhancement of <i>V</i><sub>bi</sub>, benefiting to increased <i>V</i><sub>oc</sub>. 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.