Giant Polarization Sensitivity via the Anomalous Photovoltaic Effect in a Two-Dimensional Perovskite Ferroelectric.

Polarization sensitivity, which shows great potential in photoelectric detection, is expected to be significantly improved by the ferroelectric anomalous photovoltaic (APV) effect. However, it is challenging to explore new APV-active ferroelectrics due to severe polarization fatigue induced by the leakage current of photoexcited carriers. For the first time, we report a strong APV effect in a 2D hybrid perovskite ferroelectric assembled by alloying mixed organic cations, (HA)2(EA)2Pb3Br10 (1, where HA+ is n-hexylammonium and EA+ is ethylammonium), which has a large spontaneous polarization ∼3.8 µC/cm2 and high a Curie temperature ∼378 K. Its ferroelectricity allows a strong APV effect with an above-bandgap photovoltage up to 7.4 V, which exceeds its bandgap (∼2.7 eV). Most strikingly, based on the dependence on polarized-light angle, this strong APV effect renders the highest level of polarization sensitivity with a giant current ratio of ∼25, far beyond other 2D single-phase materials. This study sheds light on the exploration of APV-active ferroelectrics and inspires their future high-performance optoelectronic device applications.

Acquiring Bulk Anomalous Photovoltaic Effect in Single Crystals of a Lead-Free Double Perovskite with Aromatic and Alkali Mixed-Cations.

The bulk anomalous photovoltaic (BAPV) effect of acentric materials refers to a distinct concept from traditional semiconductor-based devices, of which the above-bandgap photovoltage hints at a promise for solar-energy conversion. However, it is still a challenge to exploit new BAPV-active systems due to the lacking of knowledge on the structural origin of this concept. BAPV effects in single crystals of a 2D lead-free double perovskite, (BBA)2 CsAgBiBr7 (1, BBA = 4-bromobenzylammonium), tailored by mixing aromatic and alkali cations in the confined architecture to form electric polarization are acquired here. Strikingly, BAPV effects manifested by above-bandgap photovoltage (VOC ) show unique attributes of directional anisotropy and positive dependence on electrode spacing. The driving source stems from orientations of the polar aromatic spacer and Cs+ ion drift, being different from the known built-in asymmetry photovoltaic heterojunctions. As the first demonstration of the BAPV effect in the double perovskites, the results will enrich the family of environmentally green BAPV-active candidates and further facilitate their new optoelectronic application.

Soft Multiaxial Molecular Ferroelectric Thin Films with Self-Powered Broadband Photodetection.

Molecular ferroelectric films (MFFs) offer a good platform for miniaturized electronic devices, which are inseparable from their multiaxial nature. Despite great studies, soft MFFs with broadband photo-electroactivity still remain a huge blank as the photoexcited leakage current will severely deteriorate ferroelectricity, hindering their optoelectronic applications. Here, we constructed the multiaxial MFF of HA2EA2Pb3I10 (1, where EA = ethylammonium and HA = n-hexylammonium) in 2D multilayered perovskites. Eight equivalent polarization directions were observed in 1, as verified by its symmetry breaking (i.e., 4/mmmFm species), which is the maximum among 2D multilayered perovskites and even more than that of classic ceramic BaTiO3. Specially, spin-coated flexible MFFs of 1 are approximately orientated parallel to layered perovskite frameworks, exhibiting in-plane spontaneous polarization (Ps = 1.8 µC/cm2) and broadband absorption (∼1.83 eV). In addition, self-powered broadband detection (∼0.55 µA/cm2 at 637 nm illumination) was achieved on the soft films, revealing their potential for flexible and wearable electronic devices. Our result sheds light on the design of flexible photoelectronic devices and provides an effective way to expand the applications of 2D molecular ferroelectric materials.

Broadband Photoresponses from Ultraviolet to Near-Infrared (II) Region through Light-induced Pyroelectric Effects in a Hybrid Perovskite.

