Fine‐Tuning Single‐Source White‐Light Emission from All‐Inorganic Corrugated 2D Antimony‐Halide Perovskite

Abstract

Corrugated 2D antimony‐halide perovskites such as Cs3Sb2Cl9 (CSC) are promising candidates for single‐source white‐light emission due to their ultra‐broadband spectra. However, CSC has a serious luminescence quenching phenomenon due to inadequate confinement of excitons. By the homovalent substitution of trivalent antimony cation Sb3+ by a small amount of trivalent rare earth (RE) cations RE3+, the photoluminescence intensities from high‐quality Cs3(Sb1−xREx)2Cl9 (CSRC) (RE = Ce, Sm, Nd, Y, Er, etc.) films at room temperature (RT) are over two orders of magnitude higher than that of CSC film. Especially, the photoluminescence quantum yield (PLQY) for the Cs3(Sb0.995Er0.005)2Cl9 film is 9.5% at RT, which is much higher than A3B2X9 perovskites previously reported for single‐source white‐light lighting. Furthermore, the Cs3(Sb0.995Er0.005)2Cl9 film exhibits an ultra‐broadband emission with the full width at half maximum reaching 554 meV at RT, resulting in a “warm” white‐light with the CIE coordinate (0.33, 0.46) and the correlated color temperature of 5450 K. The PLQY enhancement can be considered as the fact that a high activation energy by bandgap widening effect and Type‐I‐like “straddling” band alignment between Cs3Sb2Cl9 and Cs3Er2Cl9 lead to reducing nonradiative losses and increasing radiative recombination channels. Meanwhile, the spectral broadening can be considered to be attributed to strong effect of electron–phonon interaction.

Unraveling the Defect-Dominated Broadband Emission Mechanisms in (001)-Preferred Two-Dimensional Layered Antimony-Halide Perovskite Film

“…By fitting the PL spectra at 10 K, it is found that both of them consist of two Gaussian peaks positioned at 540 and 600 nm, respectively, as shown in Figure S3a,b. Similar to our previous work, the emission at 540 nm also exhibits a slight blueshift with increasing operating temperature (Figure S4), 40 which is consistent with the luminescence properties of the STE emission. 43 Another Gaussian peak at 600 nm is more pronounced at lower temperatures, following the characterization of the defect emission, 44 the mechanism of which will be revealed in the theoretical part below.…”

“…Cs 3 Sb 2 Cl 9 Films Fabrication: Materials, Cs 3 Sb 2 Cl 9 powders fabrication, and characterizations refer to our published work. 40 Here, we focus on the Cs 3 Sb 2 Cl 9 films fabrication and theoretical calculations method. Figure S1 shows the schematic representation of the improved solution-processing spin-coating method to prepare thin films of layered Cs 3 Sb 2 Cl 9 .…”

“…Generally, the quantum dots and nanocrystals feature narrowband emissions which are mainly attributed to free excitons (FEs), 22,27,29−33 whereas films and crystals whose emissions originated from STEs show broadband emissions (BEs). 20,26,40 Meanwhile, though the emissions are more or less accompanied by the defect transitions in all types of samples, 20,22,25,27,[29][30][31]33,34 it is not yet clear where the defect emission in A 3 B 2 X 9 originates. Among A 3 B 2 X 9 compounds, Cs 3 Sb 2 Cl 9 with a bandgap of 3.0 eV theoretically meets a criterion of single-source whitelight lighting (WLL).…”

“…41 Recently, our group has prepared Cs 3 Sb 2 Cl 9 thin film via the one-step powder-source evaporation method to assess its viability for WLL applications. 40 is worth noting that the films prepared through the evaporation method feature the X-ray diffraction (XRD) pattern of (110), 28,40 in contrast to (001)-preferred films prepared by solution processing. 18,20,24,39,42 Interestingly, defect emissions are generally observed in A 3 B 2 X 9 perovskites with the highest XRD peak of (003) as listed in Table S1, strongly indicating that the (001) surface has a distinctive defect property and plays an important role in photoluminescence (PL) properties.…”

“…The emissions can be very narrow or extremely broad depending on the types of samples and the mechanisms of emissions. Generally, the quantum dots and nanocrystals feature narrowband emissions which are mainly attributed to free excitons (FEs), ,,− whereas films and crystals whose emissions originated from STEs show broadband emissions (BEs). ,, Meanwhile, though the emissions are more or less accompanied by the defect transitions in all types of samples, ,,,,− ,, it is not yet clear where the defect emission in A 3 B 2 X 9 originates.…”