Quantum dot-enhanced displays represent a significant advancement in display technology, leveraging the unique optical properties of semiconductor nanocrystals to achieve superior color performance, brightness, and energy efficiency. These displays utilize quantum dots (QDs) in various configurations, including on-chip color conversion, LCD backlighting, and electroluminescent panels, each offering distinct advantages in terms of color gamut, luminance, and operational lifetime. The development of cadmium-free alternatives such as indium phosphide (InP) and perovskite quantum dots further addresses environmental and regulatory concerns while maintaining high performance.

Quantum dots are nanoscale semiconductor particles with size-dependent optical properties due to quantum confinement effects. When excited by light or electrical current, they emit narrowband light with precise wavelength control, enabling highly saturated colors. This property makes them ideal for display applications where color accuracy and vibrancy are critical. The three primary implementations of QDs in displays—on-chip color conversion, LCD backlighting, and electroluminescent QD panels—each exploit these characteristics differently.

On-chip color conversion integrates quantum dots directly onto light-emitting diodes (LEDs) to convert blue or ultraviolet light into red and green emissions. This approach simplifies the display architecture by eliminating the need for color filters, improving light efficiency and color purity. The narrow emission spectra of QDs result in a wide color gamut, often exceeding 90% of the Rec. 2020 standard, which is a benchmark for high dynamic range (HDR) displays. The brightness of on-chip QD displays can reach upwards of 1000 nits, making them suitable for high-luminance applications. However, the proximity of QDs to the LED chip exposes them to high temperatures and intense light fluxes, which can degrade their performance over time. Advances in encapsulation techniques and robust QD materials have extended operational lifetimes to over 30,000 hours under typical usage conditions.

In LCD backlighting, quantum dots are used to enhance the performance of conventional liquid crystal displays. A blue LED backlight excites a layer of red and green QDs, often embedded in a film or dispersed in a glass matrix, to produce a white light spectrum with high color purity. This method, known as quantum dot enhancement film (QDEF), significantly improves the color gamut compared to traditional white LED backlights, achieving up to 95% of the DCI-P3 color space. The brightness of QD-enhanced LCDs can exceed 2000 nits, with energy efficiency gains of 20-30% due to reduced light absorption in the color filters. The lifetime of QDs in this configuration is less constrained by thermal effects than on-chip applications, often surpassing 50,000 hours. However, the reliance on liquid crystal shutters limits the contrast ratio and response times compared to self-emissive technologies.

Electroluminescent quantum dot displays (QLEDs) represent a more direct application of QDs, where the nanocrystals themselves are electrically excited to emit light. These panels operate similarly to organic light-emitting diodes (OLEDs) but with the potential for higher color purity and stability. Red, green, and blue QDs are patterned into subpixels and driven by thin-film transistors to create full-color images. The color gamut of electroluminescent QD displays can approach 100% of Rec. 2020, with brightness levels exceeding 2000 nits in prototype demonstrations. The lifetime of QLEDs is a critical focus area, with red and green QDs showing stability comparable to OLEDs, while blue QDs remain a challenge due to their higher energy excitations. Current research indicates lifetimes of 10,000 to 20,000 hours for blue QDs, which is a key barrier to commercialization.

Cadmium-based quantum dots, such as cadmium selenide (CdSe), have historically dominated the display market due to their excellent optical properties and ease of synthesis. However, regulatory restrictions on cadmium in consumer electronics have driven the development of alternative materials. Indium phosphide (InP) QDs have emerged as the leading cadmium-free option, offering comparable color purity and efficiency. InP-based QDs can achieve photoluminescent quantum yields exceeding 90% for red and green emissions, with lifetimes rivaling those of CdSe QDs. The blue emission from InP remains less efficient, prompting ongoing research into core-shell engineering and alloying strategies.

Perovskite quantum dots (PQDs) are another promising alternative, characterized by their tunable bandgaps and high defect tolerance. These materials exhibit photoluminescent quantum yields above 95% across the visible spectrum, with narrow emission linewidths similar to traditional QDs. However, perovskite QDs face challenges related to moisture and thermal stability, though recent advancements in surface passivation and encapsulation have improved their durability. Prototype displays using PQDs have demonstrated color gamuts exceeding 90% of Rec. 2020 and brightness levels over 1500 nits, with lifetimes now reaching 10,000 hours under ambient conditions.

The performance metrics of quantum dot-enhanced displays are often evaluated in terms of color gamut, brightness, and lifetime. The color gamut is typically measured as a percentage of a reference standard such as Rec. 2020 or DCI-P3, with higher values indicating more vibrant and accurate colors. Brightness, measured in nits, determines the display's visibility under various lighting conditions, while lifetime, measured in hours, reflects the operational durability before noticeable degradation occurs. For example, a QD-enhanced LCD might offer a color gamut of 95% DCI-P3, 2000 nits brightness, and 50,000 hours lifetime, whereas an electroluminescent QD panel might achieve 98% Rec. 2020, 2000 nits, and 20,000 hours for red and green subpixels.

The transition to cadmium-free quantum dots is a critical step in the commercialization of QD displays, aligning with global environmental regulations such as the European Union's Restriction of Hazardous Substances (RoHS) directive. InP and perovskite QDs are at the forefront of this shift, though each material presents unique technical hurdles. InP requires precise control over synthesis conditions to minimize defects, while perovskites demand robust encapsulation to prevent degradation. Despite these challenges, the progress in material science and device engineering continues to push the boundaries of what quantum dot-enhanced displays can achieve.

In summary, quantum dot-enhanced displays leverage the exceptional optical properties of semiconductor nanocrystals to deliver superior color performance, brightness, and efficiency across multiple implementations. The development of cadmium-free alternatives like InP and perovskite QDs ensures compliance with environmental standards while maintaining high display quality. As research advances, the lifetime and stability of these materials will further improve, solidifying their role in the future of display technology.