Kinetic insight into bimolecular upconversion: experiment and simulation

Piper, Roland; Yoshida, Megumi; Farrell, Daniel; Khoury, Tony; Crossley, Maxwell J.; Schmidt, Timothy W.; Haque, Saif A.; Ekins-Daukes, N. J.

doi:10.1039/c3ra46953k

Cited by 15 publications

(16 citation statements)

References 21 publications

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“…This is responsible for intermediate state lifetimes of order 100 ls measured in molecular up-conversion systems. 38,39 Further, the introduction of the fourth, RB also brings with it an advantage in terms of occupancy of the levels. The position of the IB Fermi energy ensures that the IB is relatively empty, thereby ensuring the VB-IB transition is strong, yet the RB is full, hence a strong RB-CB transition strength.…”

Section: Influence Of Electron Lifetimementioning

confidence: 99%

Intermediate band solar cells: Recent progress and future directions

Okada

Ekins-Daukes

Kita

et al. 2015

Applied Physics Reviews

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340

235

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Extensive literature and publications on intermediate band solar cells (IBSCs) are reviewed. A detailed discussion is given on the thermodynamics of solar energy conversion in IBSCs, the device physics, and the carrier dynamics processes with a particular emphasis on the two-step inter-subband absorption/recombination processes that are of paramount importance in a successful implementation high-efficiency IBSC. The experimental solar cell performance is further discussed, which has been recently demonstrated by using highly mismatched alloys and high-density quantum dot arrays and superlattice. IBSCs having widely different structures, materials, and spectral responses are also covered, as is the optimization of device parameters to achieve maximum performance.

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Section: Influence Of Electron Lifetimementioning

confidence: 99%

Intermediate band solar cells: Recent progress and future directions

Okada

Ekins-Daukes

Kita

et al. 2015

Applied Physics Reviews

Self Cite

340

235

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“…To describe the competition between the various molecular processes, and the resulting dynamics of the TTA systems, rate equations have been employed, 27,[38][39][40][41][42] which have the following general form:…”

Section: Rate Equationsmentioning

confidence: 99%

Photochemical upconversion: present status and prospects for its application to solar energy conversion

Schulze

Schmidt

2015

Energy Environ. Sci.

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518

507

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All photovoltaic solar cells transmit photons with energies below the absorption threshold (bandgap) of the absorber material, which are therefore usually lost for the purpose of solar energy conversion. Upconversion (UC) devices can harvest this unused sub-threshold light behind the solar cell, and create one higher energy photon out of (at least) two transmitted photons. This higher energy photon is radiated back towards the solar cell, thus expanding the utilization of the solar spectrum. Key requirements for UC units are a broad absorption and high UC quantum yield under low-intensity incoherent illumination, as relevant to solar energy conversion devices, as well as long term photostability. Upconversion by triplet-triplet annihilation (TTA) in organic chromophores has proven to fulfil the first two basic requirements, and first proof-of-concept applications in photovoltaic conversion as well as photo(electro)chemical energy storage have been demonstrated. Here we review the basic concept of TTA-UC and its application in the field of solar energy harvesting, and assess the challenges and prospects for its large-scale application, including the long term photostablity of TTA upconversion materials.

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“…Being a bimolecular process, it also gives rise to a non-linear response of the TTA-UC photon yield under low excitation intensity as triplet emitter molecules may decay by a non-radiative first-order loss channel prior to a TTA event. 27 , 49 – 51 The dynamics of the system and the crucial role of the TTA rate has been elucidated by analysis of coupled rate equations: 2 , 46 , 49 , 50 , 52 – 54 …”

Section: Principle Of Tta-ucmentioning

confidence: 99%