Impurity photovoltaic effect in silicon

Guttler, G.; Queisser, H. J.

doi:10.1016/0013-7480(70)90068-9

Cited by 75 publications

(12 citation statements)

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“…If we assume that the built-in voltage V bi is dropped mostly across the IB region, then t = w 2 µV bi (24) where µ is the electron mobility in the IB region. Thus, for an IB region just thick enough to absorb the subgap light [31],…”

Section: Prospects For Ibpvmentioning

confidence: 99%

Nonradiative lifetimes in intermediate band photovoltaics—Absence of lifetime recovery

Krich

Halperin

Aspuru‐Guzik

2012

Journal of Applied Physics

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Intermediate band photovoltaics hold the promise of being highly efficient and cost effective photovoltaic cells. Intermediate states in the band gap, however, are known to facilitate nonradiative recombination. Much effort has been dedicated to producing metallic intermediate bands in hopes of producing lifetime recovery -an increase in carrier lifetime as doping levels increase. We show that lifetime recovery induced by the insulator-to-metal transition will not occur, because the metallic extended states will be localised by phonons during the recombination process. Only trivial forms of lifetime recovery, e.g., from an overall shift in intermediate levels, are possible. Future work in intermediate band photovoltaics must focus on optimizing subgap optical absorption and minimizing recombination, but not via lifetime recovery.The development of novel highly-efficient photovoltaic (PV) devices has the potential to significantly address the global energy and carbon problems. The vast majority of commercial solar cells are made from singlejunction semiconductors, an architecture which Shockley and Queisser showed has an absolute efficiency limit of 41% (with concentrated sunlight) [1]. Among the proposals to break this limit is the intermediate band (IB) photovoltaic, which has an efficiency limit of 63%, considerably higher than the single-junction limit [2,3].A standard single-junction semiconductor PV must optimise its band gap to maximise the product of current and voltage; these compete because it can absorb only photons with energy greater than the band gap E g , and the supplied voltage can be no larger than E g /e, where −e is the electron charge. An IBPV device, illustrated in Fig. 1, has an extra set of levels inside the semiconductor band gap; two subgap photons can be absorbed by the IB layer, producing a single electron-hole pair. Electrical contact is made only to the standard n-and p-type layers, so the IB layer produces extra current while allowing the full band gap to set the limit on the voltage, giving the considerably elevated efficiency bound of 63% [2]. The IBPV effect has been demonstrated in a number of systems [4][5][6], though it has not yet produced high efficiency cells.One method for making a material with an IB is to dope a semiconductor with large concentrations of dopants that form donor (or acceptor) levels deep inside the band gap. There is an obvious problem with this recipe: levels deep in the band gap are well known to cause nonradiative recombination [7,8]. It was proposed that a sufficiently high concentration of dopants could cause an insulator to metal transition (IMT) in the IB, which would suppress the nonradiative recombination rate and cause lifetime recovery in which adding additional dopants decreases the nonradiative recombination rate [9]. A great deal of work has gone into looking for such an IMT in doped semiconductors [10][11][12][13][14][15], including a report of lifetime recovery [16]. A b s o r b e d i n h o s t A b s o r b e d i n I B IB n p E g CB VB V μ e...

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Section: Prospects For Ibpvmentioning

confidence: 99%

Nonradiative lifetimes in intermediate band photovoltaics—Absence of lifetime recovery

Krich

Halperin

Aspuru‐Guzik

2012

Journal of Applied Physics

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“…Shockley and I already briefly discussed this phenomenon of an "impurity-photovoltaic effect", and we remarked that the additionally induced recombination would most probably outweigh the enhanced absorption; 32 this restriction was later treated in more detail at Frankfurt University by G. Güttler in a realistic model and proven in fact to be justified. 46 Solar cells are by their very nature large-area devices, therefore Moore's famous "law" of the dramatic cost reductions for silicon integrated circuits cannot apply. The currently most fashionable nano-structures have, however, been suggested to eventually be helpful: "quantum -well solar cells could have efficiencies of more than thirty per cent."…”

Section: The Next Generationsmentioning

confidence: 99%

“…This review article in a physics journal, bearing the vociferous title "Bright outlook for solar cells". 46 is highly optimistic in its forecasts, but gravely bemoans the insufficient government support in many countries, including the United States. It quotes our physicist colleague David Carroll from Wake Forest University in North Carolina (USA) that "there are no technical challenges that cannot be overcome" and, with bold courage: "there are no physical laws that prevent really high-efficiency devices from being built".…”

Section: The Next Generationsmentioning

confidence: 99%

Detailed balance: lifetimes and efficiencies

Queisser

2007

SPIE Proceedings

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Lifetimes of minority carriers in semiconductors are very important parameters for devices, especially for solar cells. For germanium and silicon, it was discovered that the actually measured lifetimes were by orders of magnitude smaller than the theoretical limit, which can be deduced from the principle of detailed balance of black-body radiative absorption and emission. The thermodynamic limit of solar cell efficiency was also derived based on this principle. The development of solar cells with silicon and its non-ideal junction behavior are reviewed. The contemporary suggested trends to overcome this detailed balance limit are being discussed.

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“…This allows the absorption of low-energy photons and causes them to contribute to the generated photocurrent via two-photon absorption. However, as shown experimentally by (Guettler & Queisser, 1970), the introduction of intermediate levels via impurities will create non-radiative recombination centers and cause a degradation of the solar cell efficiency. This effect was studied theoretically by (Würfel, 1993) and (Keevers & Green, 1994), with the conclusion that the introduced impurity levels can increase the efficiency in some cases, but only marginally.…”

Section: Introductionmentioning

confidence: 99%