The influence of molecular orientation on organic bulk heterojunction solar cells

Tumbleston, John R.; Collins, Brian A.; Yang, Liqiang; Stuart, Andrew C.; Gann, Eliot; Ma, Wei; You, Wei; Ade, Harald

doi:10.1038/nphoton.2014.55

Cited by 448 publications

(493 citation statements)

References 34 publications

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“…There has been considerable recent interest in controlling molecular orientation in organic semiconducting glasses (1)(2)(3)(4)(5)(6)(7). Whereas one might expect all glasses to be isotropic because of their structural disorder, Yokoyama et al and other groups have shown that molecular orientation in vapor-deposited glasses can be quite anisotropic (3,4,8,9) and depend upon deposition conditions (3).…”

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confidence: 99%

“…It has also been shown that oriented layers can improve device lifetime (15) and charge mobility (16)(17)(18). Given the potential utility of controlling molecular orientation in device layers (4,5,7), it is desirable to understand the extent to which molecular orientation can be tuned in glasses made from a particular compound and the mechanistic origins of this effect. Anisotropic glassy solids are also of interest for applications in optics and optoelectronics (19).…”

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confidence: 99%

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Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

Dalal

Walters

Lyubimov

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

193

348

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Physical vapor deposition is commonly used to prepare organic glasses that serve as the active layers in light-emitting diodes, photovoltaics, and other devices. Recent work has shown that orienting the molecules in such organic semiconductors can significantly enhance device performance. We apply a high-throughput characterization scheme to investigate the effect of the substrate temperature (T substrate ) on glasses of three organic molecules used as semiconductors. The optical and material properties are evaluated with spectroscopic ellipsometry. We find that molecular orientation in these glasses is continuously tunable and controlled by T substrate /T g , where T g is the glass transition temperature. All three molecules can produce highly anisotropic glasses; the dependence of molecular orientation upon substrate temperature is remarkably similar and nearly independent of molecular length. All three compounds form "stable glasses" with high density and thermal stability, and have properties similar to stable glasses prepared from model glass formers. Simulations reproduce the experimental trends and explain molecular orientation in the deposited glasses in terms of the surface properties of the equilibrium liquid. By showing that organic semiconductors form stable glasses, these results provide an avenue for systematic performance optimization of active layers in organic electronics.glasses | organic semiconductors | molecular orientation | physical vapor deposition | high-throughput characterization

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confidence: 99%

mentioning

confidence: 99%

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

Dalal

Walters

Lyubimov

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

193

348

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show abstract

“…An open question is therefore whether precise morphological tuning can indeed harvest what energetically resembles a passed-up opportunity. Even in bulk heterojunctions, the device characteristics continue to be pinned by these lowest-energy configurations -despite the "traditional" picture of bulk heterojunctions suggesting the coexistence of a variety of donor-acceptor interfaces with different orientations, in-plane extensions, degrees of intermixing, and hence different energetics [202]. Nevertheless, the open-circuit voltage of bulk heterojunctions is usually on the order of 0.1 eV smaller than in the planar setup, and still correlated with a single CT energy extracted from absorption and electroluminescence.…”

