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We report an environmentally friendly resistive switching memory device on a biodegradable Ecoflex elastomeric substrate using nontoxic and disintegrable polyfluorene/poly(butylene succinate) (PFN/...

Tin perovskite solar cells (TPSCs) are rising as the most promising candidates for lead-free PSCs. However, the randomly crystallized tin halide perovskite with a high concentration of defects is still the bottleneck for obtaining high efficiency. Here, we report the pretreatment of FASnI3 (formamidinium, FA) perovskite film by spin-coating a solution of organic halide salt n-propylammonium iodide (PAI) before annealing. It is found that PAI can induce the templated growth of FASnI3 crystals by reconstruction of the intermediate phase, resulting in a highly crystallized FASnI3 film with preferential orientation along the (100) plane and suppressed trap density. Finally, a stabilized efficiency of 11.22% was certified at an accredited test center and the cell is stable, maintaining over 95% of its initial efficiency after 1000 hours of operation at the maximum power point.

The appealing advantage of using an electrospinning technique to improve the elastomeric properties of conjugated polymers is demonstrated in this study. It is revealed that the electrospinning process can strengthen the low-crystalline feature of the prepared nanofibers. By combining the use of a polymer with low glass transition temperature, extremely stretchable nanofibers can be successfully prepared. P-type poly(3-hexylthiophene-2,5-diyl) (P3HT) electrospun (ES) nanofibers show a low Young's modulus of 0.448 GPa and still exhibit a high hole mobility of >10−2 cm2 V−1 s−1 even under an external strain of 500%. Based on these prepared P3HT ES nanofibers, a fully stretchable field-effect transistor (FET) and photomemory are realized. Besides, stretchable n-type poly{[N,N′-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (N2200) ES nanofibers are also successfully prepared with strain tolerance up to 400% strain, showing the general applicability of our proposed method.

The rapid emergency of data science, information technology, and artificial intelligence (AI) relies on massive data processing with high computing efficiency and low power consumption. However, the current von‐Neumann architecture system requires high‐energy budget to process data computing and storage between central computing unit and memory. To overcome this problem, neuromorphic computing system which mimics the operation of human brain has been proposed to perform computing in an energy‐efficient manner. Recently, organic–inorganic halide perovskite compounds have been demonstrated as promising components for neuromorphic devices owing to their strong light absorption, solution processability, and unique properties such as ion migration, carrier trapping effects and phase transition. In this review paper, we report recent advances of neuromorphic devices which employed organic–inorganic halide perovskite compounds by analyzing their fundamental operating mechanisms, device architectures, applications and future prospective.

We report the fabrication and optical/mechanical properties of perovskite/thermoplastic polyurethane (TPU)-based multicolor luminescent core-shell nanofibers and their large-scale fiber mats. One-step coaxial perovskite/TPU nanofibers had a high photoluminescence quantum yield value exceeding 23.3%, surpassing that of its uniaxial counterpart, due to the homogeneous distribution of perovskite nanoparticles (NPs) by the confinement of the TPU shell. The fabricated core-shell nanofibers exhibited a high mechanical endurance owing to the well elastic properties of TPU and maintained the luminescence intensity even under a 100% stretched state after 1000 stretching-relaxing cycles. By taking advantage of the hydrophobic nature of TPU, the ambient and moisture stability of the fabricated fibers were enhanced up to 1 month. Besides, large-area stretchable nanofibers with a dimension of 15 cm × 30 cm exhibiting various visible-light emission peaks were fabricated by changing the composition of perovskite NPs. Moreover, a large-scale luminescent and stretchable fiber mat was successfully fabricated by electrospinning. Furthermore, the white-light emission from the fabricated fibers and mats was achieved by incorporating orange-light-emitting poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] into the TPU shell and coupling the turquoise blue-light-emitting perovskite NPs in the core site. Finally, the integrity of the perovskite-based TPU fibers was realized by fabricating a light-emitting diode (LED) device containing the orange-light-emitting fibers embedded in the polyfluorene emissive layer. This work demonstrated an effective way to prepare stable and stretchable luminous nanofibers and the integration of such nanofibers into LED devices, which could facilitate the future development of wearable electronic devices.

