High-speed underwater optical wireless communication (UOWC) was achieved using an 80 μm blue-emitting GaN-based micro-LED. The micro-LED has a peak emission wavelength of ~440 nm and an underwater power attenuation of 1 dB/m in tap water. The -3 dB electrical-to-optical modulation bandwidth of the packaged micro-LED increases with increasing current and saturates at ~160 MHz. At an underwater distance of 0.6 m, 800 Mb/s data rate was achieved with a bit error rate (BER) of 1.3 × 10^-3, below the forward error correction (FEC) criteria. And we obtained 100 Mb/s data communication speed with a received light output power of -40 dBm and a BER of 1.9 × 10^-3, suggesting that UOWC with extended distance can be achieved. Through reflecting the light emission beam by mirrors within a water tank, we experimentally demonstrated a 200 Mb/s data rate with a BER of 3.0 × 10^-6 at an underwater distance of 5.4 m.

Organic optoelectronic devices are usually driven by the electric field generated from an electrode potential difference or bias voltage. Although poled ferroelectric domains may produce oriented stray fields, few efforts have been made to utilize them for photocurrent generation in organic devices. Here we show that large net fields caused by incomplete screening during ferroelectric polarization, and which can be 'restored' by short voltage pulses, can facilitate exciton dissociation in organic semiconductors. The oriented fields, comparable with that produced by an electrode potential difference (1B10 MV m À 1 ), here are found to be responsible for the photocurrent in our devices. A prototype for an organic photodetector driven by such stray fields is demonstrated. The photoresponsivity, without any optimization, can achieve B0.1 mA W À 1 . This study provides a different operation principle for the generation of photocurrent in organic optoelectronic devices. Furthermore, the polarity-tunable photoresponse may lead to new photoresponsive memory devices.

Two-dimensional heterojunctions exhibit many unique features in nanoelectronic and optoelectronic devices. However, heterojunction engineering requires a complicated alignment process and some defects are inevitably introduced during material preparation. In this work, a laser scanning technique is used to construct a lateral WSe2 p–n junction. The laser-scanned region shows p-type behavior, and the adjacent region is electrically n-doped with a proper gate voltage. The laser-oxidized product WO x is found to be responsible for this p-type doping. After laser scanning, WSe2 displays a change from ambipolar to unipolar p-type property. A significant photocurrent emerges at the p–n junction. Therefore, a self-powered WSe2 photodetector can be fabricated based on this junction, which presents a large photoswitching ratio of 106, a high photoresponsivity of 800 mA W–1, and a short photoresponse time with long-term stability and reproducibility. Therefore, this selective laser-doping method is prospective in future electronic applications.

Fully interactive: Overlap between extended unoccupied molecular orbitals leads to the high photoconductivity of interactive radical dimers. Sandwich-type cells (see picture; ITO = indium tin oxide) comprising highly oriented thin films of a disjoint diradical, 4,4'-bis(1,2,3,5-dithiadiazolyl) (BDTDA) exhibit a photocurrent with a high on/off ratio at reverse bias voltages and photovoltaic behavior at zero bias voltage.