Fine Control of Perovskite Crystallization and Reducing Luminescence Quenching Using Self‐Doped Polyaniline Hole Injection Layer for Efficient Perovskite Light‐Emitting Diodes

Abstract

Organic–inorganic hybrid perovskites (OHPs) are promising emitters for light‐emitting diodes (LEDs) due to the high color purity, low cost, and simple synthesis. However, the electroluminescent efficiency of polycrystalline OHP LEDs (PeLEDs) is often limited by poor surface morphology, small exciton binding energy, and long exciton diffusion length of large‐grain OHP films caused by uncontrolled crystallization. Here, crystallization of methylammonium lead bromide (MAPbBr3) is finely controlled by using a polar solvent‐soluble self‐doped conducting polymer, poly(styrenesulfonate)‐grafted polyaniline (PSS‐g‐PANI), as a hole injection layer (HIL) to induce granular structure, which makes charge carriers spatially confined more effectively than columnar structure induced by the conventional poly(3,4‐ethylenedioythiphene):polystyrenesulfonate (PEDOT:PSS). Moreover, lower acidity of PSS‐g‐PANI than PEDOT:PSS reduces indium tin oxide (ITO) etching, which releases metallic In species that cause exciton quenching. Finally, doubled device efficiency of 14.3 cd A‐1 is achieved for PSS‐g‐PANI‐based polycrystalline MAPbBr3 PeLEDs compared to that for PEDOT:PSS‐based PeLEDs (7.07 cd A‐1). Furthermore, PSS‐g‐PANI demonstrates high efficiency of 37.6 cd A‐1 in formamidinium lead bromide nanoparticle LEDs. The results provide an avenue to both control the crystallization kinetics and reduce the migration of In released from ITO by forming OIP films favorable for more radiative luminescence using the polar solvent‐soluble and low‐acidity polymeric HIL.

Chemically Robust Indium Tin Oxide/Graphene Anode for Efficient Perovskite Light-Emitting Diodes

“…Both PL decay curves were fitted using a biexponential decay model. 2,5,6 A fit to the decay model indicated that MAPbBr 3 on ITO/BufHIL had PL lifetime τ ∼22.1 ns, which matches well with the previous results. 5 After graphene insertion, PL lifetime was increased by a factor of ∼4 (τ ∼87.9 ns).…”

Feasible Modification of PEDOT:PSS by Poly(4-styrenesulfonic acid): A Universal Method to Double the Efficiencies for Solution-Processed Organic Light-Emitting Devices

“…After dipping the ITO substrate into the PEDOT:PSS 4083 solution and m -PEDOT:PSS (50 wt % PSSA) solution for 2 h, the In 3d and Sn 3d characteristic peaks of the ITO electrode were decreased compared with the reference. Nevertheless, the diffusion of In and Sn under the EL process can be inhibited by some other approach based on the previous work . This ITO etching experiment is not exactly the same situation as that of the real device.…”

Manipulating the Phase Distributions and Carrier Transfers in Hybrid Quasi‐Two‐Dimensional Perovskite Films

“…According to previous study, when the solvent evaporates slowly, the crystal growth becomes slow and a larger grain size of perovskite can be formed. Here, both methods (adding MACl and DMSO) slow the crystal growth and gives rise to larger and more uniform perovskite crystals.…”