No abstract

We report acetamidinium (AA)-substituted methylammonium (MA) lead iodide perovskite solar cells. AA has a restricted C–N bond rotation because of delocalized π-electron cloud over the N–C–N bond and the presence of an additional N–H···I bond (4H-bond in AA as compared to 3H-bond in MA). These bonding structures strengthen the electrostatic interaction and stabilize the AA cation inside the perovskite matrix. AA, a larger cation, is substitutional only up to 10%. Devices made with 10% AA-substituted films show an average V oc of 1.12 V, higher than the average V oc of 1.04 V in the case of MA lead halide perovskite (MAPbI3). This increase in V oc can be attributed to an increase in carrier lifetime from 20 μs in the case of MAPbI3 to 32 μs for 10% AA-substituted films respectively. Devices with 18.29% champion and 16.3% average efficiency were fabricated for films with 10% AA. Degradation experiments confirm that the material stability also makes devices more stable; under ambient exposure (72 ± 3% RH), devices with 10% AA retain 70% of their initial power conversion efficiencies (PCEs) up to 480 h. Under the same conditions, the PCEs of reference MAPbI3 devices reduced to 43% of their initial value in 480 h.

communication, [4] environmental monitoring, [5] and wearable and neuromorphic computing. [6] This will also have an impact on the internet of things (IoT) where smart objects are wirelessly connected to interact with the environment and the human body. [7] The high-performing electronic devices made of compliant materials can add new capabilities in terms of highspeed communications, efficient image sensing, and so on. [4c,8] For example, the transmission rate, the transmission capacity, and the efficiency of wireless communication could significantly be enhanced if a single photodetector (PD) device could operate under wide spectra with low power consumption and latency. Furthermore, the demands for wide spectral switches [9] or memory storage [10] could be satisfied from the single PD. However, the studies so far have primarily focused on the development and characterization of high-performance flexible PDs under certain wavelength (i.e., UV, [1b,10,11] visible, [12] or NIR [13] spectrum). Recently, there have been few attempts to develop ultrafast and conformable broadband PDs. [8b,14] Among these, the heterostructures based on 2D materials and perovskites have shown potential to expand the working wavelength of PDs. [14] This is owing to their direct bandgap and large absorption coefficient. [15] Specifically, perovskites have garnered more interest for optoelectronic applications as they are solution processable and their fabrication cost is low. However, due to low mobility (≈1-10 cm 2 Vs) [16] and poor stability, [17] their performance metrics (e.g., responsivity [R] and specific detectivity [D*])) for PDs are modest. The poor stability in ambient conditions is attributed to the adsorption of water and oxygen molecules which greatly accelerate the degradation of the perovskite photosensitive layer. [15a] Efforts are ongoing to enhance the stability of perovskite-based devices exploring different encapsulations, but low intrinsic mobilities will still be a challenge. Thus, the efforts to develop next generation of flexible and high-performing PDs, with wide spectral sensitivity and robust fabrication route, are still on.In the above context, the nanostructures and thin films of inorganic compound semiconductors such as gallium arsenide (GaAs) have shown considerable potential for optoelectronic Nano/microstructures of compound semiconductors such as gallium arsenide (GaAs) demonstrate enormous potential for advanced photonic technologies as they provide realistic means for miniaturization of optoelectronic devices that feature better performance and low power consumption. However, intimately integrating them onto flexible substrates is challenging and restricts their use in the next generation of applications such as wearables and soft robotics. Herein, printed arrays of well-defined and laterally aligned semi-insulating (undoped) and doped GaAs microstructures are presented to develop high-performance flexible broadband photodetectors. The direct roll transfer printed GaAs microstructures-based ph...

Robotics has advanced tremendously from performing simple pick-and-place tasks in structured environments to operating in a range of real-world environments and terrains full of uncertainties. Often these advances have been motivated by biological systems. [1] As a result, the field has grown from simple robotic arms performing preprogrammed industrial tasks [2] to human/ animal-like robots or prosthetic devices that autonomously conduct wide-ranging tasks using various sensory modalities. [3][4][5] The advances in robotics have closely followed the developments in the fields of functional materials, sensing, actuation, and communication technologies, as well as artificial intelligence, which altogether have enabled robots to mimic the morphology and functionalities of biological systems to a high degree. [6] As an example, the implementation of large-area tactile skin or electronic skin (e-skin) has allowed robots to exploit tactile feedback from the whole body for working in unstructured or cluttered environments, just as animals do. [5,7] Likewise, miniaturized and yet powerful actuators and electronic components have allowed the development of dexterous hands and agile robots. [8] In recent years, 3D/4D printing has also opened the ways for the development of sensitized robots with complex shapes and soft structures. [9,10] Thus, advances in robotics have closely followed the technological advances in other areas such as electronic hardware, advanced materials, and manufacturing. However, there is one critical area where robotics appears to have largely missed to follow the technological trend, i.e., the energy needed to power the robots.A reliable source of energy is critical for the smooth operation of autonomous robots, particularly in environments where mains power is not readily available. In fact, the majority of applications today require robots to be autonomous, and as such, they must rely wholly on batteries for their source of power. Analyzing the state of the art, we note that not much progress has been made in terms of adopting the advanced energy solutions in the robot, despite major advances in battery technology. [11] Starting from the first autonomous wheel-based robot Shakey [12] in 1966 to the state-of-the-art humanoid robots developed during the last 30 years and the quadrupedal MIT cheetah robot [13] of 2018, the battery the autonomous robots use has improved only in terms of light weight and energy density (Figure 1). [14][15][16] In contrast, the energy-storage technology itself has evolved from the bulky and leaky liquid electrolyte-based systems [17,18] to printed batteries, flexible supercapacitors (SCs) with safe electrolytes, and elegant textile-based devices. [19][20][21][22] The battery technology has improved in terms of a Watt-to-weight ratio, form factors, lifetime, ruggedness (thermal and chemical), etc., and nowadays, flexible, stretchable, and printed batteries are increasingly being explored.The energy requirement of robots can also be met with the harvesting of renewa...

No abstract