Effects of Contact-Induced Doping on the Behaviors of Organic Photovoltaic Devices

Wang, Jian; Xu, Liang; Lee, Yun Ju; Villa, Manuel De Anda; Malko, Anton V.; Hsu, Julia W. P.

doi:10.1021/acs.nanolett.5b03473

Cited by 29 publications

(39 citation statements)

References 41 publications

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“…In many cases, it may be possible to identify the dominant recombination mechanism, i.e. Shockley-Read-Hall, radiative or Auger, from an analysis of luminescence yield 12 , luminescence transients 13,14 , ideality factor [15][16][17][18][19] , doping level 17,20,21 , and numerical simulations 22,23 . However, distinguishing between recombination at the interface between absorber and electrodes (surface recombination) and recombination in the bulk of the absorber (bulk recombination) can be extremely challenging 24,25 .…”

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confidence: 99%

Discriminating between surface and bulk recombination in organic solar cells by studying the thickness dependence of the open-circuit voltage

Zonno

Krogmeier

Katte

et al. 2016

Applied Physics Letters

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In case of thin-film solar cells it is often rather difficult to determine what the dominant recombination mechanism is. In particular it is difficult to distinguish recombination at the interface between the absorber layer and the electrodes (typically called surface recombination) from recombination in the bulk of the absorber -or in case of organic solar cells at the internal donor-acceptor interfaces. Here, we suggest a method to distinguish surface and bulk recombination in thin-film solar cells based on the thickness dependence of the saturation current density, which we derive from the open-circuit voltage and the photocurrent at short circuit or reverse bias. By means of numerical simulations, we show that surface and bulk recombination currents scale differently with thickness assuming the material properties to be unchanged. We test our predictions on a range of organic solar cell data from our laboratory and from literature and show that in the field of organic photovoltaics the whole range of cases, from mostly surface limited to purely bulk limited, is observed.

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confidence: 99%

Discriminating between surface and bulk recombination in organic solar cells by studying the thickness dependence of the open-circuit voltage

Zonno

Krogmeier

Katte

et al. 2016

Applied Physics Letters

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“…Charges and their electric fields have a strong impact on the final device characteristics, e.g. exciton diffusion, 7 PL quantum yield [8][9][10] and PL emission wavelength. 4,11 The random formation of charges on a single conjugated polymer chain is responsible for the highly dynamic changes in PL intensity, i.e.…”

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confidence: 99%

Impact of charge carrier injection on single-chain photophysics of conjugated polymers

Hofmann

Vogelsang

Lupton

2016

Applied Physics Letters

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Charges in conjugated polymer materials have a strong impact on the photophysics and their interaction with the primary excited state species has to be taken into account in understanding device properties. Here, we employ single-molecule spectroscopy to unravel the influence of charges on several photoluminescence (PL) observables. The charges are injected either stochastically by a photochemical process, or deterministically in a hole-injection sandwich device configuration. We find that upon charge injection, besides a blue-shift of the PL emission and a shortening of the PL lifetime due to quenching and blocking of the lowest-energy chromophores, the non-classical photon arrival time distribution of the multichromophoric chain is modified towards a more classical distribution. Surprisingly, the fidelity of photon antibunching deteriorates upon charging, whereas one would actually expect the number of chromophores to be reduced. A qualitative model is presented to explain the observed PL changes. The results are of interest to developing a microscopic understanding of the intrinsic charge-exciton quenching interaction in devices.

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“…By applying J = N A eμ h (V/d), the lower limit of μ h for device A is obtained to be 1.4 × 10 −4 cm 2 V −1 s −1 , which is within the range of μ h values (1 × 10 −4 to 6 × 10 −4 cm 2 V −1 s −1 ) reported for P3HT:PCBM BHJ devices. 2,3,40 Devices B and C show typical space-charge limited current behaviors, and we fit their J−V curves between 2 and 10 V using the space-charge limited current−voltage (SCLC) model: 41…”

Section: Resultsmentioning

confidence: 99%

Structural Order: The Dominant Factor for Nongeminate Recombination in Organic Photovoltaic Devices

Wang

Hsu

2017

J. Phys. Chem. C

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Reducing nongeminate recombination (NGR) will provide a major boost to the performance of bulk heterojunction (BHJ) organic photovoltaic (OPV) devices. It is therefore critical to identify the dominant factor(s) that determines NGR. While substantial research effects have been made and various factors have been considered, the determining factor has not been ascertained. After comprehensively evaluating the impact of deep defect states, donor−acceptor interfacial area, and mobility, here we demonstrate that the structural order is the dominant factor that determines NGR in OPV devices. Intensity modulated photovoltage spectroscopy in conjunction with the charge extraction technique is applied to quantitatively measure bimolecular recombination coefficients. A model P3HT:PCBM system with varying composition and annealing temperature, which removes uncontrolled variables yet resembles the behaviors of different polymer donor OPV systems, enables us to reach the unambiguous conclusion. Our findings shed light on key strategies to reduce NGR and pave the road for future high performance OPV design and optimization.

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Effects of Contact-Induced Doping on the Behaviors of Organic Photovoltaic Devices

Cited by 29 publications

References 41 publications

Discriminating between surface and bulk recombination in organic solar cells by studying the thickness dependence of the open-circuit voltage

Discriminating between surface and bulk recombination in organic solar cells by studying the thickness dependence of the open-circuit voltage

Impact of charge carrier injection on single-chain photophysics of conjugated polymers

Structural Order: The Dominant Factor for Nongeminate Recombination in Organic Photovoltaic Devices

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