Gamma Knife Radiosurgery for Mesial Temporal Lobe Epilepsy

Many patients with mesial temporal lobe epilepsy continue to have seizures despite medical therapy. For these patients, one recourse is surgical resection of the mesial temporal lobe, with its attendant risks. Noninvasive treatment with Gamma Knife radiosurgery is under active investigation as a possible alternative to open surgery. Accumulated evidence from multiple studies shows radiosurgery to be comparable in outcomes to surgical resection. A definitive randomized, controlled trial, the Radiosurgery or Open Surgery for Epilepsy (ROSE) trial, is currently underway, and further investigation of this promising treatment is crucial in our advancement of alternative therapies to treat refractory epilepsy

Cross-Linkable, Solvent-Resistant Fullerene Contacts for Robust and Efficient Perovskite Solar Cells with Increased <i>J</i>_SC and <i>V</i>_OC

The active layers of perovskite solar cells are also structural layers and are central to ensuring that the structural integrity of the device is maintained over its operational lifetime. Our work evaluating the fracture energies of conventional and inverted solution-processed MAPbI₃ perovskite solar cells has revealed that the MAPbI₃ perovskite exhibits a fracture resistance of only ∼0.5 J/m², while solar cells containing fullerene electron transport layers fracture at even lower values, below ∼0.25 J/m². To address this weakness, a novel styrene-functionalized fullerene derivative, <b>MPMIC</b>_<b>60</b>, has been developed as a replacement for the fragile PC₆₁BM and C₆₀ transport layers. <b>MPMIC</b>_<b>60</b> can be transformed into a solvent-resistant material through curing at 250 °C. As-deposited films of <b>MPMIC</b>_<b>60</b> exhibit a marked 10-fold enhancement in fracture resistance over PC₆₁BM and a 14-fold enhancement over C₆₀. Conventional-geometry perovskite solar cells utilizing cured films of <b>MPMIC</b>_<b>60</b> showed a significant, 205% improvement in fracture resistance while exhibiting only a 7% drop in PCE (13.8% vs 14.8% PCE) in comparison to the C₆₀ control, enabling larger <i>V</i>_OC and <i>J</i>_SC values. Inverted cells fabricated with <b>MPMIC</b>_<b>60</b> exhibited a 438% improvement in fracture resistance with only a 6% reduction in PCE (12.3% vs 13.1%) in comparison to those utilizing PC₆₁BM, again producing a higher <i>J</i>_SC

High Performance Roll-to-Roll Produced Fullerene-Free Organic Photovoltaic Devices via Temperature-Controlled Slot Die Coating

Solution-processed organic photovoltaics (OPVs) have continued to show their potential as a low-cost power generation technology; however, there has been a significant gap between device efficiencies fabricated with lab-scale techniques—i.e., spin coating—and scalable deposition methods. Herein, temperature-controlled slot die deposition is developed for the photoactive layer of OPVs. The influence of solution and substrate temperatures on photoactive films and their effects on power conversion efficiency (PCE) in slot die coated OPVs using a 3D printer-based slot die coater are studied on the basis of device performance, molecular structure, film morphology, and carrier transport behavior. These studies clearly demonstrate that both substrate and solution temperatures during slot die coating can influence device performance, and the combination of hot substrate (120 °C) and hot solution (90 °C) conditions result in mechanically robust films with PCE values up to 10.0% using this scalable deposition method in air. The efficiency is close to that of state-of-the-art devices fabricated by spin coating. The deposition condition is translated to roll-to-roll processing without further modification and results in flexible OPVs with PCE values above 7%. The results underscore the promising potential of temperature-controlled slot die coating for roll-to-roll manufacturing of high performance OPVs. © 2018 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim1

Additive Engineering:A Route Towards Flexible and Robust Perovskite Solar Cells

The record performance reached by metal halide perovskite in solar cells in a very short time calls for a real word application, however, several major intrinsic limitations need to be solved before the technological maturation can be reached. The intrinsic instability, the poor control of perovskite materials' properties deposited via wet processing, and the intrinsic mechanical fragility of the polycrystalline films are the among the most relevant issue. Herein, the use of polymeric additive has been investigated as a mean to gaining a control over the processing and improving the perovskite material stability to the environmental factors, eventually to developing perovskite inks compatible with large area solar cells manufacturing. Several polymers were evaluated based on their solubility and compatibility with perovskite precursors solutions. Among all, starch polysaccharide has been selected since it can induce a convenient viscosity modulation that make perovskite precursors' inks with different printing techniques. Importantly, starch can also enhance perovskite materials mechanical strength and tolerance to thermal stress.</p

