Fig. 1. Optical properties of CIZS NCs and TPE-4Cl. (a) Absorption (Abs, gray lines) and PL spectra of CIZS film (bottom one, yellow line) and TPE-4Cl film (top one, blue line). The red dotted lines are the PL excitation (PLE) spectra of CIZS and the TPE-4Cl film; the inset shows the molecular structure of TPE-4Cl and the diagram of the CIZS NCs. (b) Photographs of TPE-4Cl and CIZS NCs in a toluene solution and films under UV light (365 nm). (c) PL spectra and corresponding fitted curves of the mixed film sample of TPE-4Cl and CIZS NCs. (d) and (e) Time-resolved PL curve and the corresponding fitted curves of TPE-4Cl and mixed film (monitored at 455 nm) as well as CIZS NCs and mixed film (monitored at 568 nm).

Fig. 2. Color regulation and luminescence mechanism of single-TFB HTL device WLEDs. (a) Normalized EL spectra of single-TFB HTL devices based on TPE-4Cl:CIZS NCs EMLs with different ratios at 5 V. (b) EL spectra of the hybrid film (10:1), TFB film, and CIZS NCs, respectively. (c) Schematic of the EL mechanism hypothesis.

Fig. 3. Schematic and cross-sectional characterization of the devices. (a) Schematic of the device structure. (b) The cross-sectional SEM image and (c) the band alignment diagram of as-fabricated devices.

Fig. 4. Device performance of double-layered TFB/TPD HTLs. (a) Schematic of the carrier injection process. (b) EL spectra of the hybrid film (5:1), TPE-4Cl film, and CIZS NCs, respectively. The inset is the image of an LED under the driving voltage of 5 V. (c) Current density-voltage-luminance (J−V−L) curve of the device. (d) EQE and PE as a function of luminance. (e) The evolution of EL spectra with varying voltage. (f) The corresponding 1931 CIE coordinate of the EL spectra shown.

Fig. 5. Device performance of regulation of double-HTLs: (a) EL spectra and (b) L−J−V curves with different concentrations of TFB. (c) EL spectra and (d) L−J−V curves with different concentrations of TPD.