TY  - JOUR
A1  - Kiermasch, David
A1  - Fischer, Mathias
A1  - Gil-Escrig, Lidón
A1  - Baumann, Andreas
A1  - Bolink, Henk J.
A1  - Dyakonov, Vladimir
A1  - Tvingstedt, Kristofer
T1  - Reduced Recombination Losses in Evaporated Perovskite Solar Cells by Postfabrication Treatment
JF  - Solar RRL
N2  - The photovoltaic perovskite research community has now developed a large set of tools and techniques to improve the power conversion efficiency (PCE). One such arcane trick is to allow the finished devices to dwell in time, and the PCE often improves. Herein, a mild postannealing procedure is implemented on coevaporated perovskite solar cells confirming a substantial PCE improvement, mainly attributed to an increased open-circuit voltage (V\(_{OC}\)). From a V\(_{OC}\) of around 1.11 V directly after preparation, the voltage improves to more than 1.18 V by temporal and thermal annealing. To clarify the origin of this annealing effect, an in-depth device experimental and simulation characterization is conducted. A simultaneous reduction of the dark saturation current, the ideality factor (n\(_{id}\)), and the leakage current is revealed, signifying a substantial impact of the postannealing procedure on recombination losses. To investigate the carrier dynamics in more detail, a set of transient optoelectrical methods is first evaluated, ascertaining that the bulk carrier lifetime is increased with device annealing. Second, a drift-diffusion simulation is used, confirming that the beneficial effect of the annealing has its origin in effective bulk trap passivation that accordingly leads to a reduction of Shockley–Read–Hall recombination rates.
KW  - defects
KW  - heating
KW  - lifetimes
KW  - passivation
KW  - perovskite solar cells
KW  - recombination
KW  - Shockley–Read–Hall
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258003
VL  - 5
IS  - 11
ER  - 
TY  - JOUR
A1  - Fuchs, F.
A1  - Stender, B.
A1  - Trupke, M.
A1  - Simin, D.
A1  - Pflaum, J.
A1  - Dyakonov, V.
A1  - Astakhov, G.V.
T1  - Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide
JF  - Nature Communications
N2  - Vacancy-related centres in silicon carbide are attracting growing attention because of their appealing optical and spin properties. These atomic-scale defects can be created using electron or neutron irradiation; however, their precise engineering has not been demonstrated yet. Here, silicon vacancies are generated in a nuclear reactor and their density is controlled over eight orders of magnitude within an accuracy down to a single vacancy level. An isolated silicon vacancy serves as a near-infrared photostable single-photon emitter, operating even at room temperature. The vacancy spins can be manipulated using an optically detected magnetic resonance technique, and we determine the transition rates and absorption cross-section, describing the intensity-dependent photophysics of these emitters. The on-demand engineering of optically active spins in technologically friendly materials is a crucial step toward implementation of both maser amplifiers, requiring high-density spin ensembles, and qubits based on single spins.
KW  - nuclear magnetic resonance
KW  - coherent control
KW  - 4H
KW  - phosphorus
KW  - qubits
KW  - defects
KW  - entanglement
KW  - room temperature
KW  - vacancy
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148502
VL  - 6
IS  - 7578
ER  -