MXenes, a new family of two-dimensional structures, have recently gained significant attention due to their unique physical properties suitable for a wide range of potential applications. Here we introduce TiCT delaminated monolayers as ultrathin transparent conductors with properties exceeding comparable reduced graphene oxide films. Solution processed TiCT films exhibit sheet resistances as low as 437 Ω sq with 77% transmittance at 550 nm. Field effect transistor measurements confirm that these films have a metallic nature, which makes them suitable as electrodes. We show using Kelvin Probe Atomic Force Microscopy that the work function of delaminated TiCT flakes (with OH terminal groups) is 5.28 ± 0.03 eV. These results demonstrate that solution-processed TiCT conducting films could open up a new direction for the next generation of transparent conductive electrodes.

The emerging molybdenum disulfide (MoS ) offers intriguing possibilities for realizing a transformative new catalyst for driving the hydrogen evolution reaction (HER). However, the trade-off between catalytic activity and long-term stability represents a formidable challenge and has not been extensively addressed. This study reports that metastable and temperature-sensitive chemically exfoliated MoS (ce-MoS ) can be made into electrochemically stable (5000 cycles), and thermally robust (300 °C) while maintaining synthetic scalability and excellent catalytic activity through physical-transformation into 3D structurally deformed nanostructures. The dimensional transition enabled by a high throughput electrohydrodynamic process provides highly accessible, and electrochemically active surface area and facilitates efficient transport across various interfaces. Meanwhile, the hierarchically strained morphology is found to improve electronic coupling between active sites and current collecting substrates without the need for selective engineering the electronically heterogeneous interfaces. Specifically, the synergistic combination of high strain load stemmed from capillarity-induced-self-crumpling and sulfur (S) vacancies intrinsic to chemical exfoliation enables simultaneous modulation of active site density and intrinsic HER activity regardless of continuous operation or elevated temperature. These results provide new insights into how catalytic activity, electrochemical-, and thermal stability can be concurrently enhanced through the physical transformation that is reminiscent of nature, in which properties of biological materials emerge from evolved dimensional transitions.

UPCommonsPortal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Abstract: We studied the performance over time of opaque and semi-transparent PTB7:PC71BM bulk hetero-junction solar cells. For unsealed inverted configuration cells we observe that when the isolation from the environment is improved, the degradation observed is dominated by one single exponential decay. We demonstrate that a dielectric multilayer stack of approximately 550 nm provides an isolation that increases the lifetime of the cell close to ten times. In that event the fill factor appears to be the PV parameter dominating cell degradation resulting from a decrease in the shunt resistance. An Impedance analysis we performed indicates that a Warburg element, attributed to the presence of slowly moving charges such as heavy ions, must be included in thedescription of the experimental data. The contribution from such element increases as the cell degrades in good agreement with a degradation dominated by the corrosive effects from external agents reaching the active layer of the device. We have revised our manuscript according to the comments and suggestions from both reviewers. Enclosed with the manuscript we provide a detailed response to the reviewers points. Essentially, we do not have any strