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

83 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

Fingerprint

Photodiodes
p-n junctions
Quantum efficiency
Nanocrystals
Semiconductor quantum dots
photodiodes
quantum efficiency
nanocrystals
quantum dots
Dark currents
sensitivity
Photodetectors
optoelectronic devices
dark current
Conduction bands
cells
Photocurrents
Optoelectronic devices
Oxides
Light emitting diodes

Keywords

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

ASJC Scopus subject areas

  • Biomaterials
  • Electrochemistry
  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

High-Sensitivity p-n junction photodiodes based on Pbs nanocrystal quantum dots. / Pal, Bhola N.; Robel, Istvan; Mohite, Aditya; Laocharoensuk, Rawiwan; Werder, Donald J.; Klimov, Victor I.

In: Advanced Functional Materials, Vol. 22, No. 8, 24.04.2012, p. 1741-1748.

Research output: Contribution to journalArticle

Pal, Bhola N. ; Robel, Istvan ; Mohite, Aditya ; Laocharoensuk, Rawiwan ; Werder, Donald J. ; Klimov, Victor I. / High-Sensitivity p-n junction photodiodes based on Pbs nanocrystal quantum dots. In: Advanced Functional Materials. 2012 ; Vol. 22, No. 8. pp. 1741-1748.
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