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.

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.…”

Enhanced Charge Transport via Metallic 1T Phase Transition Metal Dichalcogenides‐Mediated Hole Transport Layer Engineering for Perovskite Solar Cells

“…The morphology and crystallinity of perovskite film, sensitive to the nucleation and growth of perovskite crystals, is one of the key components which affects the device performance of PSCs. The formation of perovskite crystals can be directly influenced by surface properties of the underlying HTL layer in p‐i‐n structured PSCs . Figure S4 shows the contact angle measurements of perovskite solutions formed on PEDOT : PSS (7.0°) and P2‐WSe 2 (3.6°) films, indicating better wettability of perovskite solution on P2‐WSe 2 .…”

“…The formation of perovskite crystals can be directly influenced by surface properties of the underlying HTL layer in p-i-n structured PSCs. [35] Figure S4 shows the contact angle measurements of perovskite solutions formed on PEDOT : PSS (7.0°) and P2-WSe 2 (3.6°) films, indicating better wettability of perovskite solution on P2-WSe 2 . [36] When perovskite crystals are formed on foreign surface (PEDOT : PSS or P2-WSe 2 ), free energy required for the heterogeneous nucleation (DG heterogeneous ) becomes a dominant factor for the film formation, which depends on the contact angle (θ) as follow.…”

Effect of Acid Doping on Junction Characteristics of ITO/Polyaniline/N719/Ag Diode

“…polarons), which serve as hole transport materials in electronic devices. 14,15 A number of research papers have demonstrated the fabrication and junction characteristics of indium tin oxide (ITO)/PANI/metal diode systems. [16][17][18][19] ITO coated glass is usually used as an electron injection contact, while PANI is a low work function polymer that enables hole injection to the electrode.…”