Efficient detection of UV light by quantum dots sensitized silicon detector

Open Access
Thakur, Yash
Graduate Program:
Electrical Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 30, 2014
Committee Members:
  • Jerzy Ruzyllo, Thesis Advisor
  • Noel Christopher Giebink, Thesis Advisor
  • ultraviolet
  • quantum dots
  • downshifting
  • detector
  • CdSe/ZnS
  • mist deposition
Historically, light coming from the sun has been our prime source of light energy. It is crucial for various applications to detect and utilize the invisible part beyond violet. The detection of ultraviolet (UV) radiation has been of great interest for industrial, medical, military, and environmental applications. Therefore, it is important to make simple, accurate, reliable, and low cost instruments to detect UV. Silicon detectors are the most common and inexpensive commercial solutions available for UV detection. However, they show poor performance in ultraviolet region. In this thesis, the red CdSe/ZnS core-shell quantum dots are used to improve the response of the silicon detector by downshifting the UV light to peak sensitive wavelength of silicon. In this study, an improvement in average external quantum efficiency of 51% in the near UV (300-400 nm) region has been confirmed using a 40 nm thick layer of CdSe/ZnS quantum dots. The short circuit current is improved by a factor of 6 under laser excitation of 405 nm. CdSe/ZnS core-shell quantum dots were chosen for this study because of their direct band gap and size tunable wavelength properties, which span over the entire visible spectrum. The size selection of the quantum dots was based on emission wavelength. The ultra-thin layer of quantum dots has been deposited using the mist deposition tool. The results demonstrate that the quantum dots can be used as an alternative to phosphors for down-shifting the ultra violet light in silicon UV detectors.