Dependence of Exciton Diffusion Length and Diffusion Coefficient on Photophysical Parameters in Bulk Heterojunction Organic Solar Cells

Yeboah, Douglas; Singh, Jai

doi:10.1007/s11664-017-5679-2

Cited by 24 publications

(11 citation statements)

References 97 publications

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“…As shown in figure 4., on increasing Nt from 10 10 to 10 11 cm −3 , the output parameters fall off drastically in agreement with the equation (1).The PCE shows a drop from 9.17% and 1.19% significantly, we have set the calibrated value of Nt at 10 12 cm −3 ,since the diffusion length corresponding to 10 11 cm −3 cannot be realised in experiment [51].…”

Section: Effect Of Defect Density Of the Active Layersupporting

confidence: 65%

“…The effect of defect density on the output performance of solar cell is studied using the SRH recombination model [50] with the equation being: where n, p refers to the mobile electron-hole concentration, and n t ,p t being the trap defect concentration with n i ,the intrinsic concentration. The lifetime τ is given by the relation [51]:…”

Section: Effect Of Defect Density Of the Active Layermentioning

confidence: 99%

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Numerical modelling of non-fullerene organic solar cell with high dielectric constant ITIC-OE acceptor

Nithya

Sudheer

2020

J. Phys. Commun.

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The low dielectric constant of organic semiconductors has been a limiting factor in the organic photovoltaics. Non-Fullerene Acceptor Bulk Heterojunction (NFA-BHJ) organic solar cells with high dielectric constant acceptors have been gaining a lot of attention. No simulation work has been done on NFA-BHJ organic solar cell with a high dielectric constant acceptor so far to study the influence of various material parameters on the device performance. In this work, a comprehensive device modelling of the conventional structure of NFA-BHJ with poly [(2,6-(4,8-(PBDB-T)as the polymer donor and (3,9-bis(2-methylene-(3-(1,1 -dicyanomethylene)-indanone)-5,5,11,11-tetraki(4-hexylphenyl)-dithieno [2,3-d:2,3d]-s-indaceno [1,2-b:5,6-b]dithiophene)) with Oligo-Ethylene side chain (ITIC-OE) as the nonfullerene acceptor is performed. We did a detailed analysis on the impact of technological parameters on the cell performance and optimized the device characteristics to produce improved efficiency. Numerical simulation is done using SCAPS 1-D program and the validity of simulated output has been verified by comparing with the measurements from reported literature. Optimization of the device parameters produced an improved device performance with an open circuit voltage of 0.9562 V , short circuit current density of mA cm −2 , Fill factor of 69.75% and a power conversion efficiency of 11% . The results are encouraging to develop NFA-BHJ organic solar cells with high dielectric constant acceptors in the near future.

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Section: Effect Of Defect Density Of the Active Layersupporting

confidence: 65%

Section: Effect Of Defect Density Of the Active Layermentioning

confidence: 99%

Numerical modelling of non-fullerene organic solar cell with high dielectric constant ITIC-OE acceptor

Nithya

Sudheer

2020

J. Phys. Commun.

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“…In another study, Baulin et al [43] compared the dynamics of CT states generated through electron-transfer and hole-transfer exciton-dissociation pathways in three BHJ OSCs, and they found that the dynamics of CT state recombination are very similar for the two charge-generation processes, implying that the nature of the generated CT states is independent of the pathways of CT formation. They did, however, observe that the generation of CT states and free charge carriers greatly depends on the actual LUMO energy offset ∆E LUMO = E D LUMO − E A LUMO (electron transfer) and the HOMO energy offset ∆E HOMO = E D HOMO − E A HOMO (hole transfer) of the blended system [44]. These energy offsets are independent of the pathway of the formation of CT excitons.…”

Section: Introductionmentioning

confidence: 96%

“…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%

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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“…For efficient exciton separation and charge extraction in bulk-heterojunction organic solar cells, the thickness of the photoactive donor–acceptor blend layer is limited by the exciton diffusion length, which is typically significantly less than 50 nm. , Thus, light absorption as well as charge generation and transport have to be optimized to achieve the best performance. Therefore, it is of great importance to find ways to tailor the photoactive layer morphology in order to enhance light absorption, to increase the delocalization of excitonic states by J-aggregation, and to improve vertical charge mobility.…”

Section: Introductionmentioning

confidence: 99%

Structural Templating of an Organic Solar Cell Absorber by Ellagic Acid To Tune Its Aggregation, Molecular Orientation, and Optical Properties

Bittrich

Domke

Levichkova

et al. 2021

ACS Appl. Energy Mater.

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Structural templating with homogeneous template layers is one of the strategies for controlling the orientation of small molecular absorbers in the photoactive layer of an organic solar cell to increase its power conversion efficiency. A main challenge thereby is the energetic alignment of the template molecules to the photoactive and charge-transporting materials. In the present study, the effects of a cluster-like template layer of ellagic acid (EA) on the morphology and optical properties of side-chain-substituted dicyanovinyl quaterthiophene (DCV4T-Et 2 ) thin films are discussed. In the monolayer regime, J-aggregation of DCV4T-Et 2 is confirmed. Insertion of the EA template layer leads to an improved aggregation behavior and formation of J-aggregates in DCV4T-Et 2 films near the EA interface. The orientation of DCV4T-Et 2 molecules in 30 nm thick films changes from "edgeon" to "face-on" due to a π−π interaction between the flat-lying EA molecules and the DCV4T-Et 2 molecules. The face-on orientation by templating is preserved in blend layers with C 60 , and a considerable increase in the crystallinity of the DCV4T-Et 2 phase in the blend is induced. Organic solar cells based on templated DCV4T-Et 2 :C 60 active layers exhibit more than a 50% increase in the efficiency compared to nontemplated active layers. The short-circuit current density and the fill factor are significantly improved. Although the energetic alignment of EA is not ideal, no additional open-circuit voltage losses were observed with templating, due to the cluster-like morphology of the EA layer. Our results demonstrate a cluster-like templating approach with the novel template molecule EA to tailor the molecular orientation, crystallinity, and consequently optical properties of organic semiconducting molecules without significant energetic losses favorable for use in organic electronics.

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Dependence of Exciton Diffusion Length and Diffusion Coefficient on Photophysical Parameters in Bulk Heterojunction Organic Solar Cells

Cited by 24 publications

References 97 publications

Numerical modelling of non-fullerene organic solar cell with high dielectric constant ITIC-OE acceptor

Numerical modelling of non-fullerene organic solar cell with high dielectric constant ITIC-OE acceptor

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

Structural Templating of an Organic Solar Cell Absorber by Ellagic Acid To Tune Its Aggregation, Molecular Orientation, and Optical Properties

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