Research Update:Structure/Property Relations in “Giant” Semiconductor Nanocrystals: Opportunities in Photonics and Electronics


Recently Dr. Fabiola Navarro-Pardo, the post-doctor of institute of fundemental and frontier science (IFFS), has published an article titled “Structure/Property Relations in “Giant” Semiconductor Nanocrystals: Opportunities in Photonics and Electronics” in  Accounts of Chemical Research. Institute of fundemental and frontier science (IFFS) is the first author affiliation and Dr. Haiguang Zhao, Prof. Zhiming Wang and Prof. Federico Rosei are corresponding authors.

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Semiconductor nanocrystals exhibit size-tunable absorption and emission ranging from the ultraviolet (UV) to the near-infrared (NIR) spectral range, high absorption coefficient, and high photoluminescence quantum yield. Effective surface passivation of these so-called quantum dots (QDs) may be achieved by growing a shell of another semiconductor material. The resulting core/shell QDs can be considered as a model system to study and optimize structure/property relations. A special case consists in growing thick shells (1.5 up to few tens of nanometers) to produce “giant” QDs (g-QDs). Tailoring the chemical composition and structure of CdSe/CdS and PbS/CdS g-QDs is a promising approach to widen the spectral separation of absorption and emission spectra (i.e., the Stokes shift), improve the isolation of photogenerated carriers from surface defects and enhance charge carrier lifetime and mobility. However, most stable systems are limited by a thick CdS shell, which strongly absorbs radiation below 500 nm, covering the UV and part of the visible range. Modification of the interfacial region between the core and shell of g-QDs or tuning their doping with narrow band gap semiconductors are effective approaches to circumvent this challenge. In addition, the synthesis of g-QDs composed of environmentally friendly elements (e.g., CuInSe2/CuInS2) represents an alternative to extend their absorption into the NIR range. Additionally, the band gap and band alignment of g-QDs can be engineered by proper selection of the constituents according to their band edge positions and by tuning their stoichiometry during wet chemical synthesis. In most cases, the quasi-type II localization regime of electrons and holes is achieved. In this type of g-QDs, electrons can leak into the shell region, while the holes remain confined within the core region. This electron–hole spatial distribution is advantageous for optoelectronic devices, resulting in efficient electron–hole separation while maintaining good stability.

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