Recent progress in the morphology of bulk heterojunction photovoltaics

Brady, Michael A.; Su, Gregory M.; Chabinyc, Michael L.

doi:10.1039/c1sm06147j

Cited by 150 publications

(185 citation statements)

References 118 publications

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“…Secondly, the BHJ growth kinetics is controlled by a coupled crystallization-diffusion mechanism, so the key parameters, such as domain size, phase purity and polymer crystallinity, cannot be varied independently [82]. Thirdly, the disorder and anisotropy of the BHJ morphology at both molecular and nanometric length scales make it difficult to characterize through scattering and microscopy [83]. The design of the OPV structure may provide a new opportunity to overcome the bottleneck of BHJ for the significant improvement of PCE.…”

Section: Opv Structure Designmentioning

confidence: 99%

Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

2014

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Organic photovoltaic cells (OPVs) have been a hot topic for research during the last decade due to their promising application in relieving energy pressure and environmental problems caused by the increasing combustion of fossil fuels. Much effort has been made toward understanding the photovoltaic mechanism, including evolving chemical structural motifs and designing device structures, leading to a remarkable enhancement of the power conversion efficiency of OPVs from 3% to over 15%. In this brief review, the advanced progress and the state-of-the-art performance of OPVs in very recent years are summarized. Based on several of the latest developed approaches to accurately detect the separation of electron-hole pairs in the femtosecond regime, the theoretical interpretation to exploit the comprehensive mechanistic picture of energy harvesting and charge carrier generation are discussed, especially for OPVs with bulk and multiple heterojunctions. Subsequently, the novel structural designs of the device architecture of OPVs embracing external geometry modification and intrinsic structure decoration are presented. Additionally, some approaches to further increase the efficiency of OPVs are described, including thermotics and dynamics modification methods. Finally, this review highlights the challenges and prospects with the aim of providing a better understanding towards highly efficient OPVs.

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Section: Opv Structure Designmentioning

confidence: 99%

Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

2014

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“…In addition to the electronic properties of the constituent semiconductors, the structure of the BHJ has been demonstrated to signifi cantly infl uence the efficiency of photocurrent generation. [9][10][11][12] It is presently believed that BHJ fi lms are characterised by a partially phase separated nanoscale morphology, with co-existing regions of pure polymer, pure fullerene and a mixed polymer/ fullerene phase all being present. [13][14][15][16] Effi cient OPVs are in general characterised by structures that exist over a series of length-scales, including organisation at molecular length-scales and the formation of nanoscale percolated networks, with each length-scale having an important infl uence on the processes of photocurrent generation and charge extraction.…”

mentioning

confidence: 99%

Morphology Development in Amorphous Polymer:Fullerene Photovoltaic Blend Films During Solution Casting

Pearson

Wang

Dunbar

et al. 2013

Adv Funct Materials

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659www.MaterialsViews.com wileyonlinelibrary.com . IntroductionThe ability to process photovoltaic devices using solution-based techniques is an attractive proposition [ 1,2 ] owing to the potential for such devices to be manufactured over large areas at low cost. [ 3 ] Organic photovoltaic (OPV) devices are one category of solution processable photovoltaics that have seen a rapid rise in power conversion effi ciency (PCE) [ 4,5 ] and operating lifetime [ 6 ] in recent years, bringing the technology closer to the specifi cations deemed necessary for commercial viability. [ 7,8 ] The photoactive semiconducting layer within these devices is typically composed of a blend of a conjugated polymer and a functionalised fullerene, forming a self-assembled bulk-heterojunction (BHJ) architecture. In addition to the electronic properties of the constituent semiconductors, the structure of the BHJ has been demonstrated to signifi cantly infl uence the efficiency of photocurrent generation. [9][10][11][12] It is presently believed that BHJ fi lms are characterised by a partially phase separated nanoscale morphology, with co-existing regions of pure polymer, pure fullerene and a mixed polymer/ fullerene phase all being present. [13][14][15][16] Effi cient OPVs are in general characterised by structures that exist over a series of length-scales, including organisation at molecular length-scales and the formation of nanoscale percolated networks, with each length-scale having an important infl uence on the processes of photocurrent generation and charge extraction. To optimise BHJ morphology and create an OPV device having a high PCE requires control over many different parameters, including the choice of solvent, the conditions of fi lm casting and the possible application of post-fi lm deposition techniques.Several studies [17][18][19][20][21][22][23][24][25] have applied a range of techniques to probe the formation and evolution of morphology in polymer:fullerene blend fi lms during various stages in their preparation, drying and post processing in order to gain insight into the dynamic mechanisms that drive morphology evolution. [ 26 ] In addition to an improved physical understanding of such processes, the information obtained is likely to be of signifi cant importance if such materials and devices undergo commercialisation and manufacture, as real-time process control will be a critical requirement. To date, the majority of Morphology Development in Amorphous Polymer:Fullerene Photovoltaic Blend Films During Solution CastingAndrew J. Pearson ,* Tao Wang , Alan D. F. Dunbar , Hunan Yi , Darren C. Watters , David M. Coles , Paul A. Staniec , Ahmed Iraqi , Richard A. L. Jones , and David G. Lidzey * The evolution of fi lm structure is reported during solution casting of PCDTBT:PC 70 BM 1:4 wt%, a polymer:fullerene blend system that fi nds application in an organic photovoltaic device. Using the complimentary techniques of grazing-incidence wide-angle X-ray scattering and spectroscopic ellipsometry, a number of distinct proc...

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“…Energy filtered TEM (EFTEM) is an increasingly common method for enhancing contrast in organic materials. This is accomplished by introducing a post-specimen energy window that only allows electrons having a specific range of energies form the image [4][5][6][7][8][9][10][11]. The motivation behind the use of this technique is that the different materials within the bulk heterojunction (BHJ) have plasmon losses at different energies.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Phase Fraction Detection in Organic Photovoltaic Materials through EELS Imaging

Dyck

Das

et al. 2015

Polymers

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Organic photovoltaic materials have recently seen intense interest from the research community. Improvements in device performance are occurring at an impressive rate; however, visualization of the active layer phase separation still remains a challenge. This paper outlines the application of two electron energy-loss spectroscopic (EELS) imaging techniques that can complement and enhance current phase detection techniques. Specifically, the bulk plasmon peak position, often used to produce contrast between phases in energy filtered transmission electron microscopy (EFTEM), is quantitatively mapped across a sample cross section. A complementary spectrum image capturing the carbon and sulfur core loss edges is compared with the plasmon peak map and found to agree quite well, indicating that carbon and sulfur density differences between the two phases also allows phase discrimination. Additionally, an analytical technique for determining absolute atomic areal density is used to produce an absolute carbon and sulfur areal density map. We show how these maps may be re-interpreted as a phase ratio map, giving quantitative information about the purity of the phases within the junction.

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Recent progress in the morphology of bulk heterojunction photovoltaics

Cited by 150 publications

References 118 publications

Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

Morphology Development in Amorphous Polymer:Fullerene Photovoltaic Blend Films During Solution Casting

Quantitative Phase Fraction Detection in Organic Photovoltaic Materials through EELS Imaging

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