Improving the ohmic contact and interfacial morphology between an electron transport layer (ETL) and perovskite film is the key to boost the efficiency of planar perovskite solar cells (PSCs). In the ...current work, an amorphous–crystalline heterophase tin oxide bilayer (Bi‐SnO2) ETL is prepared via a low‐temperature solution process. Compared with the amorphous SnO2 sol–gel film (SG‐SnO2) or the crystalline SnO2 nanoparticle (NP‐SnO2) counterparts, the heterophase Bi‐SnO2 ETL exhibits improved surface morphology, considerably fewer oxygen defects, and better energy band alignment with the perovskite without sacrificing the optical transmittance. The best PSC device (active area ≈ 0.09 cm2) based on a Bi‐SnO2 ETL is hysteresis‐less and achieves an outstanding power conversion efficiency of ≈20.39%, which is one of the highest efficiencies reported for SnO2‐triple cation perovskite system based on green antisolvent. More fascinatingly, large‐area PSCs (active areas of ≈3.55 cm2) based on the Bi‐SnO2 ETL also achieves an extraordinarily high efficiency of ≈14.93% with negligible hysteresis. The improved device performance of the Bi‐SnO2‐based PSC arises predominantly from the improved ohmic contact and suppressed bimolecular recombination at the ETL/perovskite interface. The tailored morphology and energy band structure of the Bi‐SnO2 has enabled the scalable fabrication of highly efficient, hysteresis‐less PSCs.
The amorphous–crystalline heterophase SnO2 electron transport bilayer (Bi‐SnO2) exhibits improved surface morphology, fewer oxygen defects, and better energy band alignment with the perovskite, which enables more efficient electron extraction. The use of Bi‐SnO2 boosts the efficiency of small‐area (0.09 cm2) and large‐area (3.55 cm2) perovskite solar cells up to 20.39% and 14.93%, respectively.
A flexible pressure sensor with high performances is one of the promising candidates for achieving electronic skins (E‐skin) related to various applications such as wearable devices, health ...monitoring systems, and artificial robot arms. The sensitive response for external mechanical stimulation is fundamentally required to develop the E‐skin which imitates the function of human skin. The performance of capacitive pressure sensors can be improved using morphologies and structures occurring in nature. In this work, highly sensitive capacitive pressure sensors based on a porous structure of polydimethylsiloxane (PDMS) thin film, inspired on the natural multilayered porous structures seen in mushrooms, diatoms, and spongia offilinalis, have been developed and evaluated. A bioinspired porous dielectric layer is used, resulting in high‐performance pressure sensors with high sensitivity (0.63 kPa−1), high stability over 10 000 cycles, fast response and relaxation times, and extremely low‐pressure detection of 2.42 Pa. Additionally, the resulting pressure sensors are demonstrated to fabricate multipixel arrays, thus achieving successful real‐time tactile sensing of various touch shapes. The developed high‐performance flexible pressure sensors may open new opportunities for innovative applications in advanced human‐machine interface systems, robotic sensory systems, and various wearable health monitoring devices.
A highly sensitive bioinspired porous structured pressure sensor is demonstrated that can detect extremely light weight objects such as an ant. The porous structured pressure sensor is pixelated into a 15 × 15 array and based on the fast response time of the pressure sensor, real‐time tactile mapping is demonstrated under various pressures.
Solution‐processed triple‐cation perovskite solar cells (PSCs) rely on complex compositional engineering or delicate interfacial passivation to balance the trade‐off between cell efficiency and ...long‐term stability. Herein, the facile fabrication of highly efficient, stable, and hysteresis‐free tin oxide (SnO2)‐based PSCs is demonstrated with a champion cell efficiency of 20.06% using a green, halogen‐free antisolvent. The antisolvent, composed of ethyl acetate (EA) solvent and hexane (Hex) in different proportions, works exquisitely in regulating perovskite crystal growth and passivating grain boundaries, leading to the formation of a crack‐free perovskite film with enlarged grain size. The high quality perovskite film inhibits carrier recombination and substantially improves the cell efficiency, without requiring an additional enhancer/passivation layer. Furthermore, these PSCs also demonstrate remarkable long‐term stability, whereby unencapsulated cells exhibit a power conversion efficiency (PCE) retention of ≈71% after >1500 hours of storage under ambient condition. For encapsulated cells, an astounding PCE retention of >98% is recorded after >3000 hours of storage in air. Overall, this work realizes the fabrication of SnO2‐based PSCs with a performance greater or comparable to the state‐of‐the‐art PSCs produced with halogenated antisolvents. Evidently, EA–Hex antisolvent can be an extraordinary halogen‐free alternative in maximizing the performance of PSCs.
Eliminating the use of toxic, halogenated antisolvents in perovskite film preparation has been long desired. This work demonstrates the use of a halogen‐free, mixed antisolvent composed of ethyl acetate and hexane to boost the efficiency of tin oxide (SnO2)–triple cation system beyond 20% without the use of an additional passivation layer.
While a majority of wireless microrobots have shown multi‐responsiveness to implement complex biomedical functions, their functional executions are strongly dependent on the range of stimulus inputs, ...which curtails their functional diversity. Furthermore, their responsive functions are coupled to each other, which results in the overlap of the task operations. Here, a 3D‐printed multifunctional microrobot inspired by pollen grains with three hydrogel components is demonstrated: iron platinum (FePt) nanoparticle‐embedded pentaerythritol triacrylate (PETA), poly N‐isopropylacrylamide (pNIPAM), and poly N‐isopropylacrylamide acrylic acid (pNIPAM‐AAc) structures. Each of these structures exhibits their respective targeted functions: responding to magnetic fields for torque‐driven surface rolling and steering, exhibiting temperature responsiveness for on‐demand surface attachment (anchoring), and pH‐responsive cargo release. The versatile multifunctional pollen grain‐inspired robots conceptualized here pave the way for various future medical microrobots to improve their projected performance and functional diversity.
A multifunctional hydrogel microrobot is created by different stimuli‐responsive hydrogels with pollen grain‐inspired microstructures. The robot is capable of conducting temperature‐responsive on‐demand surface attachment, magnetic locomotion, and pH‐responsive cargo delivery toward biomedical applications.
Transparent conducting electrodes (TCEs) have played a pivotal role in driving the continuous development of optoelectronics technologies, which include organic optoelectronic applications. In recent ...years, there has been huge interest in designing innovative TCEs to replace the conventional indium tin oxide (ITO) electrodes, which suffer from complex fabrication issues and are incompatible with flexible, wearable electronic devices. In this regard, TCEs based on metal meshes are considered to be the best candidates because of their inherently high electrical conductivity, optical transparency, mechanical robustness and, more importantly, cost-competitiveness. In this review, we describe the technology developments of metal mesh-based transparent conductors and their applications in organic optoelectronic devices, including organic and perovskite solar cells, organic light emitting diodes, supercapacitors, electrochromic devices etc. Specifically, we discuss the fundamental features, optoelectronic properties, fabrication techniques and device applications of metal mesh TCEs. We also highlight the important criteria for evaluating the performance of metal mesh electrodes and propose some new research directions in this emerging field.
Fabrication strategies that pursue “simplicity” for the production process and “functionality” for a device, in general, are mutually exclusive. Therefore, strategies that are less expensive, less ...equipment‐intensive, and consequently, more accessible to researchers for the realization of omnipresent electronics are required. Here, this study presents a conceptually different approach that utilizes the inartificial design of the surface roughness of paper to realize a capacitive pressure sensor with high performance compared with sensors produced using costly microfabrication processes. This study utilizes a writing activity with a pencil and paper, which enables the construction of a fundamental capacitor that can be used as a flexible capacitive pressure sensor with high pressure sensitivity and short response time and that it can be inexpensively fabricated over large areas. Furthermore, the paper‐based pressure sensors are integrated into a fully functional 3D touch‐pad device, which is a step toward the realization of omnipresent electronics.
High‐performance paper‐based pressure sensors are developed through inartificial design of the surface curl and roughness of paper and graphite. The proposed approach involves writing on paper with a pencil, and the sensors can be inexpensively fabricated over a large area. The paper‐based pressure sensors are integrated into a fully functional 3D touch‐pad device, which is a step toward the realization of advanced paper electronics.
The popularity of wearable smart electronic gadgets, such as smartphones, smartwatches, and medical sensors, is inhibited by their limited operation lifetime due to the lack of a sustainable ...self‐charging power supply. This constraint can be overcome by developing a flexible, self‐charging photocapacitor that can synchronously harvest and store energy. Here, ultrathin, all‐printed, and metal‐embedded transparent conducting electrodes (ME‐TCEs) are designed for the fabrication of large‐area, flexible organic solar cells (F‐OSCs) and flexible supercapacitors (F‐SCs). Stripe‐shaped F‐OSCs (SF‐OSCs) and F‐SCs (SF‐SCs) are obtained via slitting the as‐fabricated F‐OSCs and F‐SCs with a surgical scalpel, respectively. The SF‐OSCs and SF‐SCs fully retain their performance after slitting, achieving a power conversion efficiency of ≈6.43% and areal capacitance of ≈52 mF cm−2, respectively. Furthermore, photocapacitor fibers are obtained by vertically stacking one SF‐OSC and seven SF‐SCs. Each fiber is fully encapsulated using UV‐curable resin. When woven into a textile, the photocapacitor module (2 series × 4 parallel connections) is able to charge up to a voltage of 3.2 V in 5 min under one‐sun illumination. The photoelectric‐conversion‐and‐storage efficiency (η) of the photocapacitor module is 4.94%. The highly tailorable, mechanically robust photocapacitor demonstrated herein can be a secondary, self‐sustainable power supply for futuristic wearable applications.
