Dominik Kreil

Bio: Dominik Kreil is an academic researcher from ETH Zurich. The author has contributed to research in topics: Quantum dot & Absorption (acoustics). The author has an hindex of 1, co-authored 1 publications receiving 299 citations.

Detection of gamma photons using solution-grown single crystals of hybrid lead halide perovskites

Abstract: Cheap and sensitive gamma-ray detectors are desired for defence, medical and research applications. Solid-state gamma-radiation detectors made from solution-grown perovskites have now been demonstrated for multiple practical applications.

Ultrafast Electro‐Absorption Switching in Colloidal CdSe/CdS Core/Shell Quantum Dots Driven by Intense THz Pulses

Abstract: Next‐generation high‐speed optical networks demand the development of ultrafast optical interconnects capable of Tbit s−1 data rates. By utilizing colloidal CdSe/CdS core/shell quantum dots, gated by intense THz pulses, a proof of concept of an all‐optical femtosecond electro‐absorption switch is presented in this work. Without any additional enhancement of the THz electric field, an extinction contrast of more than 6 dB and transmission changes in the visible of more than 15% are achieved, with the latter setting a new record for solution‐processed electro‐absorption materials at room temperature. The absence of physical artifacts, originating from electrodes and field enhancing structures, allows to employ a simple and intuitive numerical model, which rationalizes the large field‐induced electro‐absorption response. Supported by theoretical calculations, the importance of the energy band alignment of heterostructure quantum dots are discussed for the first time and suggest that further improvement of the modulation depth and contrast may be achieved with Type‐II quantum dots.

Dependence of a direct THz driven Stark effect on the energy band alignment in heterostructure Quantum Dots

Abstract: We report on direct ultrafast electro-absorption switching in colloidal CdSe/CdS core/shell quantum dots driven by intense THz pulses without a field enhancing structure, and suggest a route to optimize electro-absorption modulators with respect to the energy band alignment of the heterostructure material.

Direct THz field driven electro-absorption modulation in heterostructure quantum dots

Abstract: We report on electro-absorption switching in colloidal CdSe/CdS core/shell quantum dots, gated by intense THz pulses, without field enhancing structures, and suggest a route to optimize electro-absorption modulators with respect to the energy band alignment of the heterostructure material.

High efficiency planar-type perovskite solar cells with negligible hysteresis using EDTA-complexed SnO2

Abstract: Even though the mesoporous-type perovskite solar cell (PSC) is known for high efficiency, its planar-type counterpart exhibits lower efficiency and hysteretic response. Herein, we report success in suppressing hysteresis and record efficiency for planar-type devices using EDTA-complexed tin oxide (SnO2) electron-transport layer. The Fermi level of EDTA-complexed SnO2 is better matched with the conduction band of perovskite, leading to high open-circuit voltage. Its electron mobility is about three times larger than that of the SnO2. The record power conversion efficiency of planar-type PSCs with EDTA-complexed SnO2 increases to 21.60% (certified at 21.52% by Newport) with negligible hysteresis. Meanwhile, the low-temperature processed EDTA-complexed SnO2 enables 18.28% efficiency for a flexible device. Moreover, the unsealed PSCs with EDTA-complexed SnO2 degrade only by 8% exposed in an ambient atmosphere after 2880 h, and only by 14% after 120 h under irradiation at 100 mW cm−2. The development of high efficiency planar-type perovskite solar cell has been lagging behind the mesoporous-type counterpart. Here Yang et al. modify the oxide based electron transporting layer with organic acid and obtain planar-type cells with high certified efficiency of 21.5% and decent stability.

