Influence of photon recycling on lifetime and diffusion coefficient in GaAs

Renaud, Philippe; Raymond, Frédéric; Bensaïd, B.; Vèrié, C.

doi:10.1063/1.351179

Cited by 43 publications

(29 citation statements)

References 13 publications

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“…At high carrier densities, the radiative recombination lifetimes, τ , are (0.46 ± 0.03) ns, (1.64 ± 0.01) ns and (2.22 ± 0.14) ns, for GaAs DH layers on GaAs, SU‐8 and air, respectively. These results are consistent with inhibition of spontaneous emission by use of low‐index substrates and, therefore, significant enhancements in the emission lifetime as well as the photon recycling . Figure c plots 1/ τ as a function of

n_{sub}^{2} + 1

, where n sub is the refractive index of the substrate material ( n sub = 3.5, 1.5 and 1.0 for GaAs, SU‐8 and air, respectively).…”

Section: Resultssupporting

confidence: 75%

Device Architectures for Enhanced Photon Recycling in Thin‐Film Multijunction Solar Cells

Sheng

Yun

Zhang

et al. 2014

Advanced Energy Materials

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primarily due to the ineffective use of the entire solar spectrum. [ 1 ] Multijuction (MJ) cells, by contrast, spectrally split sunlight into sub-cells with different bandgaps, thereby providing pathways to greatly improved effi ciencies. [6][7][8][9][10][11][12][13] Conventional MJ cells require lattice matched or metamorphic epitaxial growth of the individual sub-cells. In addition, the serially connected sub-cells are constrained by current matching since the photocurrent of a two-terminal MJ device is determined by the smallest current among the sub-cells. These considerations constrain options in material selection, thereby creating practical challenges to the growth of more than three junctions in high performance cells. Our recent work demonstrates the ability to use printing techniques to assemble microscale, multijunction, multi-terminal cells with refractive-index matched interfaces, to yield ultrahigh cell and module effi ciencies. [ 13 ] In spite of the promise of such approaches, interfaces that are index matched are unable to recycle and extract infrared photons needed to approach the detailed balance effi ciency limit. [ 14 ] Figure 1 a illustrates the challenge in a simple example of a stack of two sub-cells with a refractive-index matched (highindex) interface, to minimize interface refl ection losses. The high bandgap top cell absorbs photons with energies above its bandgap ( hν 1 > hν g , where hν g is the bandgap of the top cell), Multijunction (MJ) solar cells have the potential to operate across the entire solar spectrum, for ultrahigh effi ciencies in light to electricity conversion.Here an MJ cell architecture is presented that offers enhanced capabilities in photon recycling and photon extraction, compared to those of conventional devices. Ideally, each layer of a MJ cell should recycle and re-emit its own luminescence to achieve the maximum possible voltage. This design involves materials with low refractive indices as interfaces between sub-cells in the MJ structure. Experiments demonstrate that thin-fi lm GaAs devices printed on low-index substrates exhibit improved photon recycling, leading to increased open-circuit voltages ( V oc ), consistent with theoretical predictions. Additional systematic studies reveal important considerations in the thermal behavior of these structures under highly concentrated illumination. Particularly when combined with other optical elements such as anti-refl ective coatings, these architectures represent important aspects of design for solar cells that approach thermodynamic effi ciency limits for full spectrum operation.

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n_{sub}^{2} + 1

, where n sub is the refractive index of the substrate material ( n sub = 3.5, 1.5 and 1.0 for GaAs, SU‐8 and air, respectively).…”

Section: Resultssupporting

confidence: 75%

Device Architectures for Enhanced Photon Recycling in Thin‐Film Multijunction Solar Cells

Sheng

Yun

Zhang

et al. 2014

Advanced Energy Materials

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“…We note that although it is well-known that photon recycling does influence the photoluminescence in high quality inorganic semiconductors 61 , 62 , we have not implemented it here due to the small role played by this effect in large single crystals (see above).…”

Section: Resultsmentioning

confidence: 99%

Consolidation of the optoelectronic properties of CH3NH3PbBr3 perovskite single crystals

et al. 2017

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Ultralow trap densities, exceptional optical and electronic properties have been reported for lead halide perovskites single crystals; however, ambiguities in basic properties, such as the band gap, and the electronic defect densities in the bulk and at the surface prevail. Here, we synthesize single crystals of methylammonium lead bromide (CH3NH3PbBr3), characterise the optical absorption and photoluminescence and show that the optical properties of single crystals are almost identical to those of polycrystalline thin films. We observe significantly longer lifetimes and show that carrier diffusion plays a substantial role in the photoluminescence decay. Contrary to many reports, we determine that the trap density in CH3NH3PbBr3 perovskite single crystals is 1015 cm−3 , only one order of magnitude lower than in the thin films. Our enhanced understanding of optical properties and recombination processes elucidates ambiguities in earlier reports, and highlights the discrepancies in the estimation of trap densities from electronic and optical methods.

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“…(Additionally, t is time, G is the generation rate, c is the speed of light, n s is the refractive index, P stay is the optical probability of photon escape, and P l is the probability that light will be emitted with a given wavelength.) The experimentally measured external bimolecular rate had to be adjusted to account for photon recycling (29,30). All absorption of photons is assumed to result in the creation of e --h + pairs, but only the bimolecular channel is radiative (with the spectrum as shown in Fig.…”

Section: Solar Cellsmentioning

confidence: 99%

Photon recycling in lead iodide perovskite solar cells

Pazos-Outón

Szumilo

Lamboll

et al. 2016

Science

625

678

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Lead-halide perovskites have emerged as high-performance photovoltaic materials. We mapped the propagation of photogenerated luminescence and charges from a local photoexcitation spot in thin films of lead tri-iodide perovskites. We observed light emission at distances of ≥50 micrometers and found that the peak of the internal photon spectrum red-shifts from 765 to ≥800 nanometers. We used a lateral-contact solar cell with selective electron- and hole-collecting contacts and observed that charge extraction for photoexcitation >50 micrometers away from the contacts arose from repeated recycling between photons and electron-hole pairs. Thus, energy transport is not limited by diffusive charge transport but can occur over long distances through multiple absorption-diffusion-emission events. This process creates high excitation densities within the perovskite layer and allows high open-circuit voltages.

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Influence of photon recycling on lifetime and diffusion coefficient in GaAs

Cited by 43 publications

References 13 publications

Device Architectures for Enhanced Photon Recycling in Thin‐Film Multijunction Solar Cells

Device Architectures for Enhanced Photon Recycling in Thin‐Film Multijunction Solar Cells

Consolidation of the optoelectronic properties of CH3NH3PbBr3 perovskite single crystals

Photon recycling in lead iodide perovskite solar cells

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