Broadband photodetection has shown a great promise for diverse applications, while the realization of plateau photoresponse from ultraviolet (UV) to near-infrared (NIR) spectral region is very challenging. Herein, we exploit photoexcited pyroelectric effect in a chiral hybrid perovskite, (N, N-dimethylcyclohexylammonium)PbBr3 (1), serving as a new pathway to drive broadband photoactivities. It is a room-temperature pyroelectric with large polarization of ≈6.4 µC cm-2 and high pyroelectric figure-of-merits (FV =1.0×10-2  cm2 µC-1 and FD =7.1×10-5  Pa-1/2 ). Strikingly, light-induced pyroelectric effect arising from spontaneous polarization is observed in 1, which cover UV (266 nm) to NIR-II (1950 nm) full spectral region. The broadband photoresponses actualized by pyroelectricity break the limit of optical band gap. As the first demonstration of photo-pyroelectricity covering UV-to-NIR spectral region in hybrid perovskites, this work paves a pathway to assemble high-performance smart devices.

Iodine-mediated regioselective synthesis of vinyl triflones from styrenes with CF3SO2Na.

An unexpected regioselective synthesis of vinyl triflones was developed. This iodine-mediated C-H triflylation of styrenes with CF3SO2Na occurred at room temperature affording various vinyl triflones, which could be used for the preparation of other CF3SO2-containing compounds.

A high-temperature double perovskite molecule-based antiferroelectric with excellent anti-breakdown capacity for energy storage.

Halide double perovskites have recently emerged as an environmentally green candidate toward electronic and optoelectronic applications owing to their non-toxicity and versatile physical merits, whereas study on high-temperature antiferroelectric (AFE) with excellent anti-breakdown property remains a huge blank in this booming family. Herein, we present the first high-temperature AFE of the lead-free halide double perovskites, (CHMA)2CsAgBiBr7 (1, where CHMA+ is cyclohexylmethylammonium), by incorporating a flexible organic spacer cation. The typical double P-E hysteresis loops and J-E curves reveal its concrete high-temperature AFE behaviors, giving large polarizations of ~4.2 µC/cm2 and a high Curie temperature of 378 K. Such merits are on the highest level of molecular AFE materials. Particularly, the dynamic motional ordering of CHMA+ cation contributes to the formation of antipolar alignment and high electric breakdown field strength up to ~205 kV/cm with fatigue endurance over 104 cycles, almost outperforming the vast majority of molecule counterparts. This is the first demonstration of high-temperature AFE properties in the halide double perovskites, which will promote the exploration of new "green" candidates for anti-breakdown energy storage capacitor.

Improper High-Tc Perovskite Ferroelectric with Dielectric Bistability Enables Broadband Ultraviolet-to-Infrared Photopyroelectric Effects.

The photopyroelectric effect in ferroelectrics has shown great potential for application in infrared detection and imaging. One particular subclass is broadband with dielectric bistability, which allows for large pyroelectric figures-of-merit (FOMs). Herein, an improper high-Tc perovskite ferroelectric, (IA)2 (EA)2 Pb3 Cl10 (1, where IA is isoamylammonium and EA is ethylammonium) is presented, in which spontaneous polarization (Ps ) stems from the dynamic ordering of organic cations and the tilting of distorted PbCl6 octahedra. Notably, 1 displays unusual dielectric bistability with small variations in the temperature-dependent dielectric constants near Tc  = 392 K; this bistable attribute endows large pyroelectric FOMs with peak voltage efficiency (FV  = 1.7×10-2  cm2 µC-1 ) and sensitivity (FD  = 3.9×10-4 Pa-1/2 ). These FV and FD parameters, beyond those of their proper counterparts, make 1 a promising candidate for infrared photodetection. As expected, the broadband photopyroelectric effects observed in 1 covered the ultraviolet to infrared-II spectral region (266-1950 nm). Such Ps -directed photoactivities overcome the optical bandgap limitation and allow for wide-wave photodetection. As an innovative study on improper ferroelectricity, light is shaded here on the targeted engineering of new electrically ordered candidate materials for smart optoelectronic devices.

A molecular pyroelectric enabling broadband photo-pyroelectric effect towards self-driven wide spectral photodetection.

