Antenna effects and improved efficiency in multiple heterojunction photovoltaic cells based on pentacene, zinc phthalocyanine, and C60

Hong, Ziruo; Lessmann, Rudolf; Maennig, B.; Huang, Qinwen; Harada, Kentaro; Riede, Moritz; Leo, Karl

doi:10.1063/1.3187904

Cited by 43 publications

(41 citation statements)

References 20 publications

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“…Singlet fission is particularly attractive because of the high quantum efficiency (B200%, triplet excitons per photon) in a few well-known organic semiconductors, such as pentacene and Tc, and the prospect of designing and synthesizing new singlet fission molecules 3,4 . Although several research groups have demonstrated solar cells and photodetectors using singlet fission materials [5][6][7][8][9][10] , we are far from understanding how to efficiently harvest singlet fission for enhanced solar energy conversion. Design principles for molecules with high singlet fission yields are starting to emerge 3,4 but little is known about how to optimally extract the two electron-hole pairs resulting from singlet fission.…”

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confidence: 99%

“…One strategy of harvesting singlet fission for solar energy conversion is to form an interface between a singlet fission material (for example, Tc or pentacene) and an electron acceptor (for example, fullerene or inorganic semiconductor quantum dots) for multiple CT (refs [5][6][7][8][9][10]. A limitation of this approach is that CT processes from both the singlet and the triplet pair are possible 11 ; the former does not contribute to any increase in power conversion efficiency beyond the ShockleyQueisser limit and is difficult to avoid for most electron acceptors.…”

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confidence: 99%

“…To circumvent the difficulties presented above, one may couple a singlet fission material (A) and a second chromophore (B) absorbing at longer wavelength with a common electron acceptor (C) 5,7 . Triplet excitons generated via singlet fission in A can transfer through B to reach the interface with C for charge collection.…”

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Harvesting singlet fission for solar energy conversion via triplet energy transfer

Tritsch

Chan

et al. 2013

Nat Commun

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The efficiency of a conventional solar cell may be enhanced if one incorporates a molecular material capable of singlet fission, that is, the production of two triplet excitons from the absorption of a single photon. To implement this, we need to successfully harvest the two triplets from the singlet fission material. Here we show in the tetracene (Tc)/copper phthalocyanine (CuPc) model system that triplets produced from singlet fission in the former can transfer to the later on the timescale of 45±5 ps. However, the efficiency of triplet energy transfer is limited by a loss channel due to faster formation (400±100 fs) and recombination (2.6±0.5 ps) of charge transfer excitons at the interface. These findings suggest a design principle for efficient energy harvesting from singlet fission: one must reduce interfacial area between the two organic chromophores to minimize charge transfer/recombination while optimizing light absorption, singlet fission and triplet rather than singlet transfer.

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Harvesting singlet fission for solar energy conversion via triplet energy transfer

Tritsch

Chan

et al. 2013

Nat Commun

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“…Indeed, several groups have reported layered organic PVs composed of two donor layers [13][14][15][16][17][18][19]. Although different mechanisms, such as double exciton dissociation at the heterojunction of a centered ambipolar donor layer with both the acceptor layer and the other donor layer, have been proposed [13,14,18], an interlayer ET sensitization mechanism has been accepted [15,16,19] [20].…”

Section: Introductionmentioning

confidence: 99%

“…Although different mechanisms, such as double exciton dissociation at the heterojunction of a centered ambipolar donor layer with both the acceptor layer and the other donor layer, have been proposed [13,14,18], an interlayer ET sensitization mechanism has been accepted [15,16,19] [20]. However, in the three-layered donor stack, a donor layer placed farthest from the acceptor layer, corresponding to the donor layer on the left in Fig.…”

Section: Introductionmentioning

confidence: 99%

Cascade-type excitation energy relay in organic thin-film solar cells

Ichikawa¹,

Takekawa²,

Jeon³

et al. 2013

Organic Electronics

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We investigated small-molecule-based organic photovoltaic (PV) cells with three different electron-donating material layers, two thiophene/phenylene co-oligomers [-bis(biphenyl-4-yl)terthiophene (BP3T) and -diphenyl sexithiophene (P6T)] and copper phthalocyanine (CuPc), and one electron-accepting material layer (C 60 ). A cascade-type energy relay between the three donor layers occurred, and the incident photon-current conversion efficiency improved in the blue light region, where CuPc has very low optical absorption. An increase in P6T photoluminescence intensity in a 2 two-layer sample (BP3T/P6T) on quartz confirmed interlayer excitation transfer (ET) from BP3T and P6T. The bulk heterojunction architecture in our interlayer-ET-based organic PV cell was effective. Moreover, P6T appeared to have a relatively long exciton diffusion length of several tens of nanometers.

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Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%

Barito

Sykes

Huang

et al. 2014

Advanced Energy Materials

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Cascade heterojunction (CHJ) organic solar cells have recently emerged as an alternative to conventional bulk heterojunctions and series-connected tandems due to their signifi cant promise for high internal quantum effi ciency (IQE) and broad spectral coverage. However, CHJ devices thus far have also exhibited poor fi ll factor (FF), resulting in minimal enhancements (or even decreases) in power conversion effi ciency (PCE) when compared with single heterojunction (SHJ) cells. In this study, the major variables controlling the CHJ maximum power point and FF are determined using a combinatorial approach. By matching the maximum power point voltage (V MPP) of the constituent parallel-connected heterojunctions (subjunctions) and minimizing the injection barriers intrinsic to CHJs, high FF and PCE can be achieved. Optimized CHJ devices are demonstrated with >99% IQE in the interlayer and a 46% increase in PCE compared to a SHJ reference (4.1% versus 2.8%). Devices with a transparent exciton dissociation layer (EDL)/interlayer/acceptor structure are employed, such that each CHJ has absorption effi ciency identical to its interlayer/acceptor SHJ counterpart. Using these results, a clear map of performance as a function of material parameters is developed, providing straightforward, universal design rules to guide future engineering of molecules and layer architectures for CHJ organic photovoltaic devices.

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Antenna effects and improved efficiency in multiple heterojunction photovoltaic cells based on pentacene, zinc phthalocyanine, and C60

Cited by 43 publications

References 20 publications

Harvesting singlet fission for solar energy conversion via triplet energy transfer

Harvesting singlet fission for solar energy conversion via triplet energy transfer

Cascade-type excitation energy relay in organic thin-film solar cells

Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%

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