Open Access Nano Express

Effective harvesting, detection, and conversion of IR radiation due to quantum dots with built-in charge

Kimberly Sablon1, Andrei Sergeev2, Nizami Vagidov2, Andrei Antipov2, John Little1 and Vladimir Mitin2*

Author Affiliations

1 U.S. Army Research Laboratory, Powder Mill Road, Adelphi, MD, 20783-1197, USA

2 University at Buffalo, State University of New York, Buffalo, NY, 14260-1920, USA

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Nanoscale Research Letters 2011, 6:584  doi:10.1186/1556-276X-6-584

Published: 7 November 2011

Abstract

We analyze the effect of doping on photoelectron kinetics in quantum dot [QD] structures and find two strong effects of the built-in-dot charge. First, the built-in-dot charge enhances the infrared [IR] transitions in QD structures. This effect significantly increases electron coupling to IR radiation and improves harvesting of the IR power in QD solar cells. Second, the built-in charge creates potential barriers around dots, and these barriers strongly suppress capture processes for photocarriers of the same sign as the built-in-dot charge. The second effect exponentially increases the photoelectron lifetime in unipolar devices, such as IR photodetectors. In bipolar devices, such as solar cells, the solar radiation creates the built-in-dot charge that equates the electron and hole capture rates. By providing additional charge to QDs, the appropriate doping can significantly suppress the capture and recombination processes via QDs. These improvements of IR absorption and photocarrier kinetics radically increase the responsivity of IR photodetectors and photovoltaic efficiency of QD solar cells.

Keywords:
quantum dot; infrared photodetector; solar cell; photoresponse; doping; potential barrier; capture processes