Broadband spectral photoresponse has shown bright prospects for various optoelectronic devices, while fulfilling high photoactivity beyond the material bandgap is a great challenge. Here, we present a molecular pyroelectric, N-isopropylbenzylaminium trifluoroacetate (N-IBATFA), of which the broadband photo-pyroelectric effects allow for self-driven wide spectral photodetection. As a simple organic binary salt, N-IBATFA possesses a large polarization (~9.5 µC cm-2), high pyroelectric coefficient (~6.9 µC cm-2 K-1) and figures-of-merits (FV = 187.9 × 10-2 cm2 µC-1; FD = 881.5 × 10-5 Pa-0.5) comparable to the state-of-art pyroelectric materials. Particularly, such intriguing attributes endow broadband photo-pyroelectric effect, namely, transient currents covering ultraviolet (UV, 266 nm) to near-infrared (NIR, 1950 nm) spectral regime, which breaks the restriction of its optical absorption and thus allows wide UV-NIR spectral photodetection. Our finding highlights the potential of molecular system as high-performance candidates toward self-powered wide spectral photodetection.

2D Hybrid perovskite incorporating cage-confined secondary ammonium cations toward effective photodetection.

By confining the secondary dimethylammonium (DMA) cation in a distorted perovskite cavity, we assembled a new 2D Ruddlesden-Popper metal halide perovskite of (i-BA)2(DMA)Pb2Br7 (i-BA = n-isobutylammonium), in which the DMA cation templates its inorganic perovskite framework and the quantum-well motif renders a fascinating photoresponse. Crystal-based planar arrays exhibit effective photodetection behaviors, including a notable detectivity (∼5.6 × 1012 Jones), a high responsivity (∼1.25 A W-1) and a large switching ratio (∼1.5 × 103). These properties result from its low dark current restricted to the hopping barrier of the insulated organic bilayer and a strong in-plane photoresponse correlated with the perovskite network. This work throws light on the targeted exploration of photosensitive candidates in the family of organic-inorganic hybrid perovskites, as well as high-performance devices.

Record high-Tc and large practical utilization level of electric polarization in metal-free molecular antiferroelectric solid solutions.

Metal-free antiferroelectric materials are holding a promise for energy storage application, owing to their unique merits of wearability, environmental friendliness, and structure tunability. Despite receiving great interests, metal-free antiferroelectrics are quite limited and it is a challenge to acquire new soft antiferroelectric candidates. Here, we have successfully exploited binary CMBrxI1-x and CMBrxCl1-x solid solution as single crystals (0 ≤ x ≤ 1, where CM is cyclohexylmethylammonium). A molecule-level modification can effectively enhance Curie temperature. Emphatically, the binary CM-chloride salt shows the highest antiferroelectric-to-paraelectric Curie temperature of ~453 K among the known molecular antiferroelectrics. Its characteristic double electrical hysteresis loops provide a large electric polarization up to ~11.4 µC/cm2, which endows notable energy storage behaviors. To our best knowledge, this work provides an effective solid-solution methodology to the targeted design of new metal-free antiferroelectric candidates toward biocompatible energy storage devices.

Correlation between computed tomography volumetry and nuclear medicine split renal function in live kidney donation: a single-centre experience.

BACKGROUND: Potential live renal donors undergo both renal computed tomography angiogram (CTA) and nuclear imaging dimercaptosuccinic acid (DMSA) scans. Each kidney's renal function and vascular anatomy influences the choice of donor side. Although DMSA measures differential blood flow, it is a surrogate for renal function and nephron mass. Computed tomography techniques can provide volumetry information. The aim of this study was to determine the relationship between measured split renal volumes on computed tomography versus renal volumes derived from DMSA split function in live donors. METHODS: Prospective data of live kidney donors assessed at a single Australian centre from 2014 to 2017 were reviewed. All patients had pre-operative CTA and DMSA imaging. Renal volume was determined via semi-automated software calculation from CTA three-dimensional image reconstructions by one investigator. Measured split renal volume was compared against calculated renal volume using measured DMSA split function (percentage split function multiplied by total renal volume). RESULTS: Fifty-three patients were included in the study. Split renal volumes on three-dimensional CTA images correlate to calculated split volumes determined from DMSA (Pearson coefficient 0.95 for right renal volume, 0.95 for left). The decision of which kidney to remove can be achieved with CTA only. Omitting a DMSA scan would reduce the radiation load by 0.70 mSv (35 chest X-rays) and potential cost saving of AU$1062.00 per donor. CONCLUSION: CTA technology allows accurate assessment of renal volumes that correlate well with DMSA split function. Avoiding a DMSA scan results in cost and radiation reduction in the assessment of a live kidney donor.

