Phenylalkylammonium passivation enables perovskite light emitting diodes with record high-radiance operational lifetime: the chain length matters

Abstract

Perovskite light emitting diodes suffer from poor operational stability, exhibiting a rapid decay of external quantum efficiency within minutes to hours after turn-on. To address this issue, we explore surface treatment of perovskite films with phenylalkylammonium iodide molecules of varying alkyl chain lengths. Combining experimental characterization and theoretical modelling, we show that these molecules stabilize the perovskite through suppression of iodide ion migration. The stabilization effect is enhanced with increasing chain length due to the stronger binding of the molecules with the perovskite surface, as well as the increased steric hindrance to reconfiguration for accommodating ion migration. The passivation also reduces the surface defects, resulting in a high radiance and delayed roll-off of external quantum efficiency. Using the optimized passivation molecule, phenylpropylammonium iodide, we achieve devices with an efficiency of 17.5%, a radiance of 1282.8 W sr−1 m−2 and a record T50 half-lifetime of 130 h under 100 mA cm−2.

Halogen-halogen bonds enable improved long-term operational stability of mixed-halide perovskite photovoltaics

“…In normal 2D/3D perovskite film, suppressed PL shifting was observed, indicating that regular 2D/3D hybrid geometry does partially inhibit the ion migration due to the well-documented surface passivation effect. 47 However, PL shifting and FWHM (full width at half maximum) broaden still existed (Figure S19). On the contrary, the PL spectra remained almost unchanged over 40 min for the 2D/3D perovskite films with X-X bond, confirming that the interfacial halogen-halogen bonds significantly suppress the phase segregation.…”

Degradation and self-repairing in perovskite light-emitting diodes

“…We thus treat this key interface by 2-phenethylammonium iodide (PEAI) solutions. 47,48 To identify the functionality of PEAI treatment in the current case, we measure relative photoluminescence quantum yields (PLQYs) as a function of excitation fluence, as well as PL lifetime by TCSPC tests, of which the results are shown in Figure 5C and 5D respectively. Compared with that of ODEA-control samples, the PLQYs of PEAI-treated thin films are much higher at low excitations (below $3 mW cm À2 ) and almost independent upon excitation fluence ranging from $0.2 to $140 mW cm À2 .…”

Using steric hindrance to manipulate and stabilize metal halide perovskites for optoelectronics

“… 151 Guo et al passivated FAPbI 3 films with four kinds of phenylalkylammonium iodide molecules of different alkyl chain lengths (phenylmethylammonium iodide (PMAI, n = 1), phenethylammonium iodide (PEAI, n = 2), phenpropylammonium iodide (PPAI, n = 3), and phenylbutanammonium iodide (PBAI, n = 4)). 34 They found that the lifetime of PeLEDs is significantly improved with longer alkyl chain lengths ( Fig. 11c ).…”