Correlation of π-Conjugated Oligomer Structure with Film Morphology and Organic Solar Cell Performance

Fitzner, Roland; Mena‐Osteritz, Elena; Mishra, Amaresh; Schulz, Gisela L.; Reinold, Egon; Weil, Mat­thias; Körner, Christian; Ziehlke, Hannah; Elschner, Chris; Leo, Karl; Riede, Moritz; Pfeiffer, Martin; Uhrich, Christian; Bäuerle, Peter

doi:10.1021/ja302320c

Cited by 269 publications

(225 citation statements)

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“…As mentioned above, because SubNc and SubPc have similar LUMO energy levels, a decrease in V OC is circumvented, contrary to previously reported cascade structures 21,27 . This results in an improved performance for the three-layer energy cascade structure, with the best performing device generating a PCE of 8.4%, surpassing the current state-of-the-art evaporated single-junction OPV devices 37,38 . For certification purposes, devices with a 1-cm 2 active area were fabricated and measured in-house with an average PCE of 7.81%, and 7.93% for the best performing device.…”

Section: Resultsmentioning

confidence: 98%

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

et al. 2014

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In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Förster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.

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Section: Resultsmentioning

confidence: 98%

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

et al. 2014

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“…4.8d): These include pentacene (PEN), sexithiophene (6T), zinc phthalocyanine (ZnPc), the merocyanine dye EL86 [128], and the acceptor-substituted oligothiophene D5M [9]. Of these materials, only EL86 and D5M have a ground-state dipole moment due to their donor-acceptor (DA) and cis-acceptor-donor-acceptor (ADA) architecture.…”

Section: Interplay Of Molecular Architecture Packing and Orientationmentioning

confidence: 99%

“…With the mean of the DOS extracted from calculations on thin films (Fig. 6.7), the iso-density open-circuit voltage for these From intersecting the two trends, we can determine the temperature-dependent steady-state charge density p * as 9) In this expression, the prefactor α captures field-enhancement or -reduction of charge generation and thus also incorporates morphological features. Eq.…”

Section: Charge Transfer Energetics and Open-circuit Voltagementioning

confidence: 99%

“…Based on the type of their conjugated molecular building blocks, they are broadly categorized into small-molecular [6] vs. polymeric semiconductors [7]. The associated large compound space (Table 1.1 only lists a very small selection) presents a challenge for rational compound design in general and synthetic chemistry in particular, as already small changes in the backbone and side-chain structure, side-chain length [8][9][10], and, for polymers, regioregularity and molecular weight [11,12] may significantly alter the macroscopic material properties.The conjugated architecture, however, is shared by all compounds, and becomes manifest in the π-π interactions that result from the intermolecular van-der-Waals attraction between 1 2 …”

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confidence: 99%

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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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“…Despite numerous investigations of polymeric properties on the performance of organic field effect transistors and solar cell applications, [10][11][12][13] this topic has not been explored with the same intensity in the field of organic light emitting diodes (OLEDs). [14][15][16] Therefore, we have chosen these types of devices due to their potential as light sources and the major influence that the electroluminescent layer has on the properties of the device.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Molecular Weight and Size Dispersion of the Electroluminescent Polymer on the Performance of Air-Stable Hybrid Light-Emitting Diodes

Martínez‐Ferrero

Grigorian

Ryan

et al. 2015

ACS Appl. Mater. Interfaces

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The influence of the chain length and the molecular weight distribution of the electroluminescent polymer on the carrier transport properties and morphology of air stable Hybrid Light Emitting Diodes is reported. It is found that variations between diverse as-received commercial batches play a major role in the performance of the devices, whose maximum luminance can differ up to two orders of magnitude. Through complementary opto-electronic, structural and morphological characterization techniques we provide insights into the relationship between charge dynamics and the structure of polymeric electroluminescent materials. The carrier dynamics are found to be dominated by both the polymeric chain length and the hole transport, which in turn, is dependent on the concentration of trap states.Furthermore, the chain length is seen to affect the morphology of the active layer.

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Correlation of π-Conjugated Oligomer Structure with Film Morphology and Organic Solar Cell Performance

Cited by 269 publications

References 17 publications

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

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

Influence of the Molecular Weight and Size Dispersion of the Electroluminescent Polymer on the Performance of Air-Stable Hybrid Light-Emitting Diodes

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