Cs 2 AgBiBr 6 single-crystal X-ray detectors with a low detection limit

Abstract: Sensitive X-ray detection is crucial for medical diagnosis, industrial inspection and scientific research. The recently described hybrid lead halide perovskites have demonstrated low-cost fabrication and outstanding performance for direct X-ray detection, but they all contain toxic Pb in a soluble form. Here, we report sensitive X-ray detectors using solution-processed double perovskite Cs2AgBiBr6 single crystals. Through thermal annealing and surface treatment, we largely eliminate Ag+/Bi3+ disordering and improve the crystal resistivity, resulting in a detector with a minimum detectable dose rate as low as 59.7 nGyair s−1, comparable to the latest record of 0.036 μGyair s−1 using CH3NH3PbBr3 single crystals. Suppressed ion migration in Cs2AgBiBr6 permits relatively large external bias, guaranteeing efficient charge collection without a substantial increase in noise current and thus enabling the low detection limit. Double perovskite Cs2AgBiBr6 single crystals are used to make a sensitive X-ray detector. The device exhibits a high sensitivity of 105 µC Gyair −1 cm−2 and a low detection limit of 59.7 nGyairs−1, and demonstrates long-term operational stability.

Printable organometallic perovskite enables large-area, low-dose X-ray imaging

Abstract: Medical X-ray imaging procedures require digital flat detectors operating at low doses to reduce radiation health risks. Solution-processed organic-inorganic hybrid perovskites have characteristics that make them good candidates for the photoconductive layer of such sensitive detectors. However, such detectors have not yet been built on thin-film transistor arrays because it has been difficult to prepare thick perovskite films (more than a few hundred micrometres) over large areas (a detector is typically 50 centimetres by 50 centimetres). We report here an all-solution-based (in contrast to conventional vacuum processing) synthetic route to producing printable polycrystalline perovskites with sharply faceted large grains having morphologies and optoelectronic properties comparable to those of single crystals. High sensitivities of up to 11 microcoulombs per air KERMA of milligray per square centimetre (μC mGyair-1 cm-2) are achieved under irradiation with a 100-kilovolt bremsstrahlung source, which are at least one order of magnitude higher than the sensitivities achieved with currently used amorphous selenium or thallium-doped cesium iodide detectors. We demonstrate X-ray imaging in a conventional thin-film transistor substrate by embedding an 830-micrometre-thick perovskite film and an additional two interlayers of polymer/perovskite composites to provide conformal interfaces between perovskite films and electrodes that control dark currents and temporal charge carrier transportation. Such an all-solution-based perovskite detector could enable low-dose X-ray imaging, and could also be used in photoconductive devices for radiation imaging, sensing and energy harvesting.

Perovskite-based photodetectors: materials and devices

Abstract: While the field of perovskite-based optoelectronics has mostly been dominated by photovoltaics, light-emitting diodes, and transistors, semiconducting properties peculiar to perovskites make them interesting candidates for innovative and disruptive applications in light signal detection. Perovskites combine effective light absorption in the broadband range with good photo-generation yield and high charge carrier mobility, a combination that provides promising potential for exploiting sensitive and fast photodetectors that are targeted for image sensing, optical communication, environmental monitoring or chemical/biological detection. Currently, organic–inorganic hybrid and all-inorganic halide perovskites with controlled morphologies of polycrystalline thin films, nano-particles/wires/sheets, and bulk single crystals have shown key figure-of-merit features in terms of their responsivity, detectivity, noise equivalent power, linear dynamic range, and response speed. The sensing region has been covered from ultraviolet-visible-near infrared (UV-Vis-NIR) to gamma photons based on two- or three-terminal device architectures. Diverse photoactive materials and devices with superior optoelectronic performances have stimulated attention from researchers in multidisciplinary areas. In this review, we provide a comprehensive overview of the recent progress of perovskite-based photodetectors focusing on versatile compositions, structures, and morphologies of constituent materials, and diverse device architectures toward the superior performance metrics. Combining the advantages of both organic semiconductors (facile solution processability) and inorganic semiconductors (high charge carrier mobility), perovskites are expected to replace commercial silicon for future photodetection applications.

Monolithic integration of hybrid perovskite single crystals with heterogenous substrate for highly sensitive X-ray imaging

Abstract: Hybrid perovskite crystals are integrated onto silicon wafers enabling fabrication of an X-ray linear detector array. High sensitivity may reduce patient dose in medical imaging applications.