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Boosted Electron Transport and Enlarged Built-In Potential by Eliminating the Interface Barrier in Organic Solar Cells
journal contribution
posted on 2017-02-24, 00:00 authored by Chunyu Liu, Dezhong Zhang, Zhiqi Li, Xinyuan Zhang, Wenbin Guo, Liu Zhang, Liang Shen, Shengping Ruan, Yongbing LongA 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 TiO2 film and an active layer, arising from the fact
that PFN effectively eliminated the interface barrier between TiO2 and the fullerene acceptor. The work function (WF) of TiO2 was apparently reduced, which facilitated effective electron
transfer from the active layer to the TiO2 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 (PC71BM) acceptor
to TiO2 ETL, 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.
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WFchampion power conversion efficiencyelectron injection devicesTiO 2 ETLTiO 2 filmPCEBoosted Electron TransportPLbarrierPC 71 BMelectron transferacceptorcharge carrier recombinationTiO 2 electron transport layerTRTPLV ocPFN interlayerTiO 2J scphotoluminescenceOrganic Solar Cellsinterface modification strategy
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