Last October, the Nobel Prize in Chemistry was awarded to three researchers — Moungi Bawendi at the Massachusetts Institute of Technology, Louis Brus at Columbia University and Aleksey Yekimov at Nanocrystals Technology, a company based in New York — for the discovery and synthesis of quantum dots. These nanoscale semiconducting crystals have optoelectronic properties dominated by quantum-mechanical effects. As a result, the nanocrystals can be tuned to emit light of specific wavelengths by controlling their particle size.

Photograph of a 4 × 4 array of blue microLEDs wrapped around a cylindrical rod, which was fabricated using the site-selective integration strategy developed by Hong and colleagues. Credit: Hyungsoo Yoon and Sujin Jeong, Seoul National University

The materials have a range of potential applications — from medical imaging to solar cells — and are the basis of a growing global market that is already worth billions of US dollars each year. But it is their use in displays that is perhaps their most prominent application so far, with televisions containing quantum dots that have been commercially available since 2013.

In these commercial displays, the quantum dots use their photoluminescent properties and function as colour-converting films. Devices can, however, also be built using the electroluminescent properties of the materials, where emission is achieved with an electric current in a light-emitting diode (LED) configuration. Such systems could deliver even more powerful technology, from large-panel displays to virtual-reality headset screens. This application potential is highlighted in this issue of Nature Electronics, where Dae-Hyeong Kim and colleagues report the development of intrinsically stretchable quantum dot LEDs.

The researchers — who are based at various institutes in South Korea — create their devices from a mechanically soft and stretchable emissive layer that contains a ternary nanocomposite of colloidal quantum dots, an elastomeric polymer and a charge transport polymer. The resulting devices offer a high brightness of 15,170 cd m−2 at 6.2 V, which is sustained even under 50% strain. Kim and colleagues create full-colour passive-matrix arrays of the intrinsically stretchable quantum dot LEDs, which are also stable under different mechanical deformations.

Quantum dot LEDs are, of course, competing against a range of other next-generation display technologies. One of which is microLEDs1. Elsewhere in this issue, Yongtaek Hong and colleagues report a site-selective integration strategy for microdevices on conformable substrates, which they use to assemble arrays of microLEDs on various flexible substrates that can be bent and stretched.

The researchers — who are based at Seoul National University and Stanford University — use a dip-transfer coating technique to selectively pattern an adhesive precursor onto the surfaces of the microdevices. The adhesive contains ferromagnetic particles, which can be self-assembled into anisotropic chains using a magnetic field. This then provides a low contact resistance to interconnect the devices, and without electrical interference between fine-pitch terminals. As well as assembling flexible and stretchable arrays of microLEDs, the team show that the strategy can be used to create a skin-attachable device capable of detecting temperature and visualizing it on a microLED display.

Typically, a display’s only function is to display visual information, and additional sensors are then integrated into the devices to offer other functions such as touch control or ambient light sensing. However, photoresponsive LEDs, which can display information and respond to light excitation, could be used to create inherently multifunctional displays. In another Article elsewhere in this issue — and using another category of emerging LED technology — Feng Gao and colleagues report the development of displays based on photoresponsive metal halide perovskite LEDs.

Photoresponsive LEDs have been created before using quantum dots (incorporated into double-heterojunction nanorod structures)2, but a weak photoresponse limits wider application. The researchers — who are based at Linköping University, Nanjing University, Nanjing Tech University, Changzhou University, Westlake University and the University of Oxford — thus turned to perovskite LEDs, the performance of which has improved rapidly in recent years and can now offer bright emission and a high photoresponse.

The team use the perovskite LEDs to build a multifunctional display that functions as a touch screen, ambient light sensor and image sensor. They also show that the display can act as a photovoltaic device to charge the equipment. As Sebastian Fernández, Manchen Hu and Daniel Congreve of Stanford University explain in an accompanying News & Views article, there are, however, a number of issues that remain to be addressed before the technology can be considered commercially viable. In particular, Gao and colleagues create single-colour multifunctional displays, but the integration of sensing capabilities into full-colour red−green−blue displays will be an important next step.