Abstract
Electroluminescence in light-emitting devices relies on the encounter and radiative recombination of electrons and holes in the emissive layer. In organometal halide perovskite light-emitting diodes, poor film formation creates electrical shunting paths, where injected charge carriers bypass the perovskite emitter, leading to a loss in electroluminescence yield. Here, we report a solution-processing method to block electrical shunts and thereby enhance electroluminescence quantum efficiency in perovskite devices. In this method, a blend of perovskite and a polyimide precursor dielectric (PIP) is solution-deposited to form perovskite nanocrystals in a thin-film matrix of PIP. The PIP forms a pinhole-free charge-blocking layer, while still allowing the embedded perovskite crystals to form electrical contact with the electron- and hole-injection layers. This modified structure reduces nonradiative current losses and improves quantum efficiency by 2 orders of magnitude, giving an external quantum efficiency of 1.2%. This simple technique provides an alternative route to circumvent film formation problems in perovskite optoelectronics and offers the possibility of flexible and high-performance light-emitting displays.
Highlights
Electroluminescence in light-emitting devices relies on the encounter and radiative recombination of electrons and holes in the emissive layer
In this Letter, we report the fabrication of efficient lightemitting diodes through the embedding of perovskite nanocrystals in a thin matrix of dielectric polymer
We studied the morphology of the composite layer with various perovskite to polyimide precursor dielectric (PIP) ratios, using scanning electron microscopy (SEM)
Summary
While in the 1:10 ratio film (Figure 2h) the PIP polymer layer is incomplete in certain areas, the 1:2 ratio film in Figure 2i shows complete PIP polymer coverage with no signs of pinholes Through these SEM results, we can deduce that the perovskite nanocrystals form within a matrix of dielectric PIP in the blend films. These device studies and the SEM characterizations suggest that the 1:2 ratio film provides optimal PIP coverage and effectively blocks pinholes or electrical shunting paths. Because the perovskite and PIP composite devices emit efficiently and uniformly up to a 1:1 blend ratio, it is reasonable to assume that the perovskite nanocrystals extend across the thickness of these films, forming electrical contact with both the PEDOT:PSS and the F8 layers. This material is available free of charge via the Internet at http://pubs.acs.org
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