1D, wearable photocapacitor fibers are prepared by stacking one stripe‐shaped organic solar cells and seven stripe‐shaped supercapacitors in tandem. A self‐charging module is then constructed by connecting eight photocapacitor fibers in a 2 series × 4 parallel circuit, yielding a photo‐conversion‐and‐storage efficiency of 4.94%.
2D tin‐based perovskites have gained considerable attention for use in diverse optoelectronic applications, such as solar cells, lasers, and thin‐film transistors (TFTs), owing to their good ...stability and optoelectronic properties. However, their intrinsic charge‐transport properties are limited, and the insulating bulky organic ligands hinder the achievement of high‐mobility electronics. Blending 3D counterparts into 2D perovskites to form 2D/3D hybrid structures is a synergistic approach that combine the high mobility and stability of 3D and 2D perovskites, respectively. In this study, reliable p‐channel 2D/3D tin‐based hybrid perovskite TFTs comprising 3D formamidinium tin iodide (FASnI3) and 2D fluorinated 4‐fluoro‐phenethylammonium tin iodide ((4‐FPEA)2SnI4) are reported. The optimized FPEA‐incorporated TFTs show a high hole mobility of 12 cm2 V−1 s−1, an on/off current ratio of over 108, and a subthreshold swing of 0.09 V dec−1 with negligible hysteresis. This excellent p‐type characteristic is compatible with n‐type metal‐oxide TFT for constructing complementary electronics. Two procedures of antisolvent engineering and device patterning are further proposed to address the key concern of low‐performance reproducibility of perovskite TFTs. This study provides an alternative A‐cation engineering method for achieving high‐performance and reliable tin‐halide perovskite electronics.
A reliable p‐channel 2D/3D tin‐based hybrid perovskite thin‐film transistors (TFTs) comprising 3D formamidinium tin iodide (FASnI3) and 2D fluorinated 4‐fluoro‐phenethylammonium tin iodide ((4‐FPEA)2SnI4) are reported. The optimized FPEA‐incorporated TFTs show a high hole mobility of 12 cm2 V−1 s−1, an on/off current ratio of over 108, and a subthreshold swing of 0.09 V dec−1 with negligible hysteresis.
Fiber‐shaped energy storage devices have great potential for use as an intelligent power source for futuristic wearable technology. To produce high‐performance fiber‐shaped energy storage devices, a ...thin fiber material with a high energy density, shape adaptability, and longevity is critical. Herein, 3D fiber‐shaped supercapacitors (SCs) comprising MXene‐PEDOT:PSS active electrodes made using the 3D‐direct‐ink‐writing (DIW) technique are demonstrated. Embedding a silver (Ag) current collector in the active electrode facilitated faster charge transport in the fiber‐shaped 3D‐SCs, enabling them to create a unique 3D‐electrode structure that solves the thickness and length problem of electrode‐dependent capacitance in fiber‐shaped devices. At one‐meter long, the fully‐printed fiber‐shaped 3D‐SC exhibits a low charge transfer resistance that leads to the high areal capacitance of 1.062 F cm−2 and gravimetric capacitance of 185.9 F g−1, with a high areal energy density of 94.41 µWh cm−2 at a power density of 1,142 µW cm−2. The fiber‐shaped 3D‐SCs also exhibit excellent electrochemical and mechanical stability at different temperatures in air and water. With their unique electrode structure and uninterrupted power supply, these R2R 3D‐DIW printed fiber‐shaped SCs can boost the development of innovative textile technology.
This work demonstrates the fabrication of a high‐performance fiber‐shaped 3D supercapacitor using the R2R 3D‐printing process. The trade‐off between capacitance and the fiber electrode's thickness and length is successfully resolved by the novel MAM 3D electrodes, resulting in a single one‐meter fiber‐shaped 3D‐SC that shows an areal capacitance (Ca) of 1.062 F cm−2, gravimetric capacitance (Cg) of 185.9 F g−1, and a high energy density of 94.41 µWh cm−2.
