Executive Summary : | Shortwave infrared (SWIR) (1000-1700 nm) light emitters gain widespread interest due to their use in a range of potential applications like communications, 3D imaging, bio-imaging, Internet of Things (IoT) embedded devices, augmented reality, machine vision, environment, food and pharmaceutical industry, car sensors, surveillance, spectrometer etc. Currently, the most of SWIR light emitters available in the market are light emitting diodes (LEDs) or lasers based on III-V semiconductors, mainly InGaAs and InGaAsP which are mostly complementary metal oxide semiconductor (CMOS) incompatible and fabricated with expensive deposition techniques. Thus, developing low-cost, smart device compatible SWIR light emitters can revolutionize the new generation SWIR light source based smart devices. Colloidal quantum dots (CQDs) can be an attractive choice for efficient SWIR light emitters due to their unique property of bandgap tuning with quantum confinement, solution process capability, large-scale production capability, CMOS compatibility. Light emitters based on CQDs in visible range has already shown commendable success and in some cases are on the verge of commercialization. Their SWIR counterparts are suffering from low performance mainly due to lower radiative recombination probability (also known as photoluminescence quantum yield (PLQY)) in the active layer. Over the years several efforts have been done to improve the performance of SWIR CQD based light emitters particularly with lead sulphide (PbS) CQDs due to their strong quantum confinement in that range. Most of these reported SWIR light emitters are in the wavelength range of 1000-1400 nm. PbS CQDs with excitonic peak above 1500 nm are much bigger and show different surface properties. Thus, developing efficient light emitters with these CQDs in the wavelength region above 1500 nm which has important bio, spectroscopy and communication-based applications, needs careful study of surface properties, effect of ligands, novel nanoscale active material structures, bandgap engineering. This proposal aims to synthesize stable, high-quality, mono-dispersed PbS CQDs in 1500-1700 nm region and use different methods like bandgap engineering in the active materials, core-shell interface engineering, finding suitable standard or newly developed 2D materials based high bandgap matrix to embed CQDs to improve the PLQY of the active materials. Once PLQY of the active materials is optimized, the CQDs will be utilized to form SWIR LED or down-converting films. The device performance will be optimized with device structure engineering and different layer optimization. Finally, optimized efficient SWIR light emitters in the range of 1500-1700 nm can be embedded in portable smart devices for prototype demonstration of short-range communications, IoT based portable spectrometer for healthcare monitoring, food quality checking, solvent detection etc. |