(171c) Layer-Controlled Colloidal Dispersions of Two-Dimensional Organometal Halide Perovskites for Efficient Blue Light-Emitting Diodes

Layer-Controlled
Colloidal Dispersions of Two-Dimensional Organometal Halide Perovskites for
Efficient Blue Light-Emitting Diodes

Jakub
Jagielski, Sudhir Kumar, and Chih-Jen Shih*

Institute for Chemical and
Bioengineering, DCHAB,
ETH Zurich, Zurich, Switzerland

*Author to whom all correspondence should be
addressed.  Email: chih-jen.shih@chem.ethz.ch

Abstract

Two-dimensional (2D) organometal halide perovskites exhibit the quantum
confinement effect by reducing the thickness smaller than the Bohr radius, or
~10 unit cell thick (i.e., n <
10). Their colloidal dispersion is emerging as one of the most promising
candidates for printable optoelectronics and nanocomposites. However, it is not
yet possible to synthesize large quantities of high-photoluminescence-quantum-yield
(PLQY > 20%) 2D perovskites with precisely controlled stacking, as is
necessary for light-emitting diodes (LEDs). Here, we demonstrate a synthesis
method for the large-scale production of monolayer (n = 1), trilayer (n = 3),
and 5-layer (n = 5) 2D methylammonium
lead bromide (MAPbBr₃) colloidal dispersions, which exhibit blue PL
emissions at ~431 nm, ~456 nm, and ~485 nm, respectively, with high PLQYs (50%
- 80%). The carefully-controlled ligand chemistry allows small lateral size and
surface passivation, minimizing the effects of self-quenching and downhill
energy transfer. The high PLQY has led to a record-high external quantum
efficiency (EQE) of 0.2% in the blue LED devices, representing a >500-fold
increase compared to that of the best blue organometal halide perovskite LED
reported so far. The solution-based process is expected to allow low-cost and
high-throughput production, as well as the deposition of the new family of 2D
materials onto arbitrary substrates.