Microwave-Polyol Synthesis of Sub-10-nm PbS Nanocrystals for Metal Oxide/Nanocrystal Heterojunction Photodetectors

Paliwal, A and Singh, SV and Sharma, A and Sugathan, A and Liu, S-W and Biring, S and Pal, BN (2018) Microwave-Polyol Synthesis of Sub-10-nm PbS Nanocrystals for Metal Oxide/Nanocrystal Heterojunction Photodetectors. In: ACS Applied Nano Materials, 1 (11). pp. 6063-6072.

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Abstract

A rapid microwave-polyol technique is developed to grow bare-surface sub-10-nm lead sulfide (PbS) colloidal nanocrystals (NCs) of uniform size. Growth involves three distinct dynamical stages. PbS NCs homogeneously nucleate and undergo a fast growth process that spontaneously aggregates them into a continuous microstructure of PbS. Next, the interaction of low-power microwave irradiation with the NCs' dipole moments along different crystallographic axes leads to the development of strain at the NCs' grain boundaries, which ultimately causes dissociation of the aggregated microstructures into individual uniform-sized PbS NCs. The most distinctive feature of this growth technique is the bare nature and uniform size of the NCs produced. This gives the freedom to fabricate a highly packed NC thin film, which is essential for enhanced charge-transport properties. It simultaneously also precludes the need of undergoing a detrimental solid-state ligand-exchange process, which is indispensably required for casting thin films from conventional counterpart long-aliphatic-ligand-capped NCs. To realize the photosensitivity and charge-transport nature of these microwave-synthesized NCs, we fabricated a lateral heterojunction photoconductor and a phototransistor that work on the principal of electron transfer to the metal oxide layer. The photoconductor exhibits prominent multispectral photosensitivity in the visible region, demonstrating high external quantum efficiency and detectivity of 7.42 × 102% and 1.07 × 1011 jones, respectively. Further, it also shows superior photocurrent generation with respect to the conventional hot-injection-method-synthesized PbS NC-based photoconductor, indicating more efficient inter-NC charge transport in its NC thin film. The unencapsulated photoconductor exhibits a long air-storage lifetime, which reflects air stability of the device and PbS NCs. In addition to the photoconductor, the metal oxide/PbS heterojunction phototransistor also shows superior photosensitivity with a responsivity and a response time of 3 × 10-2A/W and 2.2 s, respectively.

Item Type:	Journal Article
Publication:	ACS Applied Nano Materials
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to the American Chemical Society.
Keywords:	Alcohols; Carrier transport; Grain boundaries; Heterojunctions; IV-VI semiconductors; Ligands; Light sensitive materials; Metals; Microstructure; Microwave irradiation; Nanocrystals; Photodetectors; Photons; Phototransistors; Quantum efficiency; Semiconductor quantum dots; Sols; Sulfur compounds; Thin films, Colloidal quantum dots; Detectivity; External quantum efficiency; Heterojunction photodetectors; Heterojunction phototransistors; Microwave synthesis; P-n heterojunctions; Photocurrent generations, Lead compounds
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	02 Aug 2022 11:49
Last Modified:	02 Aug 2022 11:49
URI:	https://eprints.iisc.ac.in/id/eprint/75137

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