Tsao, Hoi Nok

Power sources that can be charged anytime and anywhere are highly desirable for mobile devices. The most suitable device for achieving such wireless charging is a photocapacitor, which utilizes light as a renewable energy source instead of electricity from the grid. Sunlight on Earth is intermittent and unstable, so photocapacitors that can be charged by the day or room light and near-infrared (near-IR) radiation are needed to ensure the uninterrupted operation of the equipment. We employ a single dye-sensitized solar cell as a photocapacitor without adding any additional charge storage components to reduce the cost and complexity of device manufacturing. To realize such photocapacitors, this work presents a family of new isoindigo-based D-π-A photoactive dyes with good visible and near-IR absorption. Notably, LF15 has a higher molar absorbance coefficient and enhanced dye-loading than LF23, which is consistent with the higher photocurrent of photocapacitors based on the former. Photocapacitors based on these three dyes achieve photovoltages up to 0.74 V, area-specific capacitances of 2.87 mF cm−2, and excellent charge-discharge stability. The devices can be charged in both visible and near-IR conditions, exhibiting typical capacitor behavior.

Convolutional neural networks (CNNs) have attracted much attention in recent years due to their outstanding performance in image classification. However, changes in lighting conditions can corrupt image segmentation conducted by CNN, leading to false object detection. Even though this problem can be mitigated using a more extensive CNN training set, the immense computational and energy resources required to continuously run CNNs during always-on applications, such as surveillance or self-navigation, pose a serious challenge for battery-reliant mobile systems. To tackle this longstanding problem, a vision sensor capable of autonomously correcting for sudden variations in light exposure, without invoking any complex object detection software, is proposed. Such video preprocessing is efficiently achieved using photovoltaic pixels tailored to be insensitive to specific ranges of light intensity alterations. In this way, the pixels behave similarly to neurons, wherein the execution of object detection software is only triggered when light intensities shift above a certain threshold value. This proof-of-concept device allows for efficient fault-tolerant object detection to be implemented with reduced training data as well as minimal energy and computational costs and demonstrates how hardware engineering can complement software algorithms to improve the overall energy efficiency of computer vision.

Organic light-emitting transistors (OLET) evolved from the fusion of switching functionality of the field-effect transistors (FET) with the light-emitting characteristics of the organic light-emitting diode (OLED) that can simplify the active-matrix pixel device architecture and hence offer a promising pathway for future flat panel and flexible display technology. This review systematically analyses the key device/molecular engineering tactics that assisted in improving the electrode edge narrow emission to wide-area emission for display applications via three different topics such as narrow to area emission, vertical architecture, and impact of high-🇰 dielectric on the device performance. Source-drain electrode engineering such as symmetric/asymmetric, planar/non-planar arrangement, semitransparent nature, multilayer approach comprising charge transport and work function modification layers assisted in improving the thin line emission to area emission. Vertical OLET architecture offers short channel lengths with a high aperture ratio, pixel type area emission, and stable light emitting area. Transistors utilizing high-🇰 dielectric materials assisted in lowering the operating voltage, enhancing the luminance and air stability. The promising development in achieving wide area emission provides a strong basis for constructing OLET research towards display applications; however, it relies on the development of highly luminescent and fast charge transporting materials, suitable semitransparent source/drain electrodes, high-🇰 -dielectrics, and device architectural engineering.

Optoelectronic devices based on perovskite materials have shown significant improvement due to the direct and tunable bandgaps, large absorption coefficients, broad absorption spectra, high carrier mobilities, and long carrier diffusion lengths. In addition to the excellent performance in solar cells, scientists have utilized perovskite materials for other optoelectronic applications as well. This review details the figures‐of‐merit and the development of perovskite‐based photodetectors, including UV to NIR detection and high energy particle sensing. Discussions are made based on different device structures. Furthermore, gas, compound, temperature, and pressure sensors using perovskite materials are reviewed. “Miscellaneous” functionality and “perspicacious” performance have been achieved with these devices.