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Elucidating and mitigating degradation processes in perovskite light‐emitting diodes

DOI: 10.1002/aenm.202002676 DOI Help

Authors: Zahra Andaji-garmaroudi (University of Cambridge) , Mojtaba Abdi-jalebi (University of Cambridge; University College London) , Felix U. Kosasih (University of Cambridge) , Tiarnan Doherty (University of Cambridge) , Stuart Macpherson (University of Cambridge) , Alan R. Bowman (University of Cambridge) , Gabriel J. Man (Uppsala University) , Ute B. Cappel (KTH ‐ Royal Institute of Technology) , Hakan Rensmo (Uppsala University) , Caterina Ducati (University of Cambridge) , Richard H. Friend (University of Cambridge) , Samuel D. Stranks (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Energy Materials , VOL 11

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 22668

Abstract: Halide perovskites have attracted substantial interest for their potential as disruptive display and lighting technologies. However, perovskite light‐emitting diodes (PeLEDs) are still hindered by poor operational stability. A fundamental understanding of the degradation processes is lacking but will be key to mitigating these pathways. Here, a combination of in operando and ex situ measurements to monitor the performance degradation of (Cs0.06FA0.79MA0.15)Pb(I0.85Br0.15)3 PeLEDs over time is used. Through device, nanoscale cross‐sectional chemical mapping, and optical spectroscopy measurements, it is revealed that the degraded performance arises from an irreversible accumulation of bromide content at one interface, which leads to barriers to injection of charge carriers and thus increased nonradiative recombination. This ionic segregation is impeded by passivating the perovskite films with potassium halides, which immobilizes the excess halide species. The passivated PeLEDs show enhanced external quantum efficiency (EQE) from 0.5% to 4.5% and, importantly, show significantly enhanced stability, with minimal performance roll‐off even at high current densities (>200 mA cm−2). The decay half‐life for the devices under continuous operation at peak EQE increases from <1 to ≈15 h through passivation, and ≈200 h under pulsed operation. The results provide generalized insight into degradation pathways in PeLEDs and highlight routes to overcome these challenges.

Journal Keywords: degradation; halide perovskites; ion migration; light‐emitting diodes; passivation

Subject Areas: Materials, Energy

Instruments: I09-Surface and Interface Structural Analysis