The impact of intra-operative cell salvage during open nephrectomy.

OBJECTIVE: To assess the impact of intra-operative cell salvage on outcomes in open nephrectomy. METHODS: A retrospective cohort study was performed of all patients undergoing open nephrectomy for suspected malignancy from 1 October 2013 to 1 October 2017. Patients were grouped and compared based on whether they received intra-operative cell salvage (ICS). Primary outcomes were allogeneic transfusion rates (ATRs), and if histology confirmed cancer, disease recurrence. Secondary outcomes were complications and transfusion-related cost. RESULTS: Forty patients underwent open nephrectomy for suspected malignancy during the enrolment period. Sixteen patients received ICS while 24 did not (standard group). Compared with the standard group, ICS patients had similar median age (63.5 vs. 61.0 years; p = 0.83) but fewer females (19% vs. 58%; p = 0.013). The groups were similar in pre-operative and discharge haemoglobin, Charlson Comorbidity Index, length of hospital stay and proportion with thoracoabdominal surgical approach. The ICS group had a smaller proportion undergoing partial nephrectomy (19% vs. 54%; p = 0.025) and shorter median follow-up (278 vs. 827 days; p = 0.0005). Histology was malignant for 14 ICS and 15 standard patients. The ICS group had more frequent ≥T2 disease (79% vs. 27%; p = 0.005). There were no positive margins. Both groups had similar ATRs (6% vs. 4%; p = 0.96), complication rates (19% vs. 29%; p = 0.46) and recurrence rates (18% vs. 7%; p = 0.40). Transfusion costs were higher amongst ICS patients (AUD $878.18 vs. $49.65 per patient). CONCLUSION: ICS appears safe, with low rates of recurrence and complication. Both groups had low ATRs, and therefore cost benefit for ICS was not seen.

The impact of intra-operative cell salvage during open radical prostatectomy.

BACKGROUND: To examine the effect of intra-operative cell salvage (ICS) in open radical prostatectomy. METHODS: In this retrospective cohort study, all patients undergoing open radical prostatectomy for malignancy at our institution between 10/04/2013 and 10/04/2017 were enrolled. Patients were grouped and compared based on whether they received ICS. Primary outcomes were allogeneic transfusion rates, and disease recurrence. Secondary outcomes were complications and transfusion-related cost. RESULTS: Fifty-nine men were enrolled; 30 used no blood conservation technique, while 29 employed ICS. There were no significant differences between groups in age, pre- or post-operative haemoglobin, Charlson comorbidity index, operation duration or length of stay. Tumour characteristics were also similar between groups, including pre-operative prostate specific antigen, post-operative Gleason score, T-stage, nodal status and rates of margin positivity. Compared with controls, the ICS group had longer follow up (945 vs. 989 days; P=0.0016). The control and ICS groups were not significantly different in rates of tumour recurrence (6 vs. 3 patients; P=0.30) or complications (10 vs. 5 patients; P=0.16). While the proportion of patients receiving allogenic transfusion was similar (9 vs. 6 patients; P=0.41), fewer red blood products transfused (40 vs. 12 units) meant transfusion related costs were lower in ICS patients (AUD $47,666 vs. $37,429). CONCLUSIONS: ICS reduced transfusion related costs, without affecting allogeneic transfusion rates, tumour recurrence or complication rates. These findings extend the literature supporting ICS in oncological surgery. Prospective randomised studies are needed to confirm the existing level III evidence.