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Theses

Colloidal semiconductor nanocrystals for optoelectronic applications : photodetectors and light emitting diodes

Abstract : Nanocrystals with a dimension below their excitonic Bohr radius can provide size-tunable optoelectronic properties, enabling on-demand tailoring of properties for specific applications. Especially, the advance of wet chemistry synthesis of colloidal nanocrystals makes them promising building blocks for the next-generation solution-processible low-cost optoelectronics such as light emitting, sensing, and harvesting. My thesis targets two aspects of the nanocrystal-based devices: infrared (IR) photodetector and light emitting diode (LED). My thesis is first focused on the heavy-metal-free IR photodetection using the intraband transition of self-doped Ag2Se or the plasmonic resonance of remotely doped ITO (tin doped indium oxide) nanocrystals. Before integrating them to photoconductive devices, I study their optical and transport properties as well as their energy spectra. I then test their IR photodetection performance and rationalize their weak performance compared with their heavy metal counterparts. In the second part of my thesis, I advance to the all-solution nanocrystal-based LEDs in the visible and SWIR, with an emphasis on their practical applications. The designed visible LED using CdSe/CdZnS nanoplatelets (NPLs) shows the lowest turn-on voltage and the longest lifetime for NPL-based LED. I also provide insights on the origin of efficiency droop. Then, this LED is coupled with a homemade PbS broadband photodetector to achieve, for the first time, an all-nanocrystal based LiFi-like communication setup. For SWIR LEDs, HgTe is used as IR emitter. By forming a HgTe/ZnO bulk heterojunction in the emitting layer, a bright SWIR LED capable of active imaging is obtained.
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Submitted on : Friday, July 16, 2021 - 4:17:11 PM
Last modification on : Saturday, July 17, 2021 - 3:47:30 AM

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  • HAL Id : tel-03289105, version 1

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Junling Qu. Colloidal semiconductor nanocrystals for optoelectronic applications : photodetectors and light emitting diodes. Cristallography. Sorbonne Université, 2021. English. ⟨NNT : 2021SORUS021⟩. ⟨tel-03289105⟩

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