Recent Progresses in Mid Infrared Nanocrystal Optoelectronics

ACS Appl. Mater. Interfaces

Notemgnou

et al. 2017

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Self-doped colloidal quantum dots (CQDs) attract a strong interest for the design of a new generation of low-cost infrared (IR) optoelectronic devices because of their tunable intraband absorption feature in the mid-IR region. However, very little remains known about their electronic structure which combines confinement and an inverted band structure, complicating the design of optimized devices. We use a combination of IR spectroscopy and photoemission to determine the absolute energy levels of HgSe CQDs with various sizes and surface chemistries. We demonstrate that the filling of the CQD states ranges from 2 electrons per CQD at small sizes (<5 nm) to more than 18 electrons per CQD at large sizes (≈20 nm). HgSe CQDs are also an interesting platform to observe vanishing confinement in colloidal nanoparticles. We present lines of evidence for a semiconductor-to-metal transition at the CQD level, through temperature-dependent absorption and transport measurements. In contrast with bulk systems, the transition is the result of the vanishing confinement rather than the increase of the doping level.

Section: Resultsmentioning

confidence: 99%

HgSe Self-Doped Nanocrystals as a Platform to Investigate the Effects of Vanishing Confinement

ACS Appl. Mater. Interfaces

Notemgnou

et al. 2017

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“…The growth of HgX CQD has been strongly improved over the recent years . However, to integrate this material in an infrared sensor, the doping in layers of HgS(e) must be well controlled.…”

Section: Discussionmentioning

confidence: 99%

“…Colloidal quantum dots (CQD) are offering an alternative platform to revisit optoelectronics while combining high performances and low fabrication cost. In addition to display and solar cell, the use of CQD for infrared optoelectronics is attracting more and more interest . To achieve narrow energy transition as those required to get absorption in the mid infrared, narrow band gap materials can be used.…”

Section: Introductionmentioning

confidence: 99%

“…To this day, HgX are the only materials to combine tunable optical features from telecom wavelengths up to the THz range with photoconductive properties. Over the last 3 years, several groups have reported the integration of HgX nanocrystals as active material for infrared detection with competitive level of performances . Recent development include new surface chemistries, the switch from photoconductor to photovoltaic or phototransistor, multispectral device, the integration of plasmonic functionalities, hybridization with graphene and even the first demonstration of mid‐IR CQD‐based focal plane array …”

Section: Introductionmentioning

confidence: 99%

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Investigation of the Self‐Doping Process in HgSe Nanocrystals

Physica Status Solidi (a)

Robin

et al. 2017

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Colloidal nanocrystals are an interesting platform for the design of low cost infrared optoelectronic materials. In addition to the conventionally observed interband features, doped nanocrystals present intraband transitions, which expand the possibilities for electronic spectrum engineering. In this paper, the recent results obtained in the field of mercury chalcogenides self-doped nanocrystals presenting absorption features in the mid infrared range are reviewed. In particular, the results relative to the synthesis, control of doping and transport properties of HgSe colloidal nanocrystals are discussed.

“…They nevertheless present a limited tunability, typically from 800 nm to 3 μm, because of PbS bulk bandgap. Mercury chalcogenides, thanks to their semimetal nature, present a wider tunability from the near IR (1 μm) up to the far IR (100 μm) . This article is dedicated to the recent developments relative to the integration of mercury chalcogenides in photovoltaic devices, especially for the short‐wave (below 2.5 μm) and mid‐wave (3–5 μm) IR.…”

Section: Introductionmentioning

confidence: 99%

Designing Photovoltaic Devices Using HgTe Nanocrystals for Short and Mid‐Wave Infrared Detection

Physica Status Solidi (a)

Chu

et al. 2019

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HgTe nanocrystals offer a unique combination of broadly tunable optical absorption in the infrared from 1 to 100 μm and photoconductive properties. Herein, some of the recent developments related to their integration into photodiodes are discussed. Concepts such as the development of colloidal unipolar barrier, development of ink to achieve strongly absorbing and conductive film, and the recent proposition of intraband photodiode are also discussed.