Ultrafast Thermodynamic Control for Stable and Efficient Mixed Halide Perovskite Nanocrystals

Abstract

Low photoluminescence quantum yield (PLQY) and spectra instability, the two most difficult challenges in blue-emitting CsPbBr x Cl 3−x NCs, have not yet been solved. Quickly controlling the reaction thermodynamics is crucial to enhance crystallinity, thus PLQY and spectra stability, but it has been ignored until now. An ultrafast thermodynamic control (UTC) strategy is designed by utilizing liquid nitrogen to instantaneously freeze the superior crystal lattices of CsPbBr x Cl 3−x NCs formed at high temperature. The average cooling rate exhibits a 33-fold increase compared to conventional ice-water cooling (from 1.5 to 50 K s −1 ). This UTC can make the reaction thermodynamic energy of the system lower than the threshold very quickly. Therefore, abrupt termination of further crystal growth can be achieved, which also avoids additional nucleation at low temperature. With the assist of defect passivation, the final blue-emitting CsPbBr x Cl 3−x NCs exhibit an absolute PLQY of 98%, representing the highest value in Pb-based blue perovskites to date. More importantly, they exhibit superior spectra instability. This UTC strategy not only represents a new avenue to synthesize perovskite NCs with excellent crystal quality and ultrahigh PLQY, but also provides a good reference to deal with the recognized bottleneck of spectra instability.

Self‐Induced Type‐I Band Alignment at Surface Grain Boundaries for Highly Efficient and Stable Perovskite Solar Cells

“…In addition, IPSG optimization did not change the bandgap of the perovskite films (Figure S13, Supporting Information), but effectively decreased the Urbach energy (Figure S14, Supporting Information), beneficially reducing the degree of crystal disorder at the interface. [17,49] Surface manipulation is an efficient strategy to reduce the carrier loss and improve the photoelectric properties of perovskite film, [6,11] since the defect density on the surface of perovskite films is more than two orders of magnitude higher than that in the interior. [44] Space-charge-limited current (SCLC) technique (indium tin oxide (ITO)/perovskite/Au) was conducted (see Figure 3a,b and Note S3, Supporting Information) to further quantify the defect density of perovskite film.…”

Improved Photostability in Fluorinated 2D Perovskite Single Crystals

“…Although there are many published papers on light- and oxygen/moisture-induced degradation of 3D perovskites [ 13 , 14 , 15 , 16 , 17 ] very few studies have been carried out on the stability of 2D perovskites [ 18 , 19 , 20 ]. In a recent work [ 18 ], the behaviour of 2D phenethylammonium lead iodide perovskite (PEAI) single crystals under light irradiation was examined.…”

Ultrasensitive Temperature Sensing Based on Ligand‐Free Alloyed CsPbClxBr3−x Perovskite Nanocrystals Confined in Hollow Mesoporous Silica with High Density of Halide Vacancies

“…The phase segregation induced spectrum instability has been frequently reported in alloyed CsPbCl x Br 3− x NCs, [ 59,60 ] which should be addressed before the sensing applications. As shown in Figure a; Figure S9, Supporting Information, the PL of CsPbCl 1.2 Br 1.8 NCs@ h ‐SiO 2 @EVA film retains at 99.7% of the initial intensity after the heating/cooling cyclings from 25 °C to 60 °C, showing the high thermal stability of CsPbCl 1.2 Br 1.8 NCs@ h ‐SiO 2 @EVA film.…”