Broad spectral sensitivity and improved efficiency in CuPc/Sub-Pc organic photovoltaic devices

Kumar, Hemant; Kumar, Pankaj; Bhardwaj, Ramil; Sharma, G. D.; Chand, Suresh; Jain, S.C.; Kumar, Vikram

doi:10.1088/0022-3727/42/1/015103

Cited by 51 publications

(41 citation statements)

References 26 publications

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“…Specifically, the interfacial layer should possess a lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels between the corresponding LUMO and HOMO energy levels of the donor and acceptor materials. [12][13][14][15][16][17][18] By definition, the cascade requires that the energy of the CT state at the interfacial layer is larger than or equal to the donor-acceptor CT energy. Thus, the introduction of the additional layer is typically associated with an increase in the V OC , at least compared to the bilayer device with a smaller CT state energy.…”

Section: Introductionmentioning

confidence: 99%

“…18 While the increase in V OC appears to be largely a trivial consequence of the higher CT state energy, changes in photocurrent are more significant. Some previous studies have exhibited increased photocurrent due to broader absorption, 17 but we instead focus on the dissociation efficiency of excitons at the cascaded interface.…”

Section: Introductionmentioning

confidence: 99%

“…In an extension of the prior CELA devices, [12][13][14][15][16][17] the cascaded interfaces employed here are designed to destabilize both excitons and bound charge transfer states; see Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

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Reducing recombination losses in planar organic photovoltaic cells using multiple step charge separation

Heidel

Hochbaum

Sussman

et al. 2011

Journal of Applied Physics

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We enhance the efficiency of heterojunction organic solar cells by introducing a thin interfacial layer between the acceptor and donor layers. The interfacial layer energy levels are chosen to provide a gradient for charges crossing the interface, approximating a conventional p-n junction with three organic semiconductors. Devices with interfacial layers exhibit increased open circuit voltage (VOC) and increased short circuit current (JSC). The increase in VOC is due to a reduction in dark current and charge recombination. The increase in JSC is correlated with an increase in the conversion efficiency of excitons originating in the donor or acceptor layers. The interfacial layer destabilizes charge transfer states at the donor-acceptor interface, yielding reduced exciton recombination. The introduction of thin interfacial layers may prove to be an important probe of the physics of exciton separation in organic photovoltaic cells.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reducing recombination losses in planar organic photovoltaic cells using multiple step charge separation

Heidel

Hochbaum

Sussman

et al. 2011

Journal of Applied Physics

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“…The experimental details are given elsewhere. 10 The devices were illuminated with a white light halogen lamp at 200 mW/ cm 2 . Neutral density filters with different optical densities ͑ODs͒ were used to vary the incident illumination intensity.…”

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confidence: 99%

Effect of illumination intensity and temperature on open circuit voltage in organic solar cells

Kumar

Jain

Kumar

et al. 2009

Applied Physics Letters

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The effect of illumination intensity and temperature on open circuit voltage ͑V oc ͒ in organic photovoltaic devices has been investigated. V oc is observed to saturate at high illumination intensities. The illuminated J-V characteristics at different intensities intersect the dark characteristic at a single point. This intersection point is shown to be equal to the built-in voltage ͑V bi ͒ in the sample. A reduction in temperature shows increment in saturated V oc . This increment in saturated V oc is attributed to the variation of V bi with temperature. A model has been presented that explains the observed behavior of V bi at different temperatures. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3129194͔Organic photovoltaic ͑OPV͒ devices can play an important role in generating long-term clean and cheap energy. Power conversion efficiencies and lifetime of these devices are not yet high enough for their commercial viability. Efforts are being made all over the world to understand the physics behind the operation and to improve the performance of these devices. The interpenetrating bulk-heterojunction tandem devices have shown a power conversion efficiency ͑͒ of ϳ6.5%.2 In order to optimize the power conversion efficiency and their reliability in various operating conditions, the complete understanding of device physics is of prime importance. There are various fundamental aspects regarding the physics of OPV devices that require attention. For example, contrary to the Si photovoltaic devices the forward bias current in OPV devices under illumination intersects the dark current and becomes more than the dark current. And another important issue is the origin of V oc . For the design of future solar cells, it is important to understand whether the V oc is a bulk property or an electrode property or a combination of both. It has been suggested that V oc in OPV devices depends either on the difference of energies of highest occupied molecular orbital of the donor and lowest occupied molecular orbital of the acceptor 3,4 or on the difference of the work functions of anode and cathode ͑⌬W͒ used. 5The variation of V oc with temperature 6 and illumination intensity 7,8 cannot be explained by either of these models. Various models have been presented to explain the experimental observations in OPV devices 5,7 yet the physics behind the operation is not well understood and requires more work to be done. Schilinsky et al. 7 extended the standard Si one diode model and a good agreement with the experimental data at different illumination intensities was observed. By self-consistent calculations, Schilinsky et al. 7 showed the existence of a constant electric field in the OPV devices. This finding is an important contribution. The correction due to this electric field was applied to the observed short circuit current ͑J sc ͒. However, the effects of the electric field on the dark currents were not investigated. We have recently presented a model considering the effect of constant electric field on both the dark an...

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“…[7] The optical properties of SubPcs are distinctive as they show intense absorption and emission around 550 nm, leading to a particular focus on their application as components in photovoltaic cells. [7,[11][12][13] A small number of subporphyrins are also known, the most notable examples being the synthetic breakthroughs reported by Osuka and Kobayashi leading to the first syntheses of boron tribenzosubporphyrins 5 [14] and 6 [15] ( Figure 2). The most challenging core modification of the oligopyrrole/indole macrocycles is arguably the generation of hybrid structures [16] that lie between the classic porphyrin and phthalocyanine parent structures.…”

mentioning

confidence: 99%

Synthesis of Meso‐Substituted Subphthalocyanine–Subporphyrin Hybrids: Boron Subtribenzodiazaporphyrins

et al. 2015

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The first syntheses of hybrid structures that lie between subphthalocyanines and subporphyrins are reported. The versatile single‐step synthetic method uses a preformed aminoisoindolene to provide the bridging methine unit and its substituent while trialkoxyborates simultaneously act as Lewis acid, template, and provider of the apical substituent. The selection of each component therefore allows for the controlled formation of diverse, differentially functionalized systems. The new hybrids are isolated as robust, pure materials that display intense absorption and emission in the mid‐visible region. The new compounds are further characterized in solution and solid state by variable‐temperature NMR spectroscopy and X‐ray crystallography, respectively.

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Broad spectral sensitivity and improved efficiency in CuPc/Sub-Pc organic photovoltaic devices

Cited by 51 publications

References 26 publications

Reducing recombination losses in planar organic photovoltaic cells using multiple step charge separation

Reducing recombination losses in planar organic photovoltaic cells using multiple step charge separation

Effect of illumination intensity and temperature on open circuit voltage in organic solar cells

Synthesis of Meso‐Substituted Subphthalocyanine–Subporphyrin Hybrids: Boron Subtribenzodiazaporphyrins

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