Toward Practical Carrier Multiplication: Donor/Acceptor Codoped Si Nanocrystals in SiO<sub>2</sub>

Chung, Nguyen Xuan; Limpens, Rens; Weerd, Chris de; Lesage, Arnon; Fujii, Minoru; Gregorkiewicz, T.

doi:10.1021/acsphotonics.8b00144

Cited by 13 publications

(23 citation statements)

References 47 publications

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“…Note that previous investigations , presented similar PL spectra for the same samples, upon λ exc = 340 nm excitation. Linear absorption spectra have been duplicated from ref and are measured with a dual beam mode PerkinElmer Lambda 950 spectrometer. X-ray diffraction (XRD) patterns are measured on a Rigaku D/MAX2500.…”

Section: Methodssupporting

confidence: 72%

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Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

et al. 2018

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Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron–hole (e–h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P–B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction of the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e–h pairs. This is understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).

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Section: Methodssupporting

confidence: 72%

“…A continuous wave excitation at a wavelength of λ exc = 405 nm is used for both measurements. Note that previous investigations 10,15…”

Section: ■ Methodsmentioning

confidence: 83%

Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

et al. 2018

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“…5 This value is derived upon including the beneficial effect of carrier multiplication (a feature already shown to be facilitated and optimized by close-packed P−B co-doped Si NCs). 14 Our results indicate that this optimal emission energy is already reached in HPB-doped Si NCs with sizes below the critical radius of D critical ≈ 6 nm (Figure 1f). This indicates that their practical feasibility is not limited by the presence of some remaining free carriers in uncompensated NCs.…”

Section: ■ Materials and Methodsmentioning

confidence: 53%

“…5 Recently, a possible game changer arose in the form of codoped Si NCs 11−13 that are simultaneously doped with both phosphorus (P) and boron (B) doping species. With their surface chemistry modifications 13 and optimal carrier multiplication features 14 they might tackle both of these problems at the same time. In parallel to these co-doped structures, singly doped (n-or p-type) Si NCs have shown their value for the optoelectronic industry as well and could be employed as, for example, fluorescent markers for biosensing purposes 15,16 or even photodetectors.…”

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confidence: 99%

Critical Size for Carrier Delocalization in Doped Silicon Nanocrystals: A Study by Ultrafast Spectroscopy

et al. 2018

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We present a comprehensive ultrafast spectroscopy-based study on the delocalization of doping-induced carriers in Si nanocrystals (NCs). To this end we prepare thin films of differently sized doped Si NCs and vary the doping configurations from singly P and B doping to simultaneously P and B co-doping. We show that the NC size orchestrates the level of delocalization of the doping-induced carriers. This can be understood in light of (1) the quantum confinement effect and (2) unscreened Coulomb interactions by moving further into the nanoscale. Both contributions affect the activation energy (ΔE) that is required to create free majority carriers. By varying the NC size in combination with the doping configuration we tune ΔE and control the delocalization of the doping-induced carriers. Most importantly, we show that there is a critical NC diameter of D critical ≈ 6 nm that describes the transition from a localized to a free carrier regime. In particular, our results show that optical bandgaps of ∼0.95 eV (optimal for carrier multiplication-facilitated solar cell power conversion) can be achieved in P−B co-doped Si NCs with D NC < D critical . These results indicate that the practical photovoltaic feasibility of co-doped Si NCs is not limited by the presence of some remaining free carriers in uncompensated NCs.

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“…Ever since the first production of impurity-doped NCs, the field has been predominantly directed toward the ability to control doping concentrations. − Plasmonic features arising from such doping can now be tuned in the near-infrared regime, in contrast to the rather fixed visible plasmon optical energies characteristic of typical noble-metal nanoparticles. , Recent investigations on doped Si NCs (the vast majority dealing with P- and B-doping configurations) show intriguing results regarding these plasmonic effects but also focus on bioimaging, , photodetector, and photovoltaic applications . Investigations on sputter-deposited doped Si NCs focused on mapping their optical band gap, solution dispersibility, and external (photo)conductivity. − In addition, plasma-produced doped Si NCs have been used to investigate localized surface plasmon resonances (LSPRs). , However, all of these efforts have been performed without a fundamental understanding of the physics governing the photoexcited e – –h + pairs, which should be subject to Coulomb-driven Auger recombination (AR) with the free carriers in these doped structures.…”

Section: Introductionmentioning

confidence: 99%

Size-Dependent Asymmetric Auger Interactions in Plasma-Produced n- and p-Type-Doped Silicon Nanocrystals

et al. 2019

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Nonradiative Auger recombination (AR) tends to dominate carrier dynamics in charged, quantum-confined structures. Consequently, it complicates the practical realization of many semiconductor nanocrystal (NC)-based devices such as light-emitting diodes, photovoltaic cells, and single-photon emitters, in which charged exciton states often occur. To this end, extensive experimental studies on direct band gap NCs have investigated the trion components (both positive and negative) that construct the total AR rate. However, such an analysis has remained elusive for indirect band gap Si NCs. In this study, we investigate AR decay of non-thermal plasma-produced n- and p-type-doped Si NCs. We expand the study over a large NC size range (D NC ≈ 3–8 nm), in which n- and p-type doping is achieved by either a substitutional or surface doping effect, respectively. First, we monitor the AR of charge-neutral multiexcitons by measuring the biexciton lifetime (τ XX ) as a function of the NC size and doping configuration. We show that this method can be used to determine the presence of free carriers for any doped NC system, regardless of the presence/absence of defect channels in the carrier dynamics. Second, we develop a photophysical fitting model to determine the Auger lifetime of the simplest charged states in Si NCs: the negative (τ X –) and positive (τ X +) trions. Trion lifetimes shorten with increasing quantum confinement, as expected from (1) closer spatial proximity of the interacting charges and (2) increased relaxation of the momentum conservation rule. While both τ X – and τ X + are in the nanosecond time regime (and both therefore completely dominate the carrier dynamics), AR with excess holes is faster. This asymmetry is explained by a higher density of valence band states in comparison to the conduction band states, due to effective mass differences between electrons and holes.

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Toward Practical Carrier Multiplication: Donor/Acceptor Codoped Si Nanocrystals in SiO₂

Cited by 13 publications

References 47 publications

Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

Critical Size for Carrier Delocalization in Doped Silicon Nanocrystals: A Study by Ultrafast Spectroscopy

Size-Dependent Asymmetric Auger Interactions in Plasma-Produced n- and p-Type-Doped Silicon Nanocrystals

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Toward Practical Carrier Multiplication: Donor/Acceptor Codoped Si Nanocrystals in SiO2

Cited by 13 publications

References 47 publications

Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

Critical Size for Carrier Delocalization in Doped Silicon Nanocrystals: A Study by Ultrafast Spectroscopy

Size-Dependent Asymmetric Auger Interactions in Plasma-Produced n- and p-Type-Doped Silicon Nanocrystals

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Toward Practical Carrier Multiplication: Donor/Acceptor Codoped Si Nanocrystals in SiO₂