Inspired by the low energy consumption, high parallel and fault‐tolerance of visual perception system in human brain, optoelectronic devices integrated with the sensing, memory, and signal processing functionalities become the candidate to emulate functions of photonic synapse. Herein, red‐light‐stimulated nonvolatile perovskite‐based photomemory through optimized thickness of poly(3‐hexylthiophene‐2,5‐diyl)(P3HT) is demonstrated. The device emulates important synaptic functions which can be manipulated by light intensity, light pulse interval, and number of presynaptic spikes. The lower photon energy triggered photonic device paves the way for developing low energy consumption of neuromorphic computing in the future.

The rapid development of wearable electronic devices has prompted a strong demand to develop stretchable organic solar cells (OSCs) to serve as the advanced powering systems. However, to realize an intrinsically stretchable OSC is challenging because it requires all the constituent layers to possess certain elastic properties. It thus necessitates a combined engineering of charge-transporting layers and photoactive materials. Herein, we first describe a stretchable electron-extraction layer using a blend of poly[(9,9-bis(3'-( N, N-dimethylamino)propyl)-2,7-fluorene)- alt-2,7-(9,9-dioctylfluorene)] (PFN) and nitrile butadiene rubber (NBR, Nipol 1072). This hybrid PFN/NBR layer exhibits a much lower Derjaguin-Muller-Toporov modulus (0.45 GPa) than the value (1.25 GPa) of the pristine PFN and could withstand a high strain (60% strain) without showing any cracks. Moreover, besides enriching the stretchability of PFN, the terminal carboxyl groups of NBR can ionize PFN to promote its solution-processability in polar solvents and to ensure the interfacial dipole formation at the corresponding interface in the device, as evidenced by the Fourier transform infrared and ultraviolet photoelectron spectroscopy analyses. By further coupling the replacement of [6,6]-phenyl-C

In recent years, the exploitation of stretchable organic solar cell (OSC) has attracted significant research interests due to the rapid progress of wearable electronics. However, the development of a stretchable OSC is quite challenging since it has a strict requirement for the mechanical deformability and durability of each constituent layer in device. In this work, we successfully fabricated an efficient, stretchable inverted OSC by adopting a buckle-on-elastomer strategy, for which an ultrathin poly(ethylene naphthalate) (PEN) substrate coupled with a pre-strained (100%) 3M elastomeric tape was employed as the device substrate. Owing to the pre-strained status of the elastomer, the ensemble wrinkle will be formed in response to accommodate the strain once the pre-strain was released, which can afford the derived OSC with a much improved mechanically robustness and stretchability. As a result, we demonstrated that a pristine efficient (PCE: 5.61%) OSC using such buckling scaffold can remain its 74% efficiency under 30% compression and, more importantly, can still retain its 64.3% efficiency after 50-cycle compression-stretching testing from 0% to 30% compression. Besides, the effects of mechanical deformation and durability on the electrical performance are also investigated. This work proves that the buckle-on-elastomer strategy can be a good solution for realizing efficient OSCs with reasonably good mechanical durability, revealing great potential serving as an ultrathin and lightweight power source for wearable device applications.

We report the synthesis, morphology, and photophysical properties of new conjugated rod-coil block copolymers consisting of poly[2,7-(9,9-dihexylfluorene)] (PF) conjugated rods and soft poly(n-butyl acrylate) (PBA) coils for stretchable light-emitting device applications. The PF-b-PBA thin films could form obvious self-assembled nanofibrillar structures after the solvent annealing treatment. Besides this, both the deformability and optical properties of block copolymers were controllable by varying the PF/PBA ratio. The annealed PF4k-b-PBA7k thin film exhibited pure blue emission with a high photoluminescence quantum yield of over 22.5% under 100% strain, validating the excellent stretchability and promising stability. Furthermore, a stretchable and fluorescent PF-b-PBA based microporous template with tunable regularity can be fabricated through the breath figure method. These results demonstrated that the novel intrinsically deformable and luminescent rod-coil block copolymers could have versatile applications in stretchable light-emitting devices.

Tin oxide (SnO2) has recently attracted significant research interest for its role functioning as an efficient electron-transporting layer (ETL) due to its higher charge mobility than the commonly used titanium oxide (TiO2) for realizing high-performance perovskite solar cells (PVSCs). However, it is still challenging to develop a facile, low-temperature solution-based (

To address the challenges of reliability and facile processability of a benchmark polymer PTB7-Th, one of the most prevailing donor materials utilized in organic solar cells, we have systematically investigated the correlations among chemical structure, processing, morphology and device performance. Our study reveals that the regioregularity of PTB7-Th plays a crucial role in polymer properties as well as the fabrication process of devices. The regioregular polymer entirely consisting of favourable repeat units is capable of realizing high power conversion efficiency (>10%) in organic solar cells without using any solvent additive and tedious processing treatments. More importantly, the device efficiency based on this regioregular polymer is insensitive over a broad range of film thickness (from 100 nm to >400 nm). This will be very advantageous for manufacturing highly efficient and stable polymer solar cells by high throughput fabrication processes.

