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Abstract Halide perovskite solar cells (PSCs) are a state-of-the-art photovoltaic technology that exhibit high efficiencies and can be manufactured using roll-to-roll systems. However, PSCs are currently fabricated using sequential layer-by-layer deposition, which constrains the selection of suitable functional layers in the solar cell and limits the processing conditions and techniques that can be used. Lamination via diffusion bonding is a scalable parallel-processing technique that has the capability to overcome some of the challenges of sequential deposition by widening the thermal processing window and reducing the chemical compatibility requirements for PSC manufacturing. However, there remains a lack of detailed understanding of the process-structure-property relationships needed to accelerate the development of high-volume lamination-based manufacturing processes. In this work, we introduce a method to study the process-structure-property relationships of laminated perovskite semiconductors by using a custom photoluminescence (PL) spectroscopy system to quantify spatial heterogeneity in laminated halide perovskite (HP) materials. PL is an important figure-of-merit used to quantify the optoelectronic properties of semiconductor materials used in PV manufacturing. The spatial variation in PL of a laminated HP film is compared to that of an unlaminated HP film. The PL system uses servomotors and an Arduino microcontroller to automate a PL mapping procedure. The PL equipment is tunable to achieve a minimum possible spot size of ∼50 μm, enabling high-resolution measurements. The system is used to measure the PL of 19 separate locations on both a laminated and unlaminated HP material. The results of this study reveal that lamination at optimal conditions will improve the average PL peak intensity of the HP by 55%, indicating that lamination has the potential to improve the optoelectronic characteristics of PSCs. However, lamination also increases the standard deviation of PL peak intensity. Therefore, although lamination improves the PL of HPs, it also induces unwanted spatial heterogeneity. This warrants future studies on the governing physical mechanisms that determine quality control metrics in lamination-based PSC manufacturing. 

Electrotactile stimulus is a form of sensory substitution in which an electrical signal is perceived as a mechanical sensation. The electrotactile effect could, in principle, recapitulate a range of tactile experience by selective activation of nerve endings. However, the method has been plagued by inconsistency, galvanic reactions, pain and desensitization, and unwanted stimulation of nontactile nerves. Here, we describe how a soft conductive block copolymer, a stretchable layout, and concentric electrodes, along with psychophysical thresholding, can circumvent these shortcomings. These purpose-designed materials, device layouts, and calibration techniques make it possible to generate accurate and reproducible sensations across a cohort of 10 human participants and to do so at ultralow currents (≥6 microamperes) without pain or desensitization. This material, form factor, and psychophysical approach could be useful for haptic devices and as a tool for activation of the peripheral nervous system. 

Understanding the role of ferroelectric polarization in modulating the electronic and structural properties of crystals is critical for advancing these materials for overcoming various technological and scientific challenges. However, due to difficulties in performing experimental methods with the required resolution, or in interpreting the results of methods therein, the nanoscale morphology and response of these surfaces to external electric fields has not been properly elaborated. In this work we investigate the effect of ferroelectric polarization and local distortions in a BaTiO 3 perovskite, using two widely used computational approaches which treat the many-body nature of X-ray excitations using different philosophies, namely the many-body, delta-self-consistent-field determinant (mb-ΔSCF) and the Bethe–Salpeter equation (BSE) approaches. We show that in agreement with our experiments, both approaches consistently predict higher excitations of the main peak in the O–K edge for the surface with upward polarization. However, the mb-ΔSCF approach mostly fails to capture the L 2,3 separations at the Ti–L edge, due to the absence of spin–orbit coupling in Kohn–Sham density functional theory (KS-DFT) at the generalized gradient approximation level. On the other hand, and most promising, we show that application of the GW/BSE approach successfully reproduces the experimental XAS, both the relative peak intensities as well as the L 2,3 separations at the Ti–L edges upon ferroelectric switching. Thus simulated XAS is shown to be a powerful method for capturing the nanoscale structure of complex materials, and we underscore the need for many-body perturbation approaches, with explicit consideration of core-hole and multiplet effects, for capturing the essential physics in these systems. 

Abstract Understanding the optoelectronic properties of optically active materials at the nanoscale often proves challenging due to the diffraction-limited resolution of visible light probes and the dose sensitivity of many optically active materials to high-energy electron probes. In this study, we demonstrate correlative synchrotron-based scanning x-ray excited optical luminescence (XEOL) and x-ray fluorescence (XRF) to simultaneously probe local composition and optoelectronic properties of halide perovskite thin films of interest for photovoltaic and optoelectronic devices. We find that perovskite XEOL stability, emission redshifting, and peak broadening under hard x-ray irradiation correlates with trends seen in photoluminescence measurements under continuous visible light laser irradiation. The XEOL stability is sufficient under the intense x-ray probe irradiation to permit proof-of-concept correlative mapping. Typical synchrotron XRF and nano-diffraction measurements use acquisition times 10–100 x shorter than the 5-second acquisition employed for XEOL scans in this study, suggesting that improving luminescence detection should allow correlative XEOL measurements to be performed successfully with minimal material degradation. Analysis of the XEOL emission from the quartz substrate beneath the perovskite reveals its promise for use as a real-time in-situ x-ray dosimeter, which could provide quantitative metrics for future optimization of XEOL data collection for perovskites and other beam-sensitive materials. Overall, the data suggest that XEOL represents a promising route towards improved resolution in the characterization of nanoscale heterogeneities and defects in optically active materials that may be implemented into x-ray nanoprobes to complement existing x-ray modalities.