Quantum dots: time of growth and change: Page 5 of 6

July 27, 2018 //By Dr Khasha Ghaffarzadeh
Quantum dots: time of growth and change
Quantum dots (QDs) are no longer a young technology. Even their commercialization process is not new since the pioneering companies were formed in the 2001-2005 period. The QDs are also not commercially novice: they have been employed in LCD displays as remote phosphors for several years.  

QDs in lighting

Lighting is an attractive application not least because lighting is the largest application for LEDs. Here, the driver in the general lighting sector is to increase CRI of LED lights without sacrificing efficiency. This can be made possible with the narrow FWHM of QDs. This industry will make further progress as cost fall and, more crucially, as QDs become more stable enabling integration into more types of LEDs.

Prior to that however, companies have proposed film-type QDs to optimize the emission light. However, market response has thus far been lukewarm. In parallel, some seek to deploy QD lights in specialize applications as horticulture in which QDs are used to fine-tune the emission spectra.  

 

QDs in sensors

Sensors are also a promising proposition. Here, the focus is on QDs' broad absorption characteristics. We can divide the work into two categories: visible and IR/NIR image sensors. In the former, QDs can be cast onto silicon read-out circuits to enable high resolution (small pixel) and highly sensitive images sensors with a global shutter and a large pixel capacitor.

This hybrid QD-Si sensor is made possible because of the high sensitivity of the QD layer (if properly fused) and its ability to separate the photosensitive and processing circuits. In the latter approach (IR/NIR sensor), the right QD chemistry (e.g., PbS) can tune the absorption spectra to be sensitive to NI/IR. The QDs can also be added directly on the Si read-out circuit. As such, there will not need to un-monolithic integration of different semiconductor systems with silicon, limiting resolution.


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