Organic–inorganic hybrid perovskite solar cells (PVSC) have appeared as promising high power-per-weight power systems for wearable electronic devices. Herein, we utilized a low-temperature electrodeposited tin oxide (SnO2) electron-transporting layer (ETL) coupled with a thin PCBM ETL and a functional encapsulating layer to realize an efficient, stable textile-based flexible PVSC. We first demonstrated that an easily accessible elastomer can serve as an effective encapsulating material for the fabricated flexible PVSC, as exemplified by the largely improved ambient stability and waterproof properties. Furthermore, we established that the good adhesive properties generated by the elastomer can largely enrich the deployable capability of the completed device stack as evidenced by the effortless integration of a completed device stack onto a textile. As a result, a ∼15% textile-based flexible PVSC with improved ambient stability and washable capability was demonstrated. A proof-of-concept device was successfully integrated with other electronic devices on a unitary textile to serve as an efficient power supply system for wearable electronic devices. The findings revealed in this work can promote the future potential applications of PVSCs in wearable device applications.

This chapter provides the readers a brief overview of the building blocks in the chemical structures of organic semiconductors and fabrication and characterization in organic field-effect transistors (OFET) devices and to provide their flexible electronic applications. Typical OFETs consist of four main components: active organic semiconducting layer, gate dielectric (insulator), three terminals (gate, source, and drain contact), and supporting substrate. The chapter presents the study of the major developments in OFET structures and operation principles, and discusses the characteristic parameters of OFETs for analyzing device performance. It analyses several first-generation p-type and n-type molecular and polymeric semiconductors used in the active layer. The performance of OFETs is characterized in terms of the important parameters, including the field-effect mobility, threshold voltage, ON/OFF ratio, and subthreshold swing. The selection of substrate materials for the device mainly relies on the different kinds of applications.

A one-step core/shell electrospinning technique is exploited to fabricate uniform luminous perovskite-based nanofibers, wherein the perovskite and the polymer are respectively employed in the core and the outer shell. Such a coaxial electrospinning technique enables the in situ formation of perovskite nanocrystals, exempting the needs of presynthesis of perovskite quantum dots or post-treatments. It is demonstrated that not only the luminous electrospun nanofibers can possess color-tunability by simply tuning the perovskite composition, but also the grain size of the formed perovskite nanocrystals is largely affected by the perovskite precursor stoichiometry and the polymer solution concentration. Consequently, the optimized perovskite electrospun nanofiber yields a high photoluminescence quantum yield of 30.9%, significantly surpassing the value of its thin-film counterpart. Moreover, owing to the hydrophobic characteristic of shell polymer, the prepared perovskite nanofiber is endowed with a high resistance to air and water. Its photoluminescence intensity remains constant while stored under ambient environment with a relative humidity of 85% over a month and retains intensity higher than 50% of its initial intensity while immersed in water for 48 h. More intriguingly, a white light-emitting perovskite-based nanofiber is successfully fabricated by pairing the orange light-emitting compositional perovskite with a blue light-emitting conjugated polymer.

A molecular nano-floating gate (NFG) of pentacene-based transistor memory devices is developed using conjugated polymer nanoparticles (CPN) as the discrete trapping sites embedded in an insulating polymer, poly (methacrylic acid) (PMAA). The nanoparticles of polyfluorene (PF) and poly(fluorene-alt-benzo[2,1,3]thiadiazole (PFBT) with average diameters of around 50–70 nm are used as charge-trapping sites, while hydrophilic PMAA serves as a matrix and a tunneling layer. By inserting PF nanoparticles as the floating gate, the transistor memory device reveals a controllable threshold voltage shift, indicating effectively electron-trapping by the PF CPN. The electron-storage capability can be further improved using the PFBT-based NFG since their lower unoccupied molecular orbital level is beneficial for stabilization of the trapped charges, leading a large memory window (35 V), retention time longer than 104 s with a high ON/OFF ratio of >104. In addition, the memory device performance using conjugated polymer nanoparticle NFG is much higher than that of the corresponding polymer blend thin films of PF/polystyrene. It suggests that the discrete polymer nanoparticles can be effectively covered by the tunneling layer, PMAA, to achieve the superior memory characteristics.

