Practical Factors Lowering Conversion Efficiency of Hot Carrier Solar Cells

Takeda, Yasuhiko; Tagaya, Motohiro; König, Dirk; Aliberti, P.; Feng, Yuqing; Shrestha, Santosh; Conibeer, Gavin

doi:10.1143/apex.3.104301

Cited by 46 publications

(60 citation statements)

References 13 publications

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“…9,20 Additional to the relaxation time, two more time scales have a major effect on the performance of HCSCs. 21 Firstly, the carrier equilibration (or thermalisation) time t eq is a measure for the rate with which an equilibrium carrier distribution (at elevated temperature) is established. Since the ESCs extract carriers only within a narrow energy range at E e and E h , these levels could quickly deplete and limit the extractable current.…”

Section: Solar Cell Design Principles and Practical Limitsmentioning

confidence: 99%

“…A short t eq serves to repopulate this level and should be at least 1000 times faster than carrier relaxation. 21 Secondly, the carrier extraction time t ex (also called retention time) describes the duration of carrier presence in the absorber. On first glance, a short time seems desired to minimise relaxation losses, but rapid extraction will also reduce the carrier concentration within the absorber.…”

Section: Solar Cell Design Principles and Practical Limitsmentioning

confidence: 99%

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Hot carrier solar cells and the potential of perovskites for breaking the Shockley–Queisser limit

2019

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Section: Solar Cell Design Principles and Practical Limitsmentioning

confidence: 99%

Section: Solar Cell Design Principles and Practical Limitsmentioning

confidence: 99%

Hot carrier solar cells and the potential of perovskites for breaking the Shockley–Queisser limit

2019

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“…The reduction of η max in fast extraction regime III in Fig. 10 may be confusing because the hot carrier solar cells that are targeted in this regime can surpass the SQ limit of η SQ theoretically [3][4][5][6][7] . Therefore, we may expect an increase in η max as τ out decreases in regime III.…”

Section: A a Limiting Case: Heat-shared Phonon Reservoirsmentioning

confidence: 99%

Nonequilibrium Theory of the Conversion Efficiency Limit of Solar Cells Including Thermalization and Extraction of Carriers

et al. 2018

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The ideal solar cell conversion efficiency limit known as the Shockley-Queisser (SQ) limit, which is based on a detailed balance between absorption and radiation, has long been a target for solar cell researchers. While the theory for this limit uses several assumptions, the requirements in real devices have not been discussed fully. Given the current situation in which research-level cell efficiencies are approaching the SQ limit, a quantitative argument with regard to these requirements is worthwhile in terms of understanding of the remaining loss mechanisms in current devices and the device characteristics of solar cells that are operating outside the detailed balance conditions. Here we examine two basic assumptions: (1) that the photo-generated carriers lose their kinetic energy via phonon emission in a moment (fast thermalization), and (2) that the photo-generated carriers are extracted into carrier reservoirs in a moment (fast extraction). Using a model that accounts for the carrier relaxation and extraction dynamics, we reformulate the nonequilibrium theory for solar cells in a manner that covers both the equilibrium and nonequilibrium regimes. Using a simple planar solar cell as an example, we address the parameter regime in terms of the carrier extraction time and then consider where the conventional SQ theory applies and what could happen outside the applicable range.

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“…For quantitative evaluation of the three points unique to hot-carrier extraction: the equilibration time τ eq and thermalization time τ th in the absorber, and the energyselection widths of the ESCs w esc , we formulate a rate equation to describe the energy distribution of electrons in the CB per unit area n e (ε) [43]. Holes in the VB are assumed to be separated from the electron subsystem so that holes scarcely interact with electrons (see Sect.…”

Section: A Rate Equation Modelmentioning

confidence: 99%

Requisites for Highly Efficient Hot-Carrier Solar Cells

Takeda

2013

Lecture Notes in Nanoscale Science and Technology

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We have constructed new models based on detailed balance of particle and energy fluxes to clarify the operating principle of hot-carrier solar cells (HC-SCs) and find the requisites for high conversion efficiency. Energy dissipation due to thermalization of photogenerated carriers can be significantly reduced, even though the thermalization time is not sufficiently long. Instead, the energy dissipation related to entropy generation associated with hot-carrier extraction is remarkable. The thermalization time must be several nanoseconds to exceed the Shockley-Queisser limit under the 1 sun solar irradiation and over 10 ns to compete against triple-junction solar cells at 1,000 sun. The other requisites unique to hot-carrier extraction are a short carrier equilibration time being around one-thousandth of the thermalization time, and an energy-selection width of energy-selective contacts (ESCs) for mono-energetic carrier extraction, which is needed to match the quasi-Fermi levels in the hot absorber and in the cold electrodes, being narrower than 0.1 eV. It seems extremely challenging to fulfill all the requisites, although investigations for material development as well as new concepts for post conventional HC-SCs are underway. IntroductionIn a conventional solar cell, a photon whose energy is higher than the bandgap of the light-absorbing material used in the cell is absorbed to generate a carrier with an energy equal to the photon energy. However, carrier energies in excess of the bandgap of the absorber immediately dissipate by emitting phonons whose temperature equals the room temperature, namely, thermalization of carriers occurs within several picoseconds in most cases. Therefore, the excess carrier energies cannot be

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Practical Factors Lowering Conversion Efficiency of Hot Carrier Solar Cells

Cited by 46 publications

References 13 publications

Hot carrier solar cells and the potential of perovskites for breaking the Shockley–Queisser limit

Hot carrier solar cells and the potential of perovskites for breaking the Shockley–Queisser limit

Nonequilibrium Theory of the Conversion Efficiency Limit of Solar Cells Including Thermalization and Extraction of Carriers

Requisites for Highly Efficient Hot-Carrier Solar Cells

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