Provided are systems, compositions and methods that useful in any setting where generating and tracking light is used. The systems, methods and compositions contain as a component flexible, transparent membrane-based materials that include light emitting diodes (LEDs). The LEDs can include or be formed from colloidal quantum dots (CQDs) as an active layer. The CQDs can be formed from solution-processed semiconductor nanocrystals. They have a tunable band gap energy that can be readily tuned by adjusting the size of the nanocrystals. Transparent membrane-based LED arrays exhibit emission wavelength that can be tuned anywhere in the range of 800-2000 nm. The LEDs are highly transparent in the visible wavelength range with the exception of the CQD active layer. The CQD-based LEDs are components of any device or system wherein generating and/or tracking reflected light is utilized, such as in tracing the location and movement of a living individual, or an inanimate object. Also provided are garments used in movement tracking, and imaging devices, which include cameras and microscopes, and systems for volume capture, body motion tracking, eye tracking systems and devices, motion capture systems, simulcam technologies, computer generated characters, holograms, eye wear, such as glasses, goggles, and virtual reality headsets, and medical devices that involve imaging, such as devices that involve imaging of the eye for diagnosing and/or treating eye disorders.

A semiconductor device includes an anode, a cathode, a first functional layer between the anode and cathode, and a second functional layer between the first functional layer and the cathode. The first functional layer contains a first quantum dot having a first ligand, and the second functional layer contains a second quantum dot having a second ligand different from the first ligand. The second ligand is an aromatic compound having a sulfide bond and an ester bond.

A substituted nanocrystal including a nanocrystal represented by Formula 1, wherein a portion of halogen atoms in an outermost region of the nanocrystal is substituted with a chloride anion, a polyatomic anion, or a combination thereof:
AMX.sub.3Formula 1 wherein, in Formula 1, A is cesium, rubidium, or an ammonium salt; M is germanium, tin, or lead; and X is iodine or bromine.

Provided are systems, compositions and methods that useful in any setting where generating and tracking light is used. The systems, methods and compositions contain as a component flexible, transparent membrane-based materials that include light emitting diodes (LEDs). The LEDs can include or be formed from colloidal quantum dots (CQDs) as an active layer. The CQDs can be formed from solution-processed semiconductor nanocrystals. They have a tunable band gap energy that can be readily tuned by adjusting the size of the nanocrystals. Transparent membrane-based LED arrays exhibit emission wavelength that can be tuned anywhere in the range of 800-2000 nm. The LEDs are highly transparent in the visible wavelength range with the exception of the CQD active layer. The CQD-based LEDs are components of any device or system wherein generating and/or tracking reflected light is utilized, such as in tracing the location and movement of a living individual, or an inanimate object. Also provided are garments used in movement tracking, and imaging devices, which include cameras and microscopes, and systems for volume capture, body motion tracking, eye tracking systems and devices, motion capture systems, simulcam technologies, computer generated characters, holograms, eye wear, such as glasses, goggles, and virtual reality headsets, and medical devices that involve imaging, such as devices that involve imaging of the eye for diagnosing and/or treating eye disorders.

A substituted nanocrystal including a nanocrystal represented by Formula 1, wherein a portion of halogen atoms in an outermost region of the nanocrystal is substituted with a chloride anion, a polyatomic anion, or a combination thereof:

AMX.sub.3Formula 1 wherein, in Formula 1, A is cesium, rubidium, or an ammonium salt; M is germanium, tin, or lead; and X is iodine or bromine.

A semiconductor device includes an anode, a cathode, a first functional layer between the anode and cathode, and a second functional layer between the first functional layer and the cathode. The first functional layer contains a first quantum dot having a first ligand, and the second functional layer contains a second quantum dot having a second ligand different from the first ligand. The second ligand is an aromatic compound having a sulfide bond and an ester bond.