We fabricated dual functional electrospun (ES) nanofibers by a coaxial electrospinning technique for enhancing the organic photovoltaic (OPV) device efficiency. The nanofibers contained poly[2,7-(9,9-dihexylfluorene)-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT) nanoparticles as the luminescent solar concentrator (LSC) and Ag nanoparticles for the surface plasmon resonance (SPR) effect. Aligned- and crossed-fiber architecture patterns were fabricated to compare the effects of the architecture on the OPV efficiency. The plasmonic-enhanced LSC ES nanofibers with crosslinked poly(methacrylic acid) could be directly integrated into the conventional OPV configuration without sacrificing the coverage area of the active layer. In addition, the in situ reduction of Ag nanoparticles simultaneously enhanced the exciton generation of PFBT and the active materials with the SPR effect. The dual functional ES nanofibers with a crossed-pattern embedded into OPV devices provided significant light harvesting through down conversion and enhanced exciton generation. They led to PCE values of 4.11 and 7.12% for P3HT (poly(3-hexylthiophene)) : PC61BM ([6,6]-phenyl C61-butyric acid methyl ester) and PTB7 (polythieno[3,4-b]-thiophene-co-benzodithiophene) : PC71BM ([6,6]-phenyl C71-butyric acid methyl ester) ([6,6]-phenyl) photovoltaic cells, respectively, which are 18% enhancements compared to their parent devices. This interface-modification approach using plasmonic-enhanced LSC ES nanofibers provides a new approach for enhancing the OPV device performance.

Solution-processable organic-inorganic hybrid perovskite materials with a wealth of exotic semiconducting properties have appeared as the promising front-runners for next-generation electronic devices. Further, regarding its well photoresponsibility, various perovskite-based photosensing devices are prosperously developed in recent years. However, most exploited devices to date only transiently transduce the optical signals into electrical circuits while under illumination, which necessitates using additional converters to further store the output signals for recording the occurrence of light stimulation. Herein, a nonvolatile perovskite-based floating-gate photomemory with a multilevel memory behavior is demonstrated, for which a floating gate comprising a polymer matrix impregnated with perovskite nanoparticles is employed. Owing to the well photoresponsibility introduced by the embedded nanoparticles, the device is enabled to access multiple wavelength response and the functionalities of recording power/time-dependent illumination under no vertical electrical field. Intriguingly, a nonvolatility of photorecording exceeding three months with a high On/Off current ratio over 104 can be achieved.

We prepared aligned poly(3-hexylthiophene) (P3HT) nanofibers for the application of organic field-effect transistor (OFET) by two-fluid coaxial electrospinning (ES) technique using P3HT as core and PMMA as shell, followed by extraction of PMMA. Effects of shell flow rate and thermal annealing temperature on the morphology and optoelectronic properties were explored. The experimental results showed that the prepared P3HT nanofibers were highly aligned and their diameters were smaller in the case of low shell flow rate. The OFET carrier mobility of aligned P3HT ES nanofibers using the low shell flow rate could be dramatically improved up to 3 orders of magnitude (1.92 × 10−1 cm2/V·s with the on/off ratio of 4.45 × 104) in comparison with those from the high shell flow rate. The results of wide-angle X-ray scattering (WAXS) and photophysical properties (optical absorption and polarized photoluminescence) suggested the enhancement of π−π stacking and crystallinity of P3HT in the nanofibers at a lower shell fl...

Rigid fused perylene diimide (PDI) dimers bridged with heterocycles exhibit superior photovoltaic performance compared to their unfused semiflexible analogues. Changing the chalcogen atoms in the aromatic bridges gradually increases the twist angles between the two PDI planes, leading to a varied morphology in which the one bridged by thiophene achieves a balance and shows the best efficiency of 6.72%.

