The Synthesis of a Multiple D-A Conjugated Macrocycle and Its Application in Organic Photovoltaic

As a novel class of materials, D-A conjugated macrocycles hold significant promise for chemical science. However, their potential in photovoltaic remains largely untapped due to the complexity of introducing multiple donor and acceptor moieties into the design and synthesis of cyclic π-conjugated molecules. Here, we report a multiple D-A ring-like conjugated molecule (RCM) via the coupling of dimer molecule DBTP-C3 as a template and thiophenes in high yields. RCM exhibits a narrow optical gap (1.33 eV) and excellent thermal stability, and shows a remarkable photoluminescence yield (ΦPL ) of 11.1 % in solution, much higher than non-cyclic analogues. Organic solar cell (OSC) constructed with RCM as electron acceptor shows efficient charge separation at donor-acceptor band offsets and achieves a power conversion efficiency (PCE) of 14.2 %-approximately fourfold higher than macrocycle-based OSCs reported so far. This is partly due to low non-radiative voltage loss down to 0.20 eV and a high electroluminescence yield (ΦEL ) of 4×10-4 . Our findings emphasize the potential of D-A cyclic conjugated molecules in advancing organic photovoltaic technology.

Transport layer engineering towards lower threshold for perovskite lasers

Charge transport layers are essential for achieving electrically pumped perovskite lasers. However, their role in perovskite lasing is not fully understood. Here, we explore the role of charge transport layers on the lasing actions of perovskite films by investigating the amplified spontaneous emission (ASE) thresholds. We demonstrate a largely reduced ASE threshold and enhanced ASE intensity by introducing an additional hole transport layer poly(triaryl amine) (PTAA). We show that the key role of the PTAA layer is to accelerate the hot carrier cooling process by extracting holes in perovskites. With reduced hot holes, the Auger recombination loss is largely suppressed, resulting in decreased ASE threshold. Our argument is further supported by the fact that the ASE threshold can be further reduced from 25.7 to 7.2 μJ/cm² upon switching the pumping wavelength from 400 nm to 500 nm to directly avoid excess hot hole generation. Our work for the first time exemplifies how to further reduce the ASE threshold with transport layer engineering through hot hole manipulation. This is critical to maintaining the excellent gain properties of perovskites when integrating them into electrical devices, paving the way for electrically pumped perovskite lasers. This article is protected by copyright. All rights reserved.

Nonfullerene-Based Organic Photodetectors for Ultrahigh Sensitivity Visible Light Detection

It is well established that for organic photodetectors (OPDs) to compete with their inorganic counterparts, low dark currents at reverse bias must be achieved. Here, two rhodanine-terminated nonfullerene acceptors O-FBR and O-IDTBR are shown to deliver low dark currents at -2 V of 0.17 and 0.84 nA cm^-2, respectively, when combined with the synthetically scalable polymer PTQ10 in OPD. These low dark currents contribute to the excellent sensitivity to low light of the detectors, reaching values of 0.57 μW cm^-2 for PTQ10:O-FBR-based OPD and 2.12 μW cm^-2 for PTQ10:O-IDTBR-based OPD. In both cases, this sensitivity exceeds that of a commercially available silicon photodiode. The responsivity of the PTQ10:O-FBR-based OPD of 0.34 AW^-1 under a reverse bias of -2 V also exceeds that of a silicon photodiode. Meanwhile, the responsivity of the PTQ10:O-IDTBR of 0.03 AW^-1 is limited by the energetic offset of the blend. The OPDs deliver high specific detectivities of 9.6 × 10¹² Jones and 3.3 × 10¹¹ Jones for O-FBR- and O-IDTBR-based blends, respectively. Both active layers are blade-coated in air, making them suitable for high-throughput methods. Finally, all three of the materials can be synthesized at low cost and on a large scale, making these blends good candidates for commercial OPD applications.

Bone mineral and lean tissue loss after long duration space flight

The loss of bone and muscle is a major concern for long duration space flight. In December of 1989, we established a collaboration with Russian colleagues to determine the bone and lean tissue changes in cosmonauts before and after flights on the Mir space station lasting 4-14.4 months. Eighteen crew members received a lumbar spine and hip DEXA scan (Hologic 1000W) before and after flight; 17 crew members received an additional whole body scan. All results were expressed as percent change from baseline per month of flight in order to account for the different flight times. The pre-and post-flight data were analyzed using Hotelling's T(2) for 3 groups of variables: spine, neck of femur, trochanter; whole body BMD and subregions; lean (total, legs, arms) and fat (total only). A paired t-test was used as a follow-up to the Hotelling's T(2) to identify the individual measurements that were significantly different. These data define the rate and extent of bone and lean tissue loss during long duration space flight and indicate that the current in-flight exercise program is not sufficient to completely ameliorate bone and muscle loss during weightlessness.

