Time-Resolved Neutron Reflectometry and Photovoltaic Device Studies on Sequentially Deposited PCDTBT-Fullerene Layers

Clulow, Andrew J.; Tao, Chen; Lee, Kwan H.; Velusamy, Marappan; McEwan, Jake A.; Shaw, Paul E.; Yamada, Norifumi L.; James, M. R.; Burn, Paul L.; Gentle, Ian R.; Meredith, Paul

doi:10.1021/la5020779

Cited by 38 publications

(37 citation statements)

References 37 publications

(94 reference statements)

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“…Among the materials selected for LL solution processing, P3HT/PCBM (or ICBA) system was mostly stu died, [95,[97][98][99][100][101][102][104][105][106][107][108][109][110][111]113,115,119,120,[124][125][126] and a remarkable PCE of 6.48% was achieved for P3HT/IC 70 BA system. [107] Other polymer donors, [103,112,114,116,127] small molecule donors, [118,123] and even non-fullerene acceptors were also used. [96,112,123] For example, the LL solution-processed devices based on polymer donor PBDTTT-C-T and PC 61 BM acceptor exhibited a PCE of 7.13% without additives, much better than the traditional BHJ structure (4.31%).…”

Section: Sequential Spin Castingmentioning

confidence: 99%

“…With LL processing method, vertical phase separation can be taken into control for the benefit of charge transportation and collection at the appropriate electrodes. [108,110,114,118,122,123,127] By spin coating the donor and acceptor materials in a correct order and using thermal annealing method, a p-i-n like structure can be achieved with donors aggregating to the anode and acceptors to the cathode, which is opposite for the traditional BHJ OPVs with conventional structure.…”

Section: Sequential Spin Castingmentioning

confidence: 99%

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Layer‐by‐Layer Processed Organic Solar Cells

Wang

Zhan

2016

Advanced Energy Materials

104

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Layer‐by‐layer (LL) processes, i.e., sequential deposition of different active layers, are widely used in the fabrication of organic solar cells (OSCs). Recently, LL vacuum deposition and LL solution processes have attracted considerable attention. LL processing presents some advantages over the blend method: a) donor and acceptor layers can be easily and independently controlled and optimized; b) the charge carriers dissociated from excitons at the donor–acceptor interface are confined to each phase, so bimolecular recombination losses can be reduced; c) bilayer geometries enable an easier way for understanding the physical processes taking place at the donor–acceptor interface; d) desired vertical phase separation for charge extraction can be obtained through changing the sequence of donor and acceptor deposition. This report summarizes the recent developments of LL processed OSCs. The remaining problems and challenges, and the key research direction in near future are discussed.

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Section: Sequential Spin Castingmentioning

confidence: 99%

Section: Sequential Spin Castingmentioning

confidence: 99%

Layer‐by‐Layer Processed Organic Solar Cells

Wang

Zhan

2016

Advanced Energy Materials

104

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“…However, the formation of BHJ morphology is an extremely complicated process and the formed morphology is also a highly delicate balance involving many parameters such as domain size, purity, miscibility, etc. [23][24][25] The bilayer structure should be more favorable for charge transport as the separated charges can easily transport to each electrode through the D or A layer with low possibility of recombination. What is worse, the morphology control becomes much more challenging when the device area is scaled up, for example, the morphology of printed film may vary drastically when the processing condition changes.…”

mentioning

confidence: 99%

High‐Performance Large‐Area Organic Solar Cells Enabled by Sequential Bilayer Processing via Nonhalogenated Solvents

