Comparative contributions of singlet and triplet excitons in the performance of organic devices

Singh, Jai; Narayan, Monishka Rita; Ompong, David

doi:10.1002/pssc.201510127

Cited by 3 publications

(5 citation statements)

References 16 publications

(28 reference statements)

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“…Therefore, this FRET process is likely to initiate the two-step exciton dissociation process, which first includes large-scale FRET exciton diffusion from D to DA, and then dissociation at the DA/A interface. However, the FRET process, to be efficient, needs overlapping between the D emission spectrum and the DA absorption spectrum [35][36][37]. In the present case, the absorption spectrum of AlPcCl exhibits two main features, one band between 550 nm and 800 nm and the other one in the UV range from 400 nm and less (Figure 4).…”

Section: Resultsmentioning

confidence: 68%

“…Indeed, we had already shown that AlPcCl can be used as an acceptor layer in binary OPVs [28]. Depending on the organic materials chosen to build the active layer, different models can be used to describe the operating mechanism of ternary OPVs, which are as follows: (i) the classical charge transfer via the four-step process, (ii) the parallel mechanism of which the ternary structure behaves as if it was two diodes in parallel [42], (iii) the formation of an interpenetrating bulk heterojunction structure, which is possible when there is a high degree of compatibility between the donor and the acceptor materials [43], and, finally, (iv) the energy transfer mechanism by Föster resonance energy transfer (FRET) [35][36][37].…”

Section: Discussionmentioning

confidence: 99%

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Ternary Planar Heterojunction Organic Solar Cells Based on the Ternary Active Layers: α-6T/AlPcCl/C60

Ftouhi

Lamkaouane

Diani

et al. 2022

Solar

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Ternary planar heterojunction organic solar cells (PHJ-OPVs) were fabricated using three organic small molecules, alpha-sexithiophene (α-6T), aluminum phthalocyanine chloride (AlPcCl) and fullerene (C60). These molecules can be easily sublimated under a vacuum; they have complementary optical absorption spectra and their energy band structure alignment is favorable for electronic charge transfers. Moreover, α-6T and AlPcCl have almost the same HOMO, which is desirable to avoid any decrease in open circuit voltage. The AlPcCl intercalated layer bridges the energy levels of the electron donor, α-6T, and the electron acceptor, C60, which facilitates charge transport through the energy cascade effect. Moreover, the charge carrier mobility measurements of AlPcCl, using the space charge limited current method, demonstrated that it iss ambipolar. All these properties combine to improve the power conversion efficiency (PCE) of PHJ-OPVs by moving from binary structures (α-6T/C60, α-6T/AlPcCl and AlPcCl/C60) to ternary ones (α-6T/AlPcCl/C60). We show, in this study, that both interfaces of the ternary PHJ-OPVs are efficient for carrier separation. After optimization of the different layer thickness, we show that, by comparing the optimum efficiencies of the binary PHJ-OPVs, the realization of ternary PHJ-OPVs, based on the active layers α-6T/AlPcCl/C60, using the following optimized method, allows us to achieve a PCE of 4.33%.

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Section: Resultsmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 99%

Ternary Planar Heterojunction Organic Solar Cells Based on the Ternary Active Layers: α-6T/AlPcCl/C60

Ftouhi

Lamkaouane

Diani

et al. 2022

Solar

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“…This is physically reasonable, since triplet polaron pairs can be expected to be more strongly bound than singlets. This is certainly true of triplet versus singlet excitons 35 and a more strongly bound pair is expected to have a smaller probability of dissociation. The microscopic parameters obtained by fitting the sample results in Fig.…”

Section: Discussionmentioning

confidence: 99%

Modelling and fitting the Polaron Pair Magnetoconductance model to obtain a realistic local hyperfine field in Tris-(8-hydroxyquinoline)aluminium based diodes

Weng

Gillin

Kreouzis

2019

Sci Rep

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The Polaron Pair (PP) model has been successfully applied to magnetoconductance (MC) in organic semiconductor devices under ultra-small magnetic fields (USMFE). We report µT resolution MC measurements carried out with high sensitivity (better than 10 −6 ) on the common organic semiconductor tris -(8-hydroxyquinoline)aluminium in the range ±500 µT displaying clear minima at ~±240 µT. Unlike traditional approaches, where device MC is simply evaluated using the PP model using nominal parameters for microscopic quantities such as the local hyperfine magnetic field, we have carried out actual fitting of the PP MC model to the experimentally obtained data. The fitting procedure yields physically realistic values for the polaron pair decay rate, local hyperfine magnetic field and triplet contribution to dissociation namely: = 28.6 ± 9.7 MHz, = 0.34 ± 0.04 mT and = 0.99 ± 0.01 respectively. The local hyperfine field obtained by fitting is in excellent agreement with independently calculated values for this system and is reproducible across different devices and independent of drive conditions. This demonstrates the applicability of the fitting approach to any organic USMFE MC data for obtaining microscopic parameter values.

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“…This may be due to the fact that as the two materials, donor and acceptor, are blended together in a BHJ structure, they cannot be separately excited experimentally. However, in order to understand the contributions This has prompted several researchers to investigate the above two processes in more detail [37][38][39][40][41][42][43][44][45][46]. Recently, two different external quantum efficiencies (EQE) due to different donor and acceptor absorption bands have been reported [37].…”

Section: Introductionmentioning

confidence: 99%

“…These energy offsets are independent of the pathway of the formation of CT excitons. Singh et al [45,46] recently studied the contribution of exciton generation in the donor and acceptor materials and its dissociation to the performance of BHJ OSCs. They found that the absorption and dissociation rates as well as exciton diffusion lengths are comparable whether excitons are generated in the donor or acceptor.…”

Section: Introductionmentioning

confidence: 99%

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Yeboah

Singh

2017

Electronics

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Abstract:One of the key parameters in determining the power conversion efficiency (PCE) of bulk heterojunction (BHJ) organic solar cells (OSCs) is the open circuit voltage (V OC ). The processes of exciting the donor and acceptor materials individually in a BHJ OSC are investigated and are found to produce two different expressions for V OC s. Using the contributions of electron and hole quasi-Fermi levels and charge carrier concentrations, the two different V OC expressions are derived as functions of the energetics of the donor and acceptor materials and the photo-generated charge carrier concentrations, and calculated for a set of donor-acceptor blends. The simultaneous excitation of both the donor and acceptor materials is also considered and the corresponding V OC , which is different from the above two, is derived. The V OC calculated from the photoexcitation of the donor is found to be somewhat comparable with that obtained from the photoexcitation of the acceptor in most combinations of the donor and acceptor materials considered here. It is also found that the V OC calculated from the simultaneous excitations of donor and acceptor in BHJ OSCs is also comparable with the other two V OC s. All three V OC s thus derived produce similar results and agree reasonably well with the measured values. All three V OC s depend linearly on the concentration of the photoexcited charge carriers and hence incident light intensity, which agrees with experimental results. The outcomes of this study are expected to help in finding materials that may produce higher V OC and hence enhanced PCE in BHJ OSCs.

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Comparative contributions of singlet and triplet excitons in the performance of organic devices

Cited by 3 publications

References 16 publications

Ternary Planar Heterojunction Organic Solar Cells Based on the Ternary Active Layers: α-6T/AlPcCl/C60

Ternary Planar Heterojunction Organic Solar Cells Based on the Ternary Active Layers: α-6T/AlPcCl/C60

Modelling and fitting the Polaron Pair Magnetoconductance model to obtain a realistic local hyperfine field in Tris-(8-hydroxyquinoline)aluminium based diodes

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

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