Rational molecular passivation for high-performance perovskite light-emitting diodes

Abstract

A major efficiency limit for solution-processed perovskite optoelectronic devices (e.g. light-emitting diodes, LEDs) is trap-mediated non-radiative losses. Defect passivation using organic molecules has been identified as an attractive approach to tackle this issue. However, implementation of this approach has been hindered by a lack of deep understanding of how the molecular structures affect the passivation effectiveness. We show that the so far largely ignored hydrogen bonds play a critical role. By weakening the hydrogen bonding between the passivating functional moieties and the organic cation featuring the perovskite, we significantly enhance the interaction with defects sites and minimize non-radiative recombination losses. Consequently, we achieve exceptionally high-performance near infrared perovskite LEDs (PeLEDs) with a record external quantum efficiency (EQE) of 21.6%. In addition, our passivated PeLEDs maintain a high EQE of 20.1% and a wall-plug efficiency of 11.0% at a high current density of 200 mA cm-2 , making them more attractive than the most efficient organic and quantum-dot LEDs at high excitations.

Sensitized Yb3+ Luminescence in CsPbCl3 Film for Highly Efficient Near‐Infrared Light‐Emitting Diodes

“…Lead halide perovskites exhibit significant potential for applications in LEDs because of their high color purity and a narrow full‐width at half‐maximum (FWHM) over the entire visible light spectrum, as well as their low‐cost solution processing without high‐temperature treatments . After halide perovskite LEDs was first reported in 2014 by Tan et al, EQEs of visible light emission have increased from below 1% to over 20%, which is comparable to those of the best organic LEDs in the visible wavelength region. Although tuning the optical bandgap of lead halide perovskites is achieved by substitution of A‐site cation (e.g., Cs + , CH 3 NH 3 + , and HC(NH 2 ) 2 + ), and halogen ion (Cl − , Br − , and I − ), pure lead‐based perovskite LEDs only emit below 800 nm.…”

Exploiting Two‐Step Processed Mixed 2D/3D Perovskites for Bright Green Light Emitting Diodes

“…In addition, passivation between the perovskite surface and the charge injection layers has been demonstrated to reduce the surface recombination significantly . Introducing this could be another route to bridge the performance gap between our current device stack and the state‐of‐the‐art devices showing EQE over 21% …”

Auger Effect Assisted Perovskite Electroluminescence Modulated by Interfacial Minority Carriers

“…However, their vulnerable lattice structures and ensuing accelerated degradation under high bias are responsible for the poor device lifetime 18,19. In this regard, near‐infrared perovskite LEDs (PeLED) showed decent operational stability probably owing to their low driven voltage,15,16,20 while green and blue ones severely suffer from short‐lived lifespans (turn‐on voltages typically higher than 3 V) 13,17. As expected, IAE assisted EL is a promising approach to mitigate device degradation for PeLEDs.…”