Highly Efficient Polymer-Based Optoelectronic Devices Using PEDOT:PSS and a GO Composite Layer as a Hole Transport Layer

Abstract

We demonstrate highly efficient polymer light-emitting diodes (PLEDs), as well as polymer solar cells (PSCs), using a solution-processable poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS):graphene oxide (GO) (PEDOT:GO) composite layer as hole transport layers (HTLs). The PEDOT:GO composite HTL layer shows enhanced charge carrier transport due to improved conductivity by benzoid-quinoid transitions with a well-matched work function between GO (4.89 eV) and PEDOT:PSS (4.95 eV). Moreover, it reduces remarkably exciton quenching and suppresses recombinations that bring higher charge extraction in PSCs and increases the recombinations of holes and electrons within the active layer by the blocking behavior of the electrons from a fluorescent semiconductor due to the existence of GO with large bandgap (∼3.6 eV) in the PEDOT:GO composite layer, therefore leading to an enhancement of device efficiency in PLEDs and PSCs. The optimized PLEDs and PSCs with a PEDOT:GO composite HTL layer shows the maximum luminous efficiency of 21.74 cd/A (at 6.4 V) for PLEDs, as well as the power conversion efficiency of 8.21% for PSCs, which were improved by ∼220 and 12%, respectively, compared to reference PLEDs and PSCs with a PEDOT:PSS layer.

Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide /PEDOT:PSS double decked hole transport layer

“…The ambipolar mobility increased from 3.78 × 10 −4  cm 2 V −1 s −1 in case of PEDOT:PSS HTL to 4.04 × 10 −4  cm 2 V −1 s −1 for single GO HTL and finally to 7.47 × 10 −4  cm 2 V −1 s −1 for the device with GO/PEDOT:PSS double decked HTL, which is almost double of the either of the individual GO or PEDOT:PSS HTLs, and in good agreement with the PCEs of corresponding devices. A quantitative comparison of ambipolar mobility of the OSCs with GO, PEDOT:PSS and GO/PEDOT:PSS HTLs confirmed that use of GO/PEDOT:PSS layer promoted the charge carriers transportation and extraction, particularly the hole mobility, resulting in optimized photovoltaic performance22. Since the only difference in the device architecture is the utilization of different HTLs therefore the increase in the accumulative charge carrier mobility is predominately due to the increased hole mobility using a GO/PEDOT:PSS double decked layer that can lead to balanced charge carrier transportation with an electron-blocking ability and a reduction of the suppression between the HTL and the active layer22.…”

“…in their recent work on planar heterojunction perovskite solar cells, used GO/PEDOT:PSS HTL structure to obtain a stable device with power conversion efficiency (PCE) of 9.74%. Similarly, Yu, Jae Choul et al 22. demonstrated highly efficient polymer light emitting diodes (PLEDs) and OPVs with GO and PEDOT:PSS composite layer as an HTL.…”

“…GO, in aqueous dispersion, exhibits a unique heterogeneous electronic structure due to the presence of mixed sp 2 and sp 3 hybridizations21. However, it lacks good Ohmic contact due to its insulating properties22 Moreover, it is difficult to obtain the full coverage coating of GO at a time. Therefore, recently combination of GO and PEDOT:PSS have been reported to effectively work as an HTL in OPVs.…”

Improved efficiency of indium-tin-oxide-free organic light-emitting devices using PEDOT:PSS/graphene oxide composite anode

“…The functional groups, in this case the epoxy and hydroxyl groups, disrupt the sp 2 conjugation of the hexagonal graphene lattice in the basal plane. Thus, GO behaves as an insulator with a large band gap of around 3.6 eV [20,21,26,27]. This implies that the ratio of GO in PEDOT:PSS-GO composite anode should not be heavy, for avoiding excessive GO leading to low conductivity of the anode.…”

Graphene-based materials for polymer solar cells

“…Theoretical PCEs as high as 12 % have been predicted for graphene-based organic devices [24], and it has also been proposed that graphene may favor charge carrier multiplication [24]. As for practical device applications, graphene has proved to be useful in various parts of PSCs with extraordinary performance, not only as a substitute for indium tin oxide (ITO) electrodes, but also as cathode, electron acceptor, hole extraction and electron extraction material [25][26][27][28][29][30]. In this review, we summarize the research progress about graphene-based PSCs, in which graphene-based materials were used in different layers of PSCs including electrodes, interfacial layers and active layers.…”