Modulation of Electronic States of Hybrid Lead Halide Perovskite Embedded in Organic Matrix

Abstract

The modulation of electronic states of MAPbX3 perovskite nanocrystals (PNCs) (MA = CH3NH3+ and X = Br− and I−) is presented as a function of crystallite size in organic semiconductor matrix forming a type‐I heterostructure with bulk perovskites. Organic semiconductor molecule (4,4′‐bis[9‐dicarbazolyl]‐2,2′‐biphenyl [CBP] and bathocuproine [BCP]) precursors are mixed in different volumetric ratios with MAPbX3 perovskite precursors to prepare thin films. This results into an easy growth of MAPbX3 PNCs of tunable sizes from ≈110 to ≈10 nm in organic semiconductor matrix. A blue shift is observed in the photoluminescence peak (PLmax) energy over a range of ≈200 meV for MAPbI3 PNCs embedded in the BCP matrix. However, PLmax energy tunes over ≈32 meV only with a similar volumetric concentration in the case of MAPbBr3 PNCs in the same BCP matrix. Moreover, the PL blue shift is even lower in the case of CBP matrix in comparison with BCP matrix for both the perovskites. This discrepancy could be resolved by determining the resultant crystallite size using X‐ray diffraction studies and the Debye–Scherrer formula. Results about blue shift in the PL peak can be explained using the classic particle‐in‐a‐box versus excitonic Bohr radius model under a weak confinement regime.

Optimization of Composition with Reduced Phase Impurity in Quasi‐2D Perovskite for Electroluminescence

“…[ 35–37 ] We have also fitted a 3D peak close to 14.89° for all the n compositions using Gauss multipeak fitting functions (Figure S1 and Table S2, Supporting Information). This allowed us to determine the average crystallite size [ 38,39 ] using the Debye–Scherrer formula corresponding to the 3D phase in these compositions, where the crystallite size varied from 160 nm ( n = ∞) to ≈70 nm ( n = 4 and 5) and to ≈40 nm ( n = 2 and 3).…”

Origin of Contrasting Emission Spectrum of Bromide versus Iodide Layered Perovskite Semiconductors

“…First-order diffraction peaks are fitted with a Gaussian curve to determine the average crystallite size in thin films of 2D perovskites, Figure S1b. Debye–Scherrer formula ( D avg = k λ/(β cos θ), where k is the shape factor, λ is the X-ray wavelength, β is the full width at half-maximum (fwhm) of the XRD peak, and θ is the Bragg angle) is used to determine the average crystallite size . The average crystallite size for (PEA) 2 PbBr 4 and (PEA) 2 PbI 4 is 65 and 164 nm, respectively.…”