The emergence of wearable electronics and optoelectronics requires the development of devices that are not only highly flexible but can also be woven into textiles to offer a truly integrated solution. Here, we report a colour-tunable, weavable fibre-shaped polymer light-emitting electrochemical cell (PLEC). The fibre-shaped PLEC is fabricated using all-solutionbased processes that can be scaled up for practical applications. The design has a coaxial structure comprising a modified metal wire cathode and a conducting aligned carbon nanotube sheet anode, with an electroluminescent polymer layer sandwiched between them. The fibre shape offers unique and promising advantages. For example, the luminance is independent of viewing angle, the fibre-shaped PLEC can provide a variety of different and tunable colours, it is lightweight, flexible and wearable, and it can potentially be woven into light-emitting clothes for the creation of smart fabrics. L ight-emitting electrochemical cells 1-6 , in particular polymer light-emitting electrochemical cells (PLECs), have been widely studied for various applications, including flexible flat panel displays, signage and lighting 4-6 . Like organic light-emitting diodes (OLEDs) and polymer light-emitting diodes (PLEDs), PLECs have a structure that is usually composed of two metal electrodes connected to an organic semiconductor. However, PLECs differ in that mobile ions are incorporated into the organic semiconductor, thereby offering promising advantages such as low operating voltage, high electron/photon conversion efficiency and high power efficiency compared with OLEDs 7-18 . More importantly, PLECs do not require the use of low-workfunction cathodes composed of calcium or magnesium (which are sensitive in air). In contrast, PLEDs require a low-workfunction cathode and high-workfunction anode to realize efficient charge injection 19-21 . In a typical PLEC, the electroluminescent polymer layer forms an in situ light-emitting p-i-n junction for the injection of both electrons and holes from the electrodes 4,5,22 . This means that PLECs can be effectively operated with relatively rougher surfaces than is generally possible with OLEDs and PLEDs, which is advantageous when scaling them up for practical applications with low cost and high efficiency 23-25 .Based on these described advantages, the PLEC is particularly promising for use in portable and wearable electronics, which are being developed for a wide range of applications, from microelectronics to biomedicine, transport and areospace 26-32 . Conventional planar light-emitting devices, including both rigid and flexible films, cannot satisfy the basic requirements for such an application, including softness, light weight and weavability 33,34 . To this end, advances in the textile industry have suggested a useful direction in which to pursue a solution: if a PLEC is made into a continuous fibre using a melting or all-solution-based process, it can be woven into various flexible textiles or integrated into soft substrates for u...

An unusual increase in the Seebeck coefficient with increasing charge carrier density is observed in pentacene thin film transistors. This behavior is interpreted as being due to a transition from hopping transport in static localized states to bandlike transport, occurring at temperatures below ∼250  K. Such a transition can be expected for organic materials in which both static energetic disorder and dynamic positional disorder are important. While clearly visible in the temperature and density dependent Seebeck coefficient, the transition hardly shows up in the charge carrier mobility.

Emphasis was recently placed on the Cs2AgBiBr6 double perovskite as a possible candidate to substitute toxic lead in metal halide perovskites. However, its poor light-emissive features currently make it unsuitable for solid-state lighting. Lanthanides doping is an established strategy to implement luminescence in poorly emissive materials, with the additional advantage of fine-tuning the emission wavelength. We discuss here the impact of Eu-and Yb-doping on the optical properties of Cs2AgBiBr6 thin films, obtained from solution-processing of hydrothermally synthesized bulk crystalline powders, by combining experiments and density functional theory calculations. Eu(III) incorporation does not lead to the characteristic 5 D0→ 7 F2 emission feature at 2 eV, while only a weak trap-assisted sub band-gap radiative emission is reported. Oppositely, we demonstrate that incorporated Yb(III) leads to an intense and exclusive photoluminescence emission in the nearinfrared as a result of the efficient sensitization of the lanthanide 2 F5/2→ 2 F7/2 transition.

A flexible electroluminescent fiber was developed by incorporating two coaxially wound carbon nanotube sheet electrodes with an active polymer sandwiched between them.