Good Co‐op: A novel cyclopentadithiophene‐bridged donor–acceptor dye applied as sensitizer in mesoscopic dye‐sensitized solar cells, in conjunction with the cobalt complexes CoII(bpy)3(B(CN)4)2 and ...CoIII(bpy)3(B(CN)4)3 as redox couple, yields high power conversion efficiencies (up to 9.6 %) under standard AM 1.5G solar irradiation. The results confirm that cobalt complexes are legitimate alternatives to the commonly used I−/I3− redox shuttle when used with judiciously engineered organic sensitizers.
The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co (II/III) tris(bipyridyl)—based ...redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.
A replacement for gold as the hole‐injecting metal in organic electronic devices is presented: patterned graphene electrodes prepared from graphite oxide sheets by oxygen plasma etching. ...Solution‐processed organic FETs with poly(3‐hexylthiophene) as the semiconductor and these graphene electrodes are shown to perform as well as or even better than devices with gold contacts.
The influence of molecular packing on the performance of polymer organic field‐effect transistors is illustrated in this work. Both close π‐stacking distance and long‐range order are important for ...achieving high mobilities. By aligning the polymers from solution, long‐range order is induced, yielding hole mobilities of up to µsat = 1.4 cm2 V−1 s−1 and current on/off ratios Ion/Ioff of 105.
A prominent problem in computer vision is occlusion, which occurs when an object's key features temporarily disappear behind another crossing body, causing the computer to struggle with image ...detection. While the human brain is capable of compensating for the invisible parts of the blocked object, computers lack such scene interpretation skills. Cloud computing using convolutional neural networks is typically the method of choice for handling such a scenario. However, for mobile applications where energy consumption and computational costs are critical, cloud computing should be minimized. In this regard, a computer vision sensor capable of efficiently detecting and tracking covered objects without heavy reliance on occlusion‐handling software is proposed. The edge‐computing sensor accomplishes this task by self‐learning the object prior to the moment of occlusion and uses this information to “reconstruct” the blocked invisible features. Furthermore, the sensor is capable of tracking a moving object by predicting the path it will most likely take while traveling out of sight behind an obstructing body. Finally, sensor operation is demonstrated by exposing the device to various simulated occlusion events. An interactive preprint version of the article can be found at DOI https://www.authorea.com/doi/full/10.22541/au.164192000.02603887/.
An AI‐accelerating computer vision sensor is presented that is capable of detecting and tracking occluded objects.
Dye‐sensitized solar cells based on electrolytes containing cobalt complexes as redox shuttles typically suffer a major limitation in terms of slow diffusion of those couples through the mesoporous ...TiO2 film. This results in a drop of the photocurrent density, particularly at high incident light intensities, reducing the overall cell performance. This work illustrates how tuning the four characteristic parameters of the mesoporous TiO2 layer, namely film thickness, particle size, pore size and porosity, by simply optimizing the TiCl4 post‐treatment, completely eliminates diffusion problems of cobalt(III/II) tris(2,2′‐bipyridine) and at the same time maximizes the short‐circuit photocurrent density. As a result, a power conversion efficiency of 10.0 % at AM 1.5 G 100 mW cm−2 was reached in conjunction with an organic sensitizer.
At the limit: It is illustrated how diffusion limitations of cobalt redox couples in dye‐sensitized solar cells (see picture) can be eliminated by tuning the porosity, particle and pore sizes of the mesoporous TiO2 layers through simple TiCl4 post‐treatment. Thus, thicker TiO2 films required for higher photocurrent densities can be used without encountering mass transport limitations, leading to power conversion efficiencies of 10 %.
We designed and synthesized two new zinc porphyrin dyes for dye‐sensitized solar cells (DSCs). Subtle molecular structural variation in the dyes significantly influenced the performance of the DSC ...devices. By utilizing these dyes in combination with a cobalt‐based redox electrolyte using a photoanode made of mesoporous TiO2, we achieved a power conversion efficiency (PCE) of up to 12.0 % under AM 1.5 G (100 mW cm−2) simulated solar light. Moreover, we obtained a high PCE of 6.4 % for solid‐state dye‐sensitized solar cells by using 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene as a hole‐transporting material.
Dying to live: Subtle molecular structural variations in two zinc porphyrin dyes significantly influence the performance of dye‐sensitized solar cell devices. By utilizing the dyes in combination with a cobalt‐based redox electrolyte, a high power conversion efficiency (PCE) under simulated solar light is achieved. When using spiro‐OMeTAD as the hole‐transporting material in solid‐state solar cells, the highest PCE for such a device until now is observed.
Two D-π-A dyes based on fused acenes（carbazole, cyclopenta2,1-b：3,4-b＇dithiophene（CPDT） and dithieno3,2-b：2＇,3＇-dpyrrole（DTP）） were synthesized, characterized using UV-vis absorption spectroscopy and ...electrochemistry, density function theory（DFT） calculations, and used as sensitizers in dyesensitized solar cells（DSSCs）. The two sensitizers were compared thoroughly over physicochemical properties and DSSC performance. Although the DTP dye has slightly blue-shifted and weaker incident photon-to-collected electron（IPCE） conversion efficiency responses, the much increased open-circuit photovoltage values and improved charge-transfer kinetics relative to the CPDT systems result in superior power conversion efficiencies. This work reveals the potential of DTP as a bridge in the design of sensitizers.
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.
Correctly detecting objects under varying lighting conditions is a core problem in computer vision. Herein, a video preprocessing optoelectronic sensor capable of autonomously correcting for sudden changes in light exposure is presented, enabling fault‐tolerant object detection to be implemented with minimal energy and computational costs.
Organic light‐emitting transistors (OLET) evolved from the fusion of the switching functionality of field‐effect transistors (FET) with the light‐emitting characteristics of 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 analyzes the key device/molecular engineering tactics that assist in improving the electrode edge narrow emission to wide‐area emission for display applications via three different topics, that is, narrow to wide‐area emission, vertical architecture, and impact of high‐κ 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 enable widening the emission zone. Vertical OLET architecture offers short channel lengths with a high aperture ratio, pixel type area emission, and stable light‐emitting area. Transistors utilizing high‐κ dielectric materials have assisted in lowering the operating voltage, enhancing luminance and air stability. The promising development in achieving wide‐area emission provides a solid basis for constructing OLET research toward display applications; however, it relies on developing highly luminescent and fast charge transporting materials, suitable semitransparent source/drain electrodes, high‐κ ‐dielectrics, and device architectural engineering.
The fusion of light‐emitting OLED technology with the switching functionality of OFET in a single device provokes a new research direction, organic light‐emitting transistors (OLET). This review summarizes the progress of OLET for their potential applications toward display technology via three promising tactics such as narrow to wide‐area emission, vertical architecture, and impact of high‐κ dielectrics.
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