Beyond Fullerenes: Indacenodithiophene-Based Organic Charge-Transport Layer toward Upscaling of Low-Cost Perovskite Solar Cells

Phenyl-C₆₁-butyric acid methyl ester (PCBM) is universally used as the electron-transport layer (ETL) in the low-cost inverted planar structure of perovskite solar cells (PeSCs). PCBM brings tremendous challenges in upscaling of PeSCs using industry-relevant methods due to its aggregation behavior, which undermines the power conversion efficiency and stability. Herein, we highlight these, seldom reported, challenges with PCBM. Furthermore, we investigate the potential of nonfullerene indacenodithiophene (IDT)-based molecules by employing a commercially available variant, 3,9-bis­(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis­(4-hexylphenyl)-dithieno­[2,3-<i>d</i>:2′,3′-<i>d</i>′]-<i>s</i>-indaceno­[1,2-<i>b</i>:5,6-<i>b</i>′] dithiophene (ITIC), as a PCBM replacement in ambient-processed PeSCs. Films fabrication by laboratory-based spin-coating and industry-relevant slot-die coating methods are compared. Although similar power-conversion efficiencies are achieved with both types of ETL in a simple device structure fabricated by spin-coating, the nanofibriller morphology of ITIC compared to the aggregated morphology of PCBM films enables improved mechanical integrity and stability of ITIC devices. Upon slot-die coating, the aggregation of PCBM is exacerbated, leading to significantly lower power-conversion efficiency of devices than spin-coated PCBM as well as slot-die-coated ITIC devices. Our results clearly indicate that IDT-based molecules have great potential as an ETL in PeSCs, offering superior properties and upscaling compatibility than PCBM. Thus, we present a short summary of recently emerged nonfullerene IDT-based molecules from the field of organic solar cells and discuss their scope in PeSCs as electron or hole-transport layer

Effect of cation composition on the mechanical stability of perovskite solar cells

Photoactive perovskite semiconductors are highly tunable, with numerous inorganic and organic cations readily incorporated to modify optoelectronic properties. However, despite the importance of device reliability and long service lifetimes, the effects of various cations on the mechanical properties of perovskites are largely overlooked. In this study, the cohesion energy of perovskites containing various cation combinations of methylammonium, formamidinium, cesium, butylammonium, and 5-aminovaleric acid is reported. A trade-off is observed between the mechanical integrity and the efficiency of perovskite devices. High efficiency devices exhibit decreased cohesion, which is attributed to reduced grain sizes with the inclusion of additional cations and PbI2 additives. Microindentation hardness testing is performed to estimate the fracture toughness of single-crystal perovskite, and the results indicated perovskites are inherently fragile, even in the absence of grain boundaries and defects. The devices found to have the highest fracture energies are perovskites infiltrated into a porous TiO2/ZrO2/C triple layer, which provide extrinsic reinforcement and shielding for enhanced mechanical and chemical stability

23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability

As the record single-junction efficiencies of perovskite solar cells now rival those of copper indium gallium selenide, cadmium telluride and multicrystalline silicon, they are becoming increasingly attractive for use in tandem solar cells due to their wide, tunable bandgap and solution processability. Previously, perovskite/silicon tandems were limited by significant parasitic absorption and poor environmental stability. Here, we improve the efficiency of monolithic, two-terminal, 1-cm2perovskite/silicon tandems to 23.6% by combining an infrared-tuned silicon heterojunction bottom cell with the recently developed caesium formamidinium lead halide perovskite. This more-stable perovskite tolerates deposition of a tin oxide buffer layer via atomic layer deposition that prevents shunts, has negligible parasitic absorption, and allows for the sputter deposition of a transparent top electrode. Furthermore, the window layer doubles as a diffusion barrier, increasing the thermal and environmental stability to enable perovskite devices that withstand a 1,000-hour damp heat test at 85 °C and 85% relative humidity