Polymer-Free Films of Inorganic Halide Perovskite Nanocrystals as UV-to-White Color-Conversion Layers in LEDs.

Abstract

Being considerably more efficient than traditional incandescent bulbs or fluorescent tubes, light-emitting diodes (LEDs) are becoming the main technology for general lighting applications.1,2 In the last years, a variety of white-LEDs have been demonstrated employing, for example, organic molecules (OLEDs)3−7 or inorganic quantum dots (QDs) of different composition.8 A common way of achieving a white-light emission is to couple a near-UV or blue LED with down-conversion materials such as phosphors.9 More recently, QDs have been incorporated into LEDs, replacing conventional phosphors to tune finely the emission spectrum.10 Among the different available QDs, lead halide-based perovskite nanocrystals have recently emerged as very promising candidates for many optoelectronic applications.11−15 Colloidal perovskite nanocrystals can be synthesized and/or transformed postsynthesis, so that samples emitting at different wavelengths throughout the whole visible spectrum, with high photoluminescence quantum yield (PLQY), can be prepared easily. This can be achieved either by changing the chemical composition (by anion-exchange for example)16,17 or the shape (cubes, platelets, sheets, wires).18−21 Also, electroluminescence has been observed from bulk perovskite films,22−25 blended perovskite-in-polymer films,26 as well as from nanocrystals-only films27,28 leading to the first perovskite-based LEDs.