Fig. 1. Top-view SEM images of (a) rapidly crystallized and (b) conventional hot-cast 2D perovskite films. XRD patterns of 2D-RPP films fabricated with (c) rapid crystallization and (d) conventional hot-casting methods on glass/ITO/PEDOT:PSS (the scale of the $y$ axis was adjusted identically for both XRD spectra).

Fig. 2. Steady-state PL spectra of 2D-RPP films fabricated by (a) rapid crystallization and (b) conventional hot-casting approaches on glass/ITO. TA mapping of (c) rapidly crystallized and (d) conventional hot-cast 2D-RPP films with respect to time delays. TA spectra at different time delays of the (e) rapidly crystallized and (f) conventional hot-cast 2D-RPP films.

Fig. 3. TA kinetics of the (a) rapidly crystallized and (b) conventional hot-cast 2D perovskite films probed at different wavelengths as a function of decay time. Current–voltage curves of hole-only devices fabricated from (c) rapidly crystallized and (d) conventional hot-cast 2D-RPP films obtained under dark conditions using the SCLC method. Hole-only devices in a configuration of glass/ITO/PEDOT:PSS/2D-RPPs/PTAA/Al were utilized.

Fig. 4. (a) Device configuration schematic and (b) band energy alignment of the PeLEDs. EL properties of PeLEDs fabricated from rapidly crystallized 2D perovskite films. (c) EL spectrum under a bias voltage of 6 V. (d) $J-V$ and (e) $L-V$ characteristics.

Fig. 5. Stability of PeLEDs prepared from rapidly crystallized 2D perovskite films. (a) EL spectra as a function of bias voltage from 5 to 7 V. (b) EL spectra as a function of operation time. The intensities of the EL spectra negligibly changed under continuous operation for 5 min. (c) CIE 1931 chromatic coordinates and (d) digital photograph of the operating device.

Table 1. Performance parameters of the PeLED prepared from rapidly crystallized 2D-RPP films.