Luminescent Nanomaterials for Energy-Efficient Display and Healthcare

Luminescent quantum dots (QDs) and perovskite nanocrystals (PNCs) are promising, efficient energy converters for advanced displays and light sources. Their widespread applications in the photoluminescence (PL)-based displays have been achieved through color enhancement films and patterned color-converters. Meanwhile, electroluminescence (EL) devices based on QDs and PNCs are still under active development, but emerging applications in the healthcare domains could accelerate their adoption. Herein, we first analyze the QD color-conversion displays guided by state-of-the-art research and then summarize the evolution of in situ strategies to fabricate efficient and stable PNC−polymer composites. Subsequently, we introduce the application of flexible QD light-emitting devices for healthcare as a potential early target market. Remaining challenges and future perspectives of QDs and PNCs as light-converters for PL displays, and of QDs for EL applications in healthcare, are analyzed. The past decade has seen the establishment of colloidal quantum dots (QDs) as a key element of advanced display technologies and the upsurge of perovskite nanocrystals (PNCs) as strong contenders to share the stage with QDs. QDs and PNCs both have several desirable properties for photonic and optoelectronic applications, with PNCs attracting an increased interest in the past few years. These PNCs generally have the formula ABX3, where A is a monovalent cation (Cs, CH3NH3 + (MA), or CH(NH2)2 + (FA)), X a halide anion (Cl−, Br−, or I−), and B a metal cation, typically Pb, with its substitution in the PNC structure being a research topic of current relevance due to lead toxicity concerns. Putting them in perspective, both luminescent nanomaterials are considered to have the capability of helping next-generation display technologies to achieve a wide color gamut (WCG) and high energy efficiency simultaneously. These luminescent semiconductor nanomaterials can function in two different energy conversion modes, depending on the excitation mechanism. In the photoluminescence (PL) mode, the emission results after photoexcitation using an external light source with photon energy higher than or equal to the optical bandgap energy (hν ≥ Eg) of the direct bandgap semiconductor. Meanwhile, in the electroluminescence (EL) mode, the emission originates after electro-excitation by application of an external electric field. Two main PL applications of the luminescent nanomaterials have been considered for displays to date. The first-generation application of QDs in displays is the use of a color enhancement film (CEF), for which the luminescent nanomaterials are embedded in or coated on a film. Today, the quantum dot enhancement film (QDEF) technology has been widely used for WCG liquid crystal displays (LCDs), achieving over 90% Rec.2020 coverage. The Rec.2020 (also known as BT.2020) is one of the three main color gamut standards, covering the largest area of the visible color space, and has been designed for high-dynamic-range displays. Recently, the Received: December 16, 2021 Accepted: February 3, 2022 Quantum dots and perovskite nanocrystals both have tunable emission wavelength, high photoluminescence quantum yield (PLQY), and high color purity, with perovskite nanocrystals attracting increased interest in the past few years due to their narrower emission full width at half-maximum, larger absorption coefficient, easier processing, and lower cost. Pespec iv e http://pubs.acs. org/journal/aelccp © XXXX The Authors. Published by American Chemical Society 1001 https://doi.org/10.1021/acsenergylett.1c02745 ACS Energy Lett. 2022, 7, 1001−1020 D ow nl oa de d vi a U N IV O F C E N T R A L F L O R ID A o n Fe br ua ry 1 7, 2 02 2 at 1 6: 51 :0 4 (U T C ). Se e ht tp s: //p ub s. ac s. or g/ sh ar in gg ui de lin es f or o pt io ns o n ho w to le gi tim at el y sh ar e pu bl is he d ar tic le s.