High-Sensitivity p-n junction photodiodes based on Pbs nanocrystal quantum dots

Bhola N. Pal, Istvan Robel, Aditya Mohite, Rawiwan Laocharoensuk, Donald J. Werder, Victor I. Klimov

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

Chemically synthesized nanocrystal quantum dots (NQDs) are promising materials for applications in solution-processable optoelectronic devices such as light emitting diodes, photodetectors, and solar cells. Here, we fabricate and study two types of p-n junction photodiodes in which the photoactive p-layer is made from PbS NQDs while the transparent n-layer is fabricated from wide bandgap oxides (ZnO or TiO 2). By using a p-n junction architecture we are able to significantly reduce the dark current compared to earlier Schottky junction devices without reducing external quantum efficiency (EQE), which reaches values of up to ∼80%. The use of this device architecture also allows us to significantly reduce noise and obtain high detectivity (>10 12 cm Hz 1/2 W -1) extending to the near infrared past 1 μm. We observe that the spectral shape of the photoresponse exhibits a significant dependence on applied bias, and specifically, the EQE sharply increases around 500-600 nm at reverse biases greater than 1 V. We attribute this behavior to a "turn-on" of an additional contribution to the photocurrent due to electrons excited to the conduction band from the occupied mid-gap states.

Original languageEnglish
Pages (from-to)1741-1748
Number of pages8
JournalAdvanced Functional Materials
Volume22
Issue number8
DOIs
Publication statusPublished - Apr 24 2012

Keywords

  • PbS
  • detectivity
  • mid-gap band
  • nanocrystal quantum dot
  • p-n junction
  • photodetector

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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