This study describes the first perovskite-based redox resistive switching memory using CH3NH3PbBr3 nanoparticles (NPs) dispersed in an insulating solid polymer electrolyte, poly(ethylene oxide) (PEO), and scrutinizes it in detail. Herein, PEO is chosen not only to perform a matrix function due to its ionic conductivity but also to support a preservative material surrounding the CH3NH3PbBr3 NPs to improve their stability. Further, it is revealed that PEO can serve as the chelating agent to coordinate with PbBr2/CH3NH3PbBr3 NPs in consequence of the direct interaction between Pb2+ cations and electron pairs of ether oxygen on the PEO chain to provide a host medium for the Pb2+ cations on both amorphous and crystalline phases. Consequently, it facilitates the associated redox-based reactions to result in the metallic filament formation in the derived device, leading to the write-once-read-many times resistive switching behavior. The field-effect scanning electron microscopy and X-ray photoelectron spectroscopy analyses are conducted to ascertain the detailed mechanism. It is unveiled that a stable dendritic-like filament is grown in the CH3NH3PbBr3 NPs:PEO hybrid film, which is thus proposed to be the origin of the stable low resistive state and recovery of the conductive path during the reverse bias scan. This study presents a new perspective on the perovskite-based resistive memory devices.

An extra electric fi eld is introduced below the spinneret in an electrospinning setup for producing poly(3-hexylthiophene) (P3HT) nanofi bers. The liquid jet is greatly prolonged by the additional extensional force and thinner fi bers can thus be obtained. The chain conformation and orientation in fiare probed by differential scanning calorimetry and X-ray diffraction techniques. Under the infl uence of the secondary electric fi eld, P3HT chains are extensively stretched and aligned along the fi ber axis. The electrospun P3HT nanofi bers are fabricated into fi eld-effect transistors and the charge carrier mobilities of the nanofi bers with and without secondary electric fi eld are found to be 1.54 × 10 −4 and 1.62 × 10 −1 cm 2 V −1 s −1 , respectively. The dramatic enhancement of mobility by more than 1000 times is due to the effective charge transport through the delocalization of electrons along the highly extended and oriented P3HT backbones rather than the ordinary π‐π stacking. In addition to P3HT, it is found that this simple method also works for poly(3-alkylthiophene).

Measurements of magnetic circular dichroism in Fe $2p$ resonant photoemission and calculations based on a full-multiplet cluster model reveal the parameters of the electronic structure of ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}.$ We obtained on-site Coulomb energy ${U}_{\mathrm{dd}}$ of $3d$ electrons, charge-transfer energy $\ensuremath{\Delta}$ which is defined as the energy required to transfer an electron from O $2p$ to Fe $3d,$ and the hybridization strength between Fe $3d$ and O $2p$ at different Fe ion sites of ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ by analyzing the data of magnetic circular dichroism. The charge-transfer energy of ${\mathrm{Fe}}^{3+}$ ions was found to be significantly smaller than that of ${\mathrm{Fe}}^{2+}$ ions. We determined the energy positions of the low-lying multiplets of each Fe ion site. These energy positions for ${\mathrm{Fe}}^{3+}$ ion sites are 1.5\char21{}2.5 eV higher than those obtained from band-structure calculations. Our calculations also show that the photoemission spectral weight in binding energy bigger than 10 eV is substantial, in contrast to the results of band-structure calculations. Our findings conclude that ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ is a system with strong electron-electron interactions.

Significant enhancement of P3HT (poly(3-hexylthiophene)):PC61BM ([6,6]-phenyl C61-butyric acid methyl ester) photovoltaic devices using different patterns of electrospun Ag/PVP composite nanofibers, including nonwoven, aligned, and crossed patterns, is reported. The composite electrospun nanofibers are prepared using in situ reduction of silver (Ag) nanoparticles in Ag/poly(vinyl pyrrolidone) (PVP) via a two-fluid coaxial electrospinning technique. The composition, crystalline orientation, and particle size of Ag are manipulated by controlling the core/shell solution concentration. The smallest diameter of the composite nanofibers leads to the highest orientation of the Ag nanoparticles and results in the largest conductivity due to geometric confinement. Such composite nanofibers exhibit the surface plasmon resonance (SPR) effect, which provides near field enhancement of electromagnetic field around active layer. Additionally, composite nanofibers with the crossed or nonwoven patterns further enhance high carrier mobility, compared to that of the aligned pattern. It leads to the 18.7% enhancement of the power conversion efficiency of photovoltaic cell compared to the parent device. The results indicate that the high conductivity and SPR effect of the Ag/PVP electrospun nanofibers can significantly improve the photocurrent and PCE, leading to promising organic solar cell applications.