Nanocrystal quantum dots provide wide spectral tunability and high absorption coefficients owing to quantum confinement and large oscillator strengths, which along with solution processability, allows a facile, low cost and room temperature deposition technique. However, most solution-processed devices are plagued with high dark current densities in the order of mA/cm2, incomplete passivation, undesirable pinholes, and cracks. This, loss of control over the material morphology reduces film density, consequently lowering absorption per unit length, while simultaneously creating potential electrical shorts through the film and lowering conductivity compared to a continuous film. Amorphous-selenium detectors have gained significant attention due to their single-carrier hole impact ionization phenomenon (achieved gains ~ 1000), while exhibiting a very low excess noise factor.
We utilize the mutual advantages of both these material classes to generate a hybrid solution processed Nanocrystal/amorphous selenium device that allows spectral response over the entire electromagnetic spectrum ranging from X-rays to THz frequencies with extremely low dark/noise currents and high specific detectivity. This chalcogenide glass amorphous selenium avalanche transport layer enables the fabrication of low-cost and reliable solution processed nanocrystal devices with high specific detectivity (~ 1013 Jones), fast photoresponse with megahertz 3-dB electrical bandwidth (~ 50 Mhz), ultra-low dark current density (~ 10 pA/cm2), low noise current (~ 10 fW/Hz1/2), high linear dynamic range (~ 200 dB) and compatibility with most readout integrated circuits.
Selected Publications:
- A. Mukherjee, D. Vasileska, and A. H. Goldan, “Hole transport in selenium semiconductors using density functional theory and bulk Monte Carlo,” J. Appl. Phys., 124, 235102 (2018). Paper link