Section: Vice and Virtue Of Low-energy Configurationsmentioning

confidence: 99%

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

Poelking

2018

Springer Theses

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The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors The rational design of organic semiconductors for optoelectronic devices relies on a detailed understanding of how their molecular and morphological structure condition the energetics and dynamics of charged and excitonic states. Investigating the role of molecular architecture, conformation, orientation and packing, this work reveals mechanisms that shape the spatially resolved densities of states in organic, small-molecular and polymeric heterostructures and mesophases. The underlying computational framework combines multiscale simulations of the material morphology at atomistic and coarse-grained resolution with a long-range-polarized embedding technique to resolve the electronic structure of the molecular solid. We show that longrange electrostatic interactions tie the energetics of microscopic states to the mesoscopic structure, with a qualitative and quantitative impact on charge-carrier level profiles across organic interfaces. The computational approach provides quantitative access to the charge-density-dependent opencircuit voltage of planar heterojunctions. The derived and experimentally verified relationships between molecular orientation, architecture, level profiles and open-circuit voltage rationalize the acceptor-donor-acceptor pattern for donor materials in high-performing solar cells. Proposing a pathway for barrier-less dissociation of charge transfer states, we highlight how mesoscale fields generate charge splitting and detrapping forces in systems with finite interface roughness. The associated design rules reflect the dominant role played by lowest-energy configurations at the interface. Acknowledgements 121 Die (nicht-)lokale Zustandsdichte elektronischer Anregungen in organischen Halbleitern List of Publications 123Bibliography 125 Chapter 1 Organic Electronics in a NutshellThe discovery of conductive polymers in the 1970s [1,2] -rewarded with the Nobel prize in chemistry in the year 2000 -and subsequent development of the first polymeric electronic devices in the 1980s [3-5] have marked the beginnings of a vast interdisciplinary research field referred to as organic electronics. Drawing from both polymeric and small-molecular semiconductors, organic thin-film transistors, solar cells, light-emitting diodes, photodetectors and sensors name just a few out of many applications that make use of the supreme chemical versatility and mechanical flexibility of the underlying "soft" molecular materials. Furthermore enabling low-temperature solution-based processing, printing and spray coating, organic electronics is set to complement the conventional silicon-based electronics in diverse waysadding functionality and improving sustainability. This introductory chapter will provide a short review of the materials and device physics, as well as of new trends and challenges that emerged in the field over the past decade. MaterialsOrganic semiconductors are molecular materials that exist at the interface between orga...

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“…[39,40] The detailed processing conditions such as the amount of additive, the donor to acceptor ratio, and the thickness of the active layer were systematically optimized (Table S1−S4, Supporting Information), and the data of best device performance are summarized in Table 2. Without additive treatment, the PCEs of P1−P4 were 5.50%, 5.60%, 7.35%, and 5.27%, respectively.…”

Section: Wwwadvelectronicmatdementioning

confidence: 99%

Steric‐Hindrance Modulation toward High‐Performance 1,3‐Bis(thieno[3,4‐b]thiophen‐6‐yl)‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione‐Based Polymer Solar Cells with Enhanced Open‐Circuit Voltage

Zhang

Zhou

et al. 2017

Adv Elect Materials

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Solution‐processed bulk‐heterojunction polymer solar cells (PSCs) are indispensable in photovoltaics. π‐Conjugated donor–acceptor copolymers as electron donors have become the cornerstone as the most intensively studied topic in this field. Thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) is one of the most commonly used electron‐withdrawing moieties. Based on TPD, a new building block, 1,3‐bis(thieno[3,4‐b]thiophen‐6‐yl)‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (TBTT), is designed and a novel low‐bandgap TPD‐copolymer is developed with a power conversion efficiency (PCE) up to 7.5% with a low open‐circuit voltage (Voc) of 0.633 V when utilizing PC71BM as electron acceptor. To promote the performance of TBTT‐based polymers, four conjugated copolymers are designed and synthesized based on TBTT and benzodithiophene (BDT) building blocks by regulating their steric hindrance with side alkyl chains on BDT moiety. PSCs based on polymer P4 with an additional n‐hexyl side chain blended with PC71BM deliver a high PCE of 9.1% with a Voc of 0.78 V increased by 24%, which is among the highest in TPD‐based polymers. The study provides new insights into the molecular design and synthesis of high‐performance photovoltaic materials.

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The influence of molecular orientation on organic bulk heterojunction solar cells

Cited by 448 publications

References 34 publications

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

Steric‐Hindrance Modulation toward High‐Performance 1,3‐Bis(thieno[3,4‐b]thiophen‐6‐yl)‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione‐Based Polymer Solar Cells with Enhanced Open‐Circuit Voltage

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