Fabrication of photoelectronic device
ITO-coated glass substrates were cleaned with Acetone and IPA for 15 min separately in sonication bath.
PEDOT:PSS was spin-coated at 3000rpm for 50s on the substrates after UVO3 treatment for 20 min. The PEDOT:PSS-casted substates were annealed at 145oC for 15 min in air and transferred to the glove box.
PVK in chlorobenzene was deposited at 3000rpm for 50s by spin-coating method, and annealed at 150oC for 15 min.
The perovskite precursor solution, including butylammonium bromide (BABr), lead bromide (PbBr2), and cesium bromide (CsBr), was deposited on the substrates at 4000rpm for 60s. In the middle of the spinning, chloroform was used as an antisolvent to drop on the substrates to activate the crystallization. Additional annealing process at 100oC was followed to evaporate the residual solvents.
Eventually, TPBi and LiF/Al were deposited by thermal evaporation method.
Figure. 1(a) Perovskite films on substrates under UV lamp. (b) Electroluminescence of quasi-2D PeLEDs operating under voltage. (c) Schematic of antisolvent drop method for perovskite film deposition using perovskite precursor solution. (d) Absorbance spectra of quasi-2D perovskite films depending on the ratio of BABr.
Characterization
The absorbance and XRD spectra of the perovskite films were measured using Cary 5000 UV-Vis-NIR spectrophotometer and an XRD (Miniflex 600) using a diffracted beam monochromator set for Cu-Kα radiation (λ = 1.54056 Å). The 2θ scan range was 10o–60o with a step size of 0.01o, respectively. The TRPL of the samples were measured using a HORIBA spectrophotofluorometer with TCSPC with pulsed nano LED 316 nm (±10 nm). The absolute PLQY of the samples were measured using a HORIBA FluoroMax Plus spectrofluorometer paired with K-sphere petite internal, directly coupled with Integrating Sphere. The current J− V curves of the PeLEDs were measured using a Keithley 2450 source measure unit. The EQE and EL spectra of the perovskite LED were recorded simultaneously by a commercialized system (CS-2000 Spectroradiometer, Konica Minolta).