Chemical Tailoring of Band Offsets at the Interface of ZnSe-CdS Heterostructures for Delocalized Photoexcited Charge Carriers

Dalui, Amit and Chakraborty, Arup and Thupakula, Umamahesh and Khan, Ali Hossain and Sengupta, Sucheta and Satpati, Biswarup and Sarma, DD and Dasgupta, Indra and Acharya, Somobrata (2016) Chemical Tailoring of Band Offsets at the Interface of ZnSe-CdS Heterostructures for Delocalized Photoexcited Charge Carriers. In: JOURNAL OF PHYSICAL CHEMISTRY C, 120 (19). pp. 10118-10128.

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Abstract

Monocomponent quantum dots (QDs) possess limited electron-hole delocalization capacity upon photoexcitation that suppresses the efficiency of photoenergy harvesting devices. Type II heterostructures offer band offsets at conduction and valence bands depending upon the band gaps of the constituent QDs which largely depend on their sizes. Hence, by keeping the size of one constituent QD fixed while varying the size of the other QD selectively, the band offsets at the interface can be engineered selectively. We report on the tuning of band offsets by synthesizing component size modulated heterostructures composed of a fixed sized ZnSe QD and size tuned CdS QDs with variable band gaps. The resultant heterostructures show spontaneous charge carrier separation across the interface upon photoexcitation depending on the extent of band offsets. Formation mechanism, epitaxial relationship, and the intrinsic nature of interface of the heterostructures are investigated. Experimental results are corroborated with ab initio electronic structure calculations based on density functional theory. Spontaneous charge carrier delocalization across the interface depends on the magnitude of band offsets, which facilitates fabrication of QD sensitized solar cells (QDSSCs). Improved device performances of QDSSCs in comparison to the limited photon-to-current conversion efficiencies of monocomponent QDs demonstrates the significance of band offsets for natural charge carrier separation.

Item Type:	Journal Article
Publication:	JOURNAL OF PHYSICAL CHEMISTRY C
Publisher:	AMER CHEMICAL SOC
Additional Information:	Copy right for this article belongs to the AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	22 Jun 2016 06:02
Last Modified:	22 Jun 2016 06:02
URI:	http://eprints.iisc.ac.in/id/eprint/54048

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