Carrier multiplication in bulk and nanocrystalline semiconductors: Mechanism, efficiency, and interest for solar cells

Delerue, Christophe; Allan, G.; Pijpers, Joep J. H.; Bonn, Mischa

doi:10.1103/physrevb.81.125306

Cited by 84 publications

(128 citation statements)

References 33 publications

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“…Atomistic calculations focused on small diameter ( 3 nm) NCs show that CM is dominated by II processes [19,21]. An extrapolation of these calculations to larger NCs and comparison to the bulk have been reported recently [22]. Effective mass models have been used to study direct photogeneration [23] and coherent CM dynamics in larger (4−6 nm) diameter NCs.…”

mentioning

confidence: 99%

“…This allows us to evaluate the contributions of all predicted pathways to the total QE. To clarify the quantum confinement effect on the key quantities determining QE, comparison with the bulk limit is reported on the absolute energy scale [7,22]. In general, performance of the photovoltaic devices can be characterized by variously defined power efficiency [12,22], in particular using the photon energy scale normalized per NC/bulk band gap energy [25].…”

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confidence: 99%

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Numerical Study of Carrier Multiplication Pathways in Photoexcited Nanocrystal and Bulk Forms of PbSe

Velizhanin

Piryatinski

2011

Phys. Rev. Lett.

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Employing the interband exciton scattering model, we have performed a numerical study of the direct photogeneration and population relaxation processes contributing to carrier multiplication (CM) in nanocrystalline and bulk PbSe. We argue that in both cases the impact ionization is the main mechanisms of CM. This explains weak contribution of the direct photogeneration to the total quantum efficiency (QE). Investigated size scaling of QE in NCs and comparison to the bulk limit provide microscopic insight in the experimentally observed trends.

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mentioning

confidence: 99%

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confidence: 99%

Numerical Study of Carrier Multiplication Pathways in Photoexcited Nanocrystal and Bulk Forms of PbSe

Velizhanin

Piryatinski

2011

Phys. Rev. Lett.

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“…One of the interesting properties of semiconductor nanocrystals is the interband Coulomb coupling [5][6][7][8][9][10][11][12][13][14][15][16] that can lead to multiple exciton generation (MEG) 4,17,18 . In the MEG process, absorption of a single photon leads to creation of two or more electron-hole pairs, as schematically depicted in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Because of its importance both for the full understanding of nanocrystal properties as well as for practical applications, the interband Coulomb couplings were extensively studied by various theoretical methods, including density functional theory 5,6 , pseudopotential method [7][8][9][10] , or tight binding approach 11,12,16,24 . Since the ab-initio and atomistic methods are computationally expensive, the less numerically demanding k · p method has also been used in the modeling of Coulomb couplings 13,14,[25][26][27] .…”

Section: Introductionmentioning

confidence: 99%

Interband Coulomb coupling in narrow-gap semiconductor nanocrystals:k·ptheory

Azizi

Machnikowski²

2015

Phys. Rev. B

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We derive the matrix elements of Coulomb interaction between states with different number of electrons and holes in a semiconductor nanocrystal within the 8-band k · p theory. These matrix elements are responsible for multiple exciton generation which may contribute to the enhancement of the efficiency of solar cells. Our calculations are performed within the multi band envelope function formalism based on the states resulting from diagonalization of the 8-band k · p Hamiltonian. We study in detail and compare two contributions to the inter-band Coulomb coupling: the mesoscopic one, which involves only the envelope functions and relies on band mixing, and the microscopic one, that relies on the Bloch parts of the wave functions and is non-zero even between single-band states. We show that these two contributions are of a similar order of magnitude. We study also the statistical distribution of the magnitudes of the inter-band Coulomb matrix elements and show that the overall coupling to remote states decays according to a power law favorable for the convergence of numerical computations.

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“…Other than impact ionization, no effective and practical internal amplification mechanism was found over the past four decades except for scientific demonstrations. 14,15 On the other hand, many fields of industry, including communications, imaging, and sensing, would benefit greatly from another intrinsic amplification process that does not have the limitations of impact ionization.…”

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confidence: 99%

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

Liu

Yan

Zhang

et al. 2015

Applied Physics Letters

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Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanism based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.

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Carrier multiplication in bulk and nanocrystalline semiconductors: Mechanism, efficiency, and interest for solar cells

Cited by 84 publications

References 33 publications

Numerical Study of Carrier Multiplication Pathways in Photoexcited Nanocrystal and Bulk Forms of PbSe

Numerical Study of Carrier Multiplication Pathways in Photoexcited Nanocrystal and Bulk Forms of PbSe

Interband Coulomb coupling in narrow-gap semiconductor nanocrystals:k·ptheory

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

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