Tuning the Emission Wavelength of Lead Halide Perovskite NCs via Size and Shape Control.

The advent of lead halide perovskite nanocrystals (NCs), which are easily synthesized, ultralow-cost materials and have an impeccable luminous efficiency, has drastically changed the future perspective of semiconductor quantum dot devices. Although the band gap energy of lead perovskite NCs can be tuned by the halide composition, the instability problem prevails for mixed-halide perovskite NCs, caused by phase segregation due to ion migration when an external electric field or light is applied. To avoid this problem and obtain the stable emission of RGB primary colors, in this study, two synthesis pathways of pure-halide perovskite NCs are proposed.

All-inorganic perovskite quantum dot light-emitting memories.

Field-induced ionic motions in all-inorganic CsPbBr perovskite quantum dots (QDs) strongly dictate not only their electro-optical characteristics but also the ultimate optoelectronic device performance. Here, we show that the functionality of a single Ag/CsPbBr/ITO device can be actively switched on a sub-millisecond scale from a resistive random-access memory (RRAM) to a light-emitting electrochemical cell (LEC), or vice versa, by simply modulating its bias polarity. We then realize for the first time a fast, all-perovskite light-emitting memory (LEM) operating at 5 kHz by pairing such two identical devices in series, in which one functions as an RRAM to electrically read the encoded data while the other simultaneously as an LEC for a parallel, non-contact optical reading.

Thermodynamic Control in the Synthesis of Quantum-Confined Blue-Emitting CsPbBr Perovskite Nanostrips.

Size control is critical in the synthesis of quantum-confined semiconductor nanocrystals, otherwise known as quantum dots. The achievement of size-uniformity and narrow spectral line-width in quantum dots conventionally relies on a very precise kinetic control of the reactions, where reaction time plays a significant role in defining the final crystal sizes and distribution. Here, we show that synthesis of quantum-confined perovskite nanostrips could be achieved through a thermodynamically controlled reaction, using a low-temperature and ligand-rich approach.