Cellulose‐Assisted Formation of 2D Hybrid Halide Perovskite Nanocrystals with Enhanced Stability for Light‐Emitting Devices

Abstract

A common approach to enhance the stability of metal halide perovskites (MHPs) implemented in optical and optoelectronic devices is to incorporate polymer additives into the perovskite layer. A β‐(1,4) cellulose oligosaccharide (COS) synthesized by mechanocatalytic depolymerization of cellulose has been incorporated to films of the BA2MA4Pb5I16 (BA = n‐butylammonium and MA = methylammonium) two‐dimensional (2D) Ruddlesden‐Popper (RP) hybrid perovskite. Scanning Electron Microscopy (SEM) images displayed a three‐fold reduction of the 2D RP perovskite grains (≈30–40 nm), close to the quantum confinement scale. The analysis of the dark J–V curves of single carrier devices by using the space charge limited current (SCLC) method resulted in a rise of the defect concentration. A notable 14‐fold increase in the photoluminescence (PL) signal at high COS content is detected. Moreover, the analysis of the temperature dependence PL measurements (80–300 K) resulted in a larger exciton binding energy, Eb = 180 to 370 meV, at high COS content. Light emitting diodes of the 2D RP perovskites (PeLEDs) are fabricated w/o the COS compound. The stability test performed under operation (5 V) displays 20 times higher operational lifetimes at high COS content while the luminance is also increased in the devices with the COS compound.

Dielectric Engineering of 2D Organic–Inorganic Hybrid Perovskites

“…15 The gradual increase in dielectric constant is in line with the decrease in excitonic binding energy for CsPbX 3 by changing the halides (64, 33, and 15 meV for CsPbCl 3 , CsPbBr 3 , and CsPbI 3 , respectively). 16 Such a composition-dependent trend is also in agreement with nanocrystalline CsPbX 3 (75,40, and 20 meV for CsPbCl 3 (5 nm), CsPbBr 3 (7 nm), and CsPbI 3 (12 nm)), as reported by Kovalenko and co-workers. 17 Except for halide substitution, the replacement of Cs + by the organic cation CH 3 NH 3 + leads to the formation of CH 3 NH 3 PbX 3 (X = Cl, Br, I) with an increase of the dielectric constant (e.g., 5.5 for CH 3 NH 3 PbI 3 ).…”