Room‐Temperature Ion‐Exchange‐Mediated Self‐Assembly toward Formamidinium Perovskite Nanoplates with Finely Tunable, Ultrapure Green Emissions for Achieving Rec. 2020 Displays

Abstract

Delicate engineering of chromaticity is required to faithfully reproduce colors in a backlit display, this is extremely difficult for green downconverters because the human eye is highly sensitive to green colors. The central challenge is to achieve finely tunable green emissions in the narrow range of 525-535 nm while keeping the full width at half maximum (FWHM) <25 nm at the same time. Here, a room-temperature ion-exchange-mediated self-assembly strategy for preparing FAPbBr 3 (FA = CH(NH 2 ) 2 + ) nanoplates (NPs) to fulfill this goal is introduced. 2D layered OA 2 PbBr 4 (OA is octadecylamine) NPs are first synthesized by spontaneous reprecipitation, and are then transformed into FAPbBr 3 NPs through a OA + -to-FA + exchange induced self-assembly of HP monolayers. A c-axis contraction in this process makes a relative large thickness variation in OA 2 PbBr 4 NPs, which can be realized by simply varying the precursor concentration, only result in a small thickness change in subsequent FAPbBr 3 NPs, thereby enabling finely tunable emissions in the range of 525-535 nm along with FWHM <25 nm and a quantum yield up to 85%. As a downconverter, the FAPbBr 3 NPs realize an ultrapure green backlight that covers ≈95% Rec. 2020 standard in the CIE 1931 color space.

Vapor‐Phase Growth of CsPbBr3 Microstructures for Highly Efficient Pure Green Light Emission

“…Within the experimental errors, the PLQYs of microspheres can be as high as 75% for all microspheres and shows no apparent size dependence. This is the highest PLQYs for perovskite‐based pure green emitters up to date (Table S1, Supporting Information) . In addition, PL mapping image indicates that the emission is rather uniform for the entire microsphere even at the area close to the edge (Figure S5, Supporting Information).…”

“…While the red emitters have been well developed, there is only weakly emitting in blue and no true green emission (525–535 nm) has been achieved, which is critical to replicate high quality white light display since human eyes are extremely sensitive to green light . CsPbBr 3 is a potential candidate to close the so‐called “green gap” due to its suitable band gap and ultrahigh PLQY . Nevertheless, CsPbBr 3 bulk thin films are able to only emit a blue‐green color light (≈520 nm) while CsPbBr 3 quantum dots exhibit a blueshifted emission wavelength due to quantum confinement effect, both of which cannot truly replicate the green emission .…”

“…Nevertheless, CsPbBr 3 bulk thin films are able to only emit a blue‐green color light (≈520 nm) while CsPbBr 3 quantum dots exhibit a blueshifted emission wavelength due to quantum confinement effect, both of which cannot truly replicate the green emission . Yu et al have successfully demonstrated ultrapure green emission with high PLQY in formamidinium perovskite nanoplates at the sacrifice of the long‐term stability due to the presence of the organic cations . Recently, spontaneously self‐assembled CsPbBr 3 supercrystals have been achieved with emission wavelength around 530 nm, which is believed to be able to fill the green gap .…”

Advances in inorganic and hybrid perovskites for miniaturized lasers

“…Specifically, such advantages as low cost, large optical gain, high PLQY, long carrier lifetime, low trap state density, large exciton binding energy, tunable wavelength covering ultraviolet to the near-infrared regime and so on, all support the use of metal halide perovskites as a new class of strong emitters for a wide array of applications, such as laser display, optical interconnection, 3D sensing and imaging, etc. [16,28,102,115,116]. The excellent properties and flexible structures of perovskites also ensure their strong compatibility for integration.…”

Hybrid light emitting diodes based on stable, high brightness all-inorganic CsPbI3 perovskite nanocrystals and InGaN

“…They have a band gap energy tunable in a wide spectral range, narrow emission lines and high photoluminescence (PL) quantum yield (QY). [1][2][3] These nanomaterials have potential applications in optoelectronics, [4][5][6][7][8][9][10][11][12][13] including lasers, 5 solar cells, 6,7 screen displays, 8 light-emitting diodes (LEDs) [9][10][11]14,15 and photodetectors. 12,16 However, despite recent important advances in their synthesis and exploitation, 10,12,13,16,17 the long-term instability and degradation of the QY over time should be addressed to enable the emergence of a robust class of materials for fundamental and applied research.…”