Dong

Zhang

Xie

et al. 2018

Advanced Energy Materials

168

161

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power conversion efficiency (PCE) of BHJ devices strongly depends on phase separation of the donor and acceptor. However, the formation of BHJ morphology is an extremely complicated process and the formed morphology is also a highly delicate balance involving many parameters such as domain size, purity, miscibility, etc. To achieve high-performance devices, much effort has been devoted to delicately control the morphology of the active layer (such as the blend ratio between the donor and acceptor, [9][10][11] the type of solvent, [12][13][14] the type and amount of processing additive, [15][16][17] and thermal and solvent annealing [18][19][20] ) to obtain optimal interpenetrated nanoscale phase separation. What is worse, the morphology control becomes much more challenging when the device area is scaled up, for example, the morphology of printed film may vary drastically when the processing condition changes. For this reason, there are typically large performance drops when OPV devices are scaled up to large area or processed using printing techniques. [21,22] Moreover, green solvent is a prerequisite for the commercialization of OSCs. However, for the BHJ structure, the solubility and miscibility of both the donor and acceptor must be taken into consideration together, which limits the selection of a processing solvent. Most OSCs were processed with toxic halogen solvents, and only a few high-performances donor/acceptor combinations were reported in the literature using low toxicity/nontoxic solvents.In contrast, sequential deposition of the donor and acceptor materials followed by post thermal annealing can lead to a similar BHJ morphology and reasonably efficient OSC devices. The interpenetration between donor and acceptor during the solution processing ensures the D/A interfaces for separation of the charges. [23][24][25] The bilayer structure should be more favorable for charge transport as the separated charges can easily transport to each electrode through the D or A layer with low possibility of recombination. [26][27][28] In addition, as both donor and acceptor layers can be processed and optimized independently, this bilayer structure should show less dependence on the D/A ratio, solvent, additive, etc., when compared with the BHJ structure. These properties make the bilayer structure very attractive for achieving high-performance OSCs and While the performance of laboratory-scale organic solar cells (OSCs) continues to grow over 13%, the development of high-efficiency large area OSCs still lags. One big challenge is that the formation of bulk heterojunction morphology is an extremely complicated process and the formed morphology is also a highly delicate balance involving many parameters such as domain size, purity, miscibility, etc. The morphology control becomes much more challenging when the device area is scaled up. In this work, a highly efficient (12.9%) nonfullerene organic solar cell processed using a sequential bilayer deposition method from nonhalogenated solvents, is reported. Using this bi...

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“…Neutron scattering has been highly effective in probing the structure of polymer:fullerene BHJs as contrast between these materials originates from differences in the scattering length density (SLD) of fullerenes compared to protonated conjugated polymers, with no additional deuteration of the components being necessary. For this reason, neutron scattering techniques such as Small Angle Neutron Scattering (SANS)313233343536 and Neutron Reflectivity363738394041 have provided new insight into the nanomorphology and vertical layer structure of bulk heterojunctions42.…”

mentioning

confidence: 99%

Understanding and controlling morphology evolution via DIO plasticization in PffBT4T-2OD/PC71BM devices

Zhang

Parnell

Pontecchiani

et al. 2017

Sci Rep

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We demonstrate that the inclusion of a small amount of the co-solvent 1,8-diiodooctane in the preparation of a bulk-heterojunction photovoltaic device increases its power conversion efficiency by 20%, through a mechanism of transient plasticisation. We follow the removal of 1,8-diiodooctane directly after spin-coating using ellipsometry and ion beam analysis, while using small angle neutron scattering to characterise the morphological nanostructure evolution of the film. In PffBT4T-2OD/PC71BM devices, the power conversion efficiency increases from 7.2% to above 8.7% as a result of the coarsening of the phase domains. This coarsening process is assisted by thermal annealing and the slow evaporation of 1,8-diiodooctane, which we suggest, acts as a plasticiser to promote molecular mobility. Our results show that 1,8-diiodooctane can be completely removed from the film by a thermal annealing process at temperatures ≤100 °C and that there is an interplay between the evaporation rate of 1,8-diiodooctane and the rate of domain coarsening in the plasticized film which helps elucidate the mechanism by which additives improve device efficiency.

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Time-Resolved Neutron Reflectometry and Photovoltaic Device Studies on Sequentially Deposited PCDTBT-Fullerene Layers

Cited by 38 publications

References 37 publications

Layer‐by‐Layer Processed Organic Solar Cells

Layer‐by‐Layer Processed Organic Solar Cells

High‐Performance Large‐Area Organic Solar Cells Enabled by Sequential Bilayer Processing via Nonhalogenated Solvents

Understanding and controlling morphology evolution via DIO plasticization in PffBT4T-2OD/PC71BM devices

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