Enhancing violet photoluminescence of 2D perovskite thin films via swift cation doping and grain size reduction

Abstract

Perovskite materials are emerging as suitable materials for low-cost, high efficiency optoelectronics. In this study, we reported the surface modification of 2D (PEA)2PbBr4 for violet emission using PEG doping followed by a newly developed step called swift cation doping (SCD) where phenylethylammonium cations (PEA+) in isopropanol (IPA) are abruptly applied during crystallization. 2D Perovskite doped with PEG using SCD resulted in smaller grain, smoother surface, higher film density, higher photoluminescence quantum efficiency, and longer average PL lifetime. These features are highly beneficial for photoluminescence application and can be easily applied to enhance other perovskite LED thin films.

Enhancing High Humidity Stability of Quasi‐2D Perovskite Thin Films through Mixed Cation Doping and Solvent Engineering

“…Low E t values in MCD sample corresponds less electronic defects at the surface like dangling bonds or dislocation . We attribute this improvement to better surface passivation and more complete crystallization at the surface due the nature of repeated cation treatment . The significance of deep defect states can be further discussed by the ratio of the PV amplitudes measured at 1.1 and 1.7 eV (R 1.1eV /R 1.7eV ) as shown in Figure A (b).…”

“…[63,65,66] We attribute this improvement to better surface passivation and more complete crystallization at the surface due the nature of repeated cation treatment. [43,45] The significance of deep defect states can be further discussed by the ratio of the PV amplitudes measured at 1.1 and 1.7 eV (R 1.1eV /R 1.7eV ) as shown in Figure 5A (b). R 1.1eV /R 1.7eV was higher for reduced dimensional perovskite (n40).…”

“…Excess cation promotes homogenous nucleation from supersaturation. [44,45] Herein, we demonstrated stable intermixed MA/FA-based quasi-2D perovskite films through facile, newly-developed sequential treatment called mixed cation doping (MCD) where mixed MA and FA cations in isopropanol (IPA) are gradually applied during film deposition. We achieved high crystallinity quasi cubic structural of (PEA) 2 (MA) n-1-x FA x Pb n X 3n + 1 , evolved from β-MAPbI 3 (tetragonal structure) [46] and α-FAPbI 3 (trigonal structure).…”

Modifying morphology and defects of low-dimensional, semi-transparent perovskite thin films via solvent type

“…Compact TiO 2 layer was then deposited by spin-coating as described in our previous publications. 13,24 Lead halide mixtures of (PEA) 2 (MA) nÀ1 Pb n I n+1 Br 2n (n ¼ 1, 3, and 5) were prepared and studied in various solvent types and ratios. The perovskite precursors that were prepared according to Table 1 were separately dissolved in DMF, DMSO, GBL : DMSO ¼ 7 : 3, and DMF : DMSO ¼ 8 : 2.…”

“…Low dimensional perovskites, (R) 2 (MA) nÀ1 Pb n I 3n+1 , commonly referred to as 2D (low n values) and quasi-2D or 2D/ 3D (large n values), have been shown to exhibit high environmental resistance due to the intercalation of a large organic cation (R) like phenethylammonium (PEA) between the perovskite layers. [13][14][15][16] The dimensionality of perovskite also offers another path for tuning the electronic band gap where lower dimension (low n values) results in a larger band gap and hence lighter color. The decrease in the effective charge carrier mobility, which could be characterized by the optical pump-THz probe (OPTP) spectroscopy, was obtained with the decrease in the dimensionality, i.e., higher PEA content.…”