Recently,
surface passivation has been proved to be an essential
approach for obtaining efficient and stable perovskite light-emitting
diodes (Pero-LEDs). Phosphine oxides performed well as passivators
in many reports. However, the most commonly used phosphine oxides
are insulators, which may inhibit carrier transport between the perovskite
emitter and charge-transporter layers, limiting the corresponding
device performance. Here, 2,7-bis(diphenylphosphoryl)-9,9′-spirobifluorene
(SPPO13), a conductive molecule with two phosphine oxide functional
groups, is introduced to modify the perovskite emitting layer. The
bifunctional SPPO13 can passivate the nonradiative defects of perovskite
and promote electron injection at the interface of perovskite emitter
and electron-transporter layers. As a result, the corresponding Pero-LEDs
obtain a maximum external quantum efficiency (EQE) of 22.3%. In addition,
the Pero-LEDs achieve extremely high brightness with a maximum of
around 190 000 cd/m2.
Metal halide perovskite films are prepared mainly by
solution-based
methods. However, the preparation process is prone to produce massive
defects at the interface between the perovskite emitting layer and
the charge transport layers, limiting the perovskite light-emitting
diode device performance. Aiming at this problem, researchers have
proposed many effective strategies to passivate these interface defects.
However, most previous research studies only focus on modifying the
perovskite top interface, and very few reports deal with the buried
interface. Here, we deposited triphenylphosphine oxide (TPPO) molecules
between the perovskite and the hole transport layer (HTL) and realized
the buried interface modification. Adding TPPO avoids the contact
recombination of the perovskite and HTL and improves the film quality
by increasing the substrate wettability. Moreover, the lone pair electrons
of PO can interact with the uncoordinated lead (Pb2+) of the perovskite and passivate halogen vacancy defects, and the
insulation property of TPPO helps to balance the injection of holes
and electrons. As a result, a maximum external quantum efficiency
(EQEmax
) of 21.01% was obtained with an
average of 18.4 ± 0.9% over 30 devices, and the device reproducibility
was greatly enhanced.
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