Color Enrichment Solids of Spectrally Pure Colloidal Quantum Wells for Wide Color Span in Displays

Abstract

On the other hand, display technologies employed first cathode ray tubes, then fluorescent lamps and more recently LEDs as backlight sources in liquid crystal displays (LCDs). Nowadays displays of organic LEDs [2,3] are also in use and quantum dot LEDs [4,5] and micro-LEDs [6,7] are currently in development. The driving force behind these changes has been partly improving the energy efficiency of the devices but also improving the colorimetric and photometric performance along with realizing a wide color gamut, [8] which can be realized when the spectrally narrow light sources are utilized. [9] When it comes to narrow-band light sources, the most obvious candidate is the lasers. [10,11] With their linewidths ≈1 nm, these devices offer extremely wide color gamuts and a significant spectral tuning while creating white light. Nevertheless, achieving high efficiencies covering the visible spectrum is currently a significant challenge for the widespread use of lasers in lighting applications. [12,13] The use of multiple LED chips of different colors also suffers from a similar problem. Realizing efficient LEDs in green and yellow colors to obtain white light is a big obstacle for their utilization in lighting. [14][15][16] Alternatively, colloidal quantum dots offer a solution to this problem as they possess finely tunable emission spectra. [9,[17][18][19] By employing strategically selected quantum dots emitting in specific colors, white Colloidal quantum wells (CQWs) are excellent candidates for lighting and display applications owing to their narrow emission linewidths (<30 nm). However, realizing their efficient and stable light-emitting solids remains a challenge. To address this problem, stable, efficient solids of CQWs incorporated into crystal matrices are shown. Green-emitting CdSe/CdS core/crown and red-emitting CdSe/CdS core/shell CQWs wrapped into these crystal solids are employed as proof-of-concept demonstrations of light-emitting diode (LED) integration targeting a wide color span in display backlighting. The quantum yield of the green-and red-emitting CQW-containing solids of sucrose reach ≈20% and ≈55%, respectively, while emission linewidths and peak wavelengths remain almost unaltered. Furthermore, sucrose matrix preserves ≈70% and ≈45% of the initial emission intensity of the green-and red-emitting CQWs after >60 h, respectively, which is ≈4× and ≈2× better than the drop-casted CQW films and reference (KCl) host. Color-converting LEDs of these green-and red-emitting CQWs in sucrose possess luminous efficiencies 122 and 189 lm W −1 elect , respectively. With the liquid crystal display filters, this becomes 39 and 86 lm W −1 elect , respectively, providing with a color gamut 25% broader than the National Television Standards Committee standard. These results prove that CQW solids enable efficient and stable color converters for display and lighting applications.