Fabrication of photoelectronic device
ITO-coated glass substrates were cleaned in an ultrasonic bath with detergent, deionized water, acetone, and isopropanol for 15 min and dried in the oven at 80 ◦C overnight.
After treatment with UV/ozone for 30 min, PEDOT:PSS (AI4083) was spin-coated onto the ITO-coated glass substrate at 4500 rpm for the 40s and dried for 10 min at 140 ◦C in air. Then the PVK was sipin-coated onto the PEDOT:PSS layer at 4000rpm for 40s followed by annealing at 130 ◦C in the glovebox.
The perovskite precursor solution was deposited on the substrate by spin-coating at speed of 5000 rpm for 15 s with instant chlorobenzene (CB) solvent cleaning during spinning. ,Then a scotch tape (3 M) was closely pasted on perovskite precursor film, then, the sample was annealing at 100 ◦C for 10 min.
Finally, TPBi (60 nm), LiF (1 nm) and Al (100 nm) were sequentially deposited by thermal evaporation under 5 × 10–7 Torr. The full structure of the device was : ITO/PEDOT:PSS/PVK/perovskite/TPBi/LiF/Al.
Figure. 1(a) Schematic diagrams for the encapsulation growth method of quasi-2D (PMA)2Csn-1PbnBr3n+1 perovskite films. GIWAXs patterns and corresponding schematic illustrations of quasi-2D (PMA)2Csn-1PbnBr3n+1 perovskite films fabricated by (b) conventional and (c) encapsulation growth method.
Characterization
The absorbance and XRD spectra of the perovskite films were measured using a Varian 5E UV/vis/NIR spectrophotometer and an X’Pert-MPD (Philips, Netherland), respectively. The film morphologies were obtained by AFM (BRUKER, Icon-PT-PLUS), SEM (S-2700, Hitachi, Japan). Steady-state PL spectra were measured using a F-7000 fluorescence spectrometer (Hitachi, Japan) by photoexciting the samples at 470 nm. Time-resolved PL measurements were recorded using a time-correlated single photon counting equipment (PicoQuant, Germany) with a 470 nm picosecond pulsed laser source (PicoQuant, LDH-P-C-470) and laser drivers (PicoQuant, PDL 800-D. The TEM images were performed on a Hitachi H-7500. The transient photo-conductivity of quasi-2D perovskite films was test according to previous study The confocal PL images were measured using an LSM 780 NLO laser scanning confocal microscope (Carl Zeiss) with a 100× oil immersion objective (a PlanAPO, NA = 1.46) with a 405 nm excitation diode laser. The EL spectra of the PeLEDs were measured using an SR-3AR spectrophotometer. The current J− V− L curves of the PeLEDs were measured using a Keithley 2450 source measure unit combined with a UVIS-50 spot photodetector. An impedance analyzer (1260 Impedance/Gain-Phase Analyzer, Solartron) was used to confirm the existence of the trap state of various samples. The EQE of the perovskite LED were recorded simultaneously by a commercialized system (XPQY-EQE, Guangzhou Xi Pu Optoelectronics Technology Co., Ltd.) that was equipped with an integrated sphere (GPS-4P-SL, Labsphere) and aphotodetector array (S7031–1006, Hamamatsu Photonics).