John P. Murphy

Hybrid organic–inorganic perovskite composite fibers produced via melt electrospinning

A novel fabrication technique for producing hybrid organic–inorganic perovskite impregnated poly(styrene) microfibers in situ in a melt electrospinner is presented. The relationship between the hybrid perovskite precursors, electrospun fiber morphology, and chemical phase domains was investigated using light microscopy, scanning electron microscopy, x-ray diffraction spectroscopy, and energy dispersive spectroscopy. The method was successful in producing composite microfibers and revealed information regarding the nature of encapsulated hybrid perovskites under higher-than-normal temperature conditions during the synthesis and subsequent annealing process.

Coaxial hybrid perovskite fibers: Synthesis and encapsulation in situ via electrospinning

In this study, a new method for producing fibers with hybrid organic–inorganic perovskite (HOIP) cores and hydrophobic polystyrene shells via coaxial electrospinning is introduced. The presence of the HOIP, CH3NH3PbI3, was verified through the use of ultraviolet to visible spectroscopy and x-ray diffractography to confirm successful synthesis in situ. Morphologies of the coaxial fibers were investigated using scanning electron microscopy to confirm the core/shell geometry and assess the fiber diameter. Finally, the interaction of liquid water and the fiber mats was studied to assess improvements to moisture resistance garnered from encapsulation in coaxial electrospun fibers.

Lithography via electrospun fibers with quantitative morphology analysis

Electrospun fibers have been used to enhance material properties, as drug delivery devices, and for physical filtration systems. However, the use of electrospinning as a viable method for lithographic patterning and subsequent pattern transfer has not been demonstrated. As with traditional lithography methods, feature position and size are critical to the performance and repeatability of resultant structures. The placement of electrospun fibers is driven by the electrostatic field strength. In the present research, the electrostatic field strength between the spinneret (capillary) and the substrate (collection electrode) is controlled by modifying the voltage applied to two electrodes on or adjacent to the substrate. Such manipulation modifies the applied electrostatic field, creating a stronger field strength directed at one electrode as compared to the other. The fiber will preferentially be directed to the electrode along the path of highest field strength, resulting in deposition to the desired electr...

Electrospun charge transport structures for hybrid perovskite solar cells

Hybrid perovskite solar cells are rapidly climbing in efficiency and are close to large-scale commercialization due to continued efforts in improving the opto-electronic properties and stability of hybrid perovskite materials. Improvements to the charge transport structures in hybrid perovskite solar cells allow for much higher charge extraction from perovskite solar cells, improving overall efficiency of solar cells utilizing electrospun charge transport structures. Electrospinning and postprocessing techniques were utilized to produce high surface area electron and hole transport structures for use in perovskite solar cells, and opto-electronic properties and surface/layer interactions were studied.Hybrid perovskite solar cells are rapidly climbing in efficiency and are close to large-scale commercialization due to continued efforts in improving the opto-electronic properties and stability of hybrid perovskite materials. Improvements to the charge transport structures in hybrid perovskite solar cells allow for much higher charge extraction from perovskite solar cells, improving overall efficiency of solar cells utilizing electrospun charge transport structures. Electrospinning and postprocessing techniques were utilized to produce high surface area electron and hole transport structures for use in perovskite solar cells, and opto-electronic properties and surface/layer interactions were studied.

Electrospinning for nano- to mesoscale photonic structures

Abstract The fabrication of photonic and electronic structures and devices has directed the manufacturing industry for the last 50 years. Currently, the majority of small-scale photonic devices are created by traditional microfabrication techniques that create features by processes such as lithography and electron or ion beam direct writing. Microfabrication techniques are often expensive and slow. In contrast, the use of electrospinning (ES) in the fabrication of micro- and nano-scale devices for the manipulation of photons and electrons provides a relatively simple and economic viable alternative. ES involves the delivery of a polymer solution to a capillary held at a high voltage relative to the fiber deposition surface. Electrostatic force developed between the collection plate and the polymer promotes fiber deposition onto the collection plate. Issues with ES fabrication exist primarily due to an instability region that exists between the capillary and collection plate and is characterized by chaotic motion of the depositing polymer fiber. Material limitations to ES also exist; not all polymers of interest are amenable to the ES process due to process dependencies on molecular weight and chain entanglement or incompatibility with other polymers and overall process compatibility. Passive and active electronic and photonic fibers fabricated through the ES have great potential for use in light generation and collection in optical and electronic structures/devices. ES produces fiber devices that can be combined with inorganic, metallic, biological, or organic materials for novel device design. Synergistic material selection and post-processing techniques are also utilized for broad-ranging applications of organic nanofibers that span from biological to electronic, photovoltaic, or photonic. As the ability to electrospin optically and/or electronically active materials in a controlled manner continues to improve, the complexity and diversity of devices fabricated from this process can be expected to grow rapidly and provide an alternative to traditional resource-intensive fabrication techniques.

Using Electric Field Manipulation to Fabricate Nanoscale Fibers On Large Areas: A Path to Electronic and Photonic Devices.

Traditional fabrication methods for the integrated circuit (IC) and the microelectromechanical systems (MEMS) industries have been developed primarily for two-dimensional fabrication on planar surfaces. More recently, commercial electronics are expeditiously emerging with non-planar displays and rapid prototype machines can be purchased for the price of a modern laptop. While electrospinning (ES) has been in existence for over 100 years, this fabrication method has not been adequately developed for commercial fabrication of electronics or the rapid prototyping industries. ES provides many benefits as a fabrication method including tunability of fiber size and affordable hardware. To realize the full potential of ES as a commonplace fabrication method for modern devices, precise control, real-time fiber morphology monitoring, and the creation of a comprehensive databank of accurate models for prediction is essential. The aim of this research is to accomplish these goals through several avenues. To improve fiber deposition control, both passive and active methods are employed to modify electric field lines during the ES process. COMSOL models have been developed to meticulously mimic experimental results for predictive planning, and an in situ laser diagnostic tool was developed to measure real-time fiber morphology during electrospinning. Further, post-processing data was generated through the use of two-dimensional fast Fourier transform (2D-FFT) to monitor alignment, and four-point conductivity measurements were taken via four independently-positioned micromanipulator probes. This article describes the devices developed to date, the a priori modeling approach taken, and resultant capabilities which complement ES as an attractive fabrication method for the electronic and photonic industry.