Muscle volume, MRI relaxation times (T2), and body composition after spaceflight

Postflight changes in muscle volume, calf muscle transverse relaxation time, and total body composition were measured in 4 crewmembers after a 17-day mission and in 14-16 crewmembers in multiple shuttle/Mir missions of 16- to 28-wk duration. During the 17-day mission, all muscle regions except the hamstrings significantly decreased 3-10% compared with baseline. During the shuttle/Mir missions, there were significant decreases in muscle volume (5-17%) in all muscle groups except the neck. These changes, which reached a new steady state by 4 mo of flight or less, were reversed within 30-60 days after landing. Postflight swelling and elevation of calf muscle transverse relaxation time persisted for several weeks after flight, which suggests possible muscle damage. In contrast to the 17-day flight, in which loss in fat, but not lean body mass, was found (25), losses in bone mineral content and lean body mass, but not fat, were seen after the longer shuttle/Mir missions. The percent losses in total body lean body mass and bone mineral content were similar at approximately 3.4-3.5%, whereas the pelvis demonstrated the largest regional bone loss at 13%.

Effect of Habit Modification on Optical and X-ray Structures of Sodium Halate Mixed Crystals: The Etiology of Anomalous Double Refraction

Structures of mixed crystals of the isomorphous salts NaClO3 and NaBrO3 (sodium chlorate and sodium bromate, respectively) were reinvestigated by X-ray diffraction. Contrary to previous reports, NaCl x Br1−x O3 is not cubic. Data from adjacent {100} growth sectors of crystals of varying composition were refined in the triclinic space group P1; halate ions occupy nominally symmetry-related sites nonstatistically. Optical measurements showed that six asymmetric sectors in cubes are disposed to give an object with approximate tetrahedral point symmetry. We address forgotten anomalies, first observed almost 150 years ago, which could have been a sufficient basis for earlier structural reinvestigations. The mixed-crystal structure speaks to the general non-applicability of the Law of Isomorphism to solid solutions. A link between optical anisotropy and nonstatistical guest site occupancy was achieved by annealing crystals between 523 and 533 K. Na2S2O3 and Na2S2O6 were used as habit-modifying impurities to produce NaCl x Brl−x O3 crystals with {111} and {\overline 1\overline 1\overline 1} habits, respectively. Diffraction data from {111} and {\overline 1\overline 1\overline 1} growth sectors were refined in the trigonal space group R3. In each case the pyramidal halate ion that was located on the special position was depleted in BrO3 −. Conoscopic optical investigations nevertheless showed that the crystals are biaxial with a small 2V (10–15°), in marked contrast to the 90° angle in {100} crystals. We failed to reconcile the optical and X-ray structures by calculating the optical indicatrix with bond polarizability sum models. This led us to estimate the magnitude of other factors which contribute to the optical properties, including strain associated with dislocations which may exert its influence through combined piezoelectric and linear electro-optic effects.

Effects of spaceflight on bone mineralization in the rhesus monkey

We combined dual-photon absorptiometry, iliac crest histomorphometry, and backscattered electrons analysis to characterize bone mineralization effects of a spaceflight on young monkeys. Two 4- to 5-kg male rhesus monkeys (Macaca mulatta) were flown during a 11.5-day spaceflight that took place onboard Cosmos 2229 biosatellite (Bion 10). Vivarium (n = 4) and Earth-based chair (n = 4) control situations were studied for comparison. Flight monkeys exhibited lower values of iliac cancellous bone volume, associated with nonsignificantly thinner trabeculae. Bone mineralization rate and the proportion of trabecular bone surface involved in mineralization processes were found markedly reduced after spaceflight. Analysis of embedded sections by backscattered electrons imaging showed a nonsignificant shift to lower mineralization in the flight biopsies vs. postflight mock-up biopsies. These results were in accordance with dual-photon absorptiometry evaluations showing a tendency for decreased bone mineral content during flight and recovery thereafter. The ground simulation experiment performed on the same monkeys more than 1 mo after landing suggests that the observed effects were specifically related to spaceflight and that the animals had only partially recovered. Additional animals on future flights will be required to confirm these findings.

Bone and body mass changes during space flight

Body mass, calcium and skeletal changes occur in humans who have worked in microgravity. Physiologic changes are seen as early as one week and are still occurring 312 days into space flight. The physiologic changes in bone and mineral metabolism may be among those which limits long duration space flight if an adequate countermeasure is not developed. The purpose of this paper is to summarize what is known about calcium dynamics and bone mineral changes as well as associated changes of body mass induced by space flight. The data reported is from a variety of studies conducted in both actual and simulated space flight.