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G.J. Adriaenssens

Bio: G.J. Adriaenssens is an academic researcher from Katholieke Universiteit Leuven. The author has contributed to research in topics: Photoconductivity & Density of states. The author has an hindex of 19, co-authored 86 publications receiving 1337 citations. Previous affiliations of G.J. Adriaenssens include Pierre-and-Marie-Curie University.


Papers
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TL;DR: In this paper, an analytic expression for the effective transport energy in a positionally random and energetically disordered hopping system is obtained, and it is shown that multiple carrier jumps within pairs of occasionally close localized states strongly affect the position of the effective transportation level on the energy scale.
Abstract: An analytic expression for the effective transport energy in a positionally random and energetically disordered hopping system is obtained. It is shown that multiple carrier jumps within pairs of occasionally close localized states strongly affect the position of the effective transport level on the energy scale and lead to a noticeable difference between the effective transport energy and the energy of most probable jumps. In a hopping system with a Gaussian density-of-states energy distribution, the equilibrium carrier mobility is found to be an almost factorized function of temperature and concentration of localized states.

130 citations

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TL;DR: In this paper, the structure and defects in detonation synthesis of ultradisperse diamond (UDD) powders are analyzed in terms of the different structure of the shell of UDD particles, produced under different conditions.

127 citations

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TL;DR: In this paper, the properties of hydrogenated amorphous silicon (a-Si:H) deposited at very high growth rates (6-80 nm/s) by means of a remote H2-SiH4 plasma have been investigated as a function of the H2 flow in the Ar-H2 operated plasma source.
Abstract: The properties of hydrogenated amorphous silicon (a-Si:H) deposited at very high growth rates (6–80 nm/s) by means of a remote Ar–H2–SiH4 plasma have been investigated as a function of the H2 flow in the Ar–H2 operated plasma source. Both the structural and optoelectronic properties of the films improve with increasing H2 flow, and a-Si:H suitable for the application in solar cells has been obtained at deposition rates of 10 nm/s for high H2 flows and a substrate temperature of 400 °C. The “optimized” material has a hole drift mobility which is about a factor of 10 higher than for standard a-Si:H. The electron drift mobility, however, is slightly lower than for standard a-Si:H. Furthermore, preliminary results on solar cells with intrinsic a-Si:H deposited at 7 nm/s are presented. Relating the film properties to the SiH4 dissociation reactions reveals that optimum film quality is obtained for conditions where H from the plasma source governs SiH4 dissociation and where SiH3 contributes dominantly to film ...

106 citations

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TL;DR: In this paper, the post-transit current was shown to be the Laplace transform of the density of states in a time-of-flight experiment on hydrogenated amorphous silicon.
Abstract: We use the post-transit photocurrent in a time-of-flight experiment for spectroscopic purposes. It is shown, within the multiple-trapping framework, that the post-transit current is the Laplace transform of the density of states. A simple inversion procedure is suggested and is shown to be quite adequate provided the gap-state distribution does not vary too strongly with energy. The method has been applied to hydrogenated amorphous silicon. Experimental evidence shows that the post-transit photocurrent truly reflects the release out of deeper-lying traps and is not a consequence of nonuniform, time-dependent fields, contact-related properties, or injection phenomena. The measured ${\ensuremath{\mu}}_{0}$${\ensuremath{\tau}}_{d}$ are compatible with the deconvoluted density of states. A comparative discussion of our results with other published data obtained with conventional methods like the field-effect, space-charge-limited current, and deep-level transient spectroscopy techniques is given.

102 citations

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TL;DR: In this paper, a concept of random spatial fluctuations in the potential landscape of disordered semiconductors is employed to explain the effect of suppressed charge carrier recombination in these materials, and the rate of bimolecular recombination is anomalously low due to spatial separation of electrons and holes in the fluctuating potential landscape.

76 citations


Cited by
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TL;DR: This review is a critical account of the interrelation between MHP electronic structure, absorption, emission, carrier dynamics and transport, and other relevant photophysical processes that have propelled these materials to the forefront of modern optoelectronics research.
Abstract: A new chapter in the long and distinguished history of perovskites is being written with the breakthrough success of metal halide perovskites (MHPs) as solution-processed photovoltaic (PV) absorbers. The current surge in MHP research has largely arisen out of their rapid progress in PV devices; however, these materials are potentially suitable for a diverse array of optoelectronic applications. Like oxide perovskites, MHPs have ABX3 stoichiometry, where A and B are cations and X is a halide anion. Here, the underlying physical and photophysical properties of inorganic (A = inorganic) and hybrid organic–inorganic (A = organic) MHPs are reviewed with an eye toward their potential application in emerging optoelectronic technologies. Significant attention is given to the prototypical compound methylammonium lead iodide (CH3NH3PbI3) due to the preponderance of experimental and theoretical studies surrounding this material. We also discuss other salient MHP systems, including 2-dimensional compounds, where rele...

1,125 citations

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TL;DR: In this paper, a review of chalcogenide glasses and the current status of their applications is given, and the possibilities of fabricating active devices, such as fiber amplifiers and lasers, are presented.
Abstract: A review of some properties of chalcogenide glasses and the current status of their applications is given. Techniques to characterize the linear and non-linear properties of these glasses are introduced and used to measure the optical constants of chalcogenide glasses in the form of bulk, thin film and fiber. Different techniques for the fabrication of gratings and waveguides in these glasses are described. Achievable efficiencies of gratings, as well as propagation losses of fabricated waveguides, are presented. The possibilities of fabricating active devices, such as fiber amplifiers and lasers, are presented. Finally, a novel application of chalcogenide glasses, namely all-optical switching for the fabrication of efficient femtosecond switches, is introduced.

1,001 citations

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TL;DR: The radiative efficiency for hybrid lead halide perovskite films is examined and it is found that if high efficiencies are to be obtained for intermediate charge-carrier densities (n ≈ 10(14) cm(-3)) trap-related recombination lifetimes will have to be enhanced well into the microsecond range, and the radiative efficiencies that may be obtained are evaluated.
Abstract: Photovoltaic (PV) devices that harvest the energy provided by the sun have great potential as renewable energy sources, yet uptake has been hampered by the increased cost of solar electricity compared with fossil fuels. Hybrid metal halide perovskites have recently emerged as low-cost active materials in PV cells with power conversion efficiencies now exceeding 20%. Rapid progress has been achieved over only a few years through improvements in materials processing and device design. In addition, hybrid perovskites appear to be good light emitters under certain conditions, raising the prospect of applications in low-cost light-emitting diodes and lasers. Further optimization of such hybrid perovskite devices now needs to be supported by a better understanding of how light is converted into electrical currents and vice versa. This Account provides an overview of charge-carrier recombination and mobility mechanisms encountered in such materials. Optical-pump-terahertz-probe (OPTP) photoconductivity spectroscopy is an ideal tool here, because it allows the dynamics of mobile charge carriers inside the perovskite to be monitored following excitation with a short laser pulse whose photon energy falls into the range of the solar spectrum. We first review our insights gained from transient OPTP and photoluminescence spectroscopy on the mechanisms dominating charge-carrier recombination in these materials. We discuss that mono-molecular charge-recombination predominantly originates from trapping of charges, with trap depths being relatively shallow (tens of millielectronvolts) for hybrid lead iodide perovskites. Bimolecular recombination arises from direct band-to-band electron-hole recombination and is found to be in significant violation of the simple Langevin model. Auger recombination exhibits links with electronic band structure, in accordance with its requirement for energy and momentum conservation for all charges involved. We further discuss charge-carrier mobility values extracted from OPTP measurements and their dependence on perovskite composition and morphology. The significance of the reviewed charge-carrier recombination and mobility parameters is subsequently evaluated in terms of the charge-carrier diffusion lengths and radiative efficiencies that may be obtained for such hybrid perovskites. We particularly focus on calculating such quantities in the limit of ultra-low trap-related recombination, which has not yet been demonstrated but could be reached through further advances in material processing. We find that for thin films of hybrid lead iodide perovskites with typical charge-carrier mobilities of ∼30cm(2)/(V s), charge-carrier diffusion lengths at solar (AM1.5) irradiation are unlikely to exceed ∼10 μm even if all trap-related recombination is eliminated. We further examine the radiative efficiency for hybrid lead halide perovskite films and show that if high efficiencies are to be obtained for intermediate charge-carrier densities (n ≈ 10(14) cm(-3)) trap-related recombination lifetimes will have to be enhanced well into the microsecond range.

792 citations

Journal ArticleDOI
TL;DR: An overview of the physical function of organic solar cells, their state-of-the-art performance and limitations, as well as novel concepts to achieve a better material stability and higher power conversion efficiencies are presented in this paper.
Abstract: Organic solar cells have the potential to be low-cost and efficient solar energy converters, with a promising energy balance. They are made of carbon-based semiconductors, which exhibit favourable light absorption and charge generation properties, and can be manufactured by low temperature processes such as printing from solvent-based inks, which are compatible with flexible plastic substrates or even paper. In this review, we will present an overview of the physical function of organic solar cells, their state-of-the-art performance and limitations, as well as novel concepts to achieve a better material stability and higher power conversion efficiencies. We will also briefly review processing and cost in view of the market potential.

737 citations

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TL;DR: The impact of increasing the CT energy-in order to raise the open circuit voltage, but lowering the kinetic excess energy of the CT complexes at the same time-on the charge photogeneration will be discussed.
Abstract: Charge transfer complexes are interfacial charge pairs residing at the donor-acceptor heterointerface in organic solar cell. Experimental evidence shows that it is crucial for the photovoltaic performance, as both photocurrent and open circuit voltage directly depend on it. For charge photogeneration, charge transfer complexes represent the intermediate but essential step between exciton dissotiation and charge extraction. Recombination of free charges to the ground state is via the bound charge transfer state before being lost to the ground state. In terms of the open circuit voltage, its maximum achievable value is determined by the energy of the charge transfer state. An important question is whether or not maximum photocurrent and maximum open circuit voltage can be achieved simultaneously. The impact of increasing the CT energy-in order to raise the open circuit voltage, but lowering the kinetic excess energy of the CT complexes at the same time-on the charge photogeneration will accordingly be discussed. Clearly, the fundamental understanding of the processes involving the charge transfer state is essential for an optimisation of the performance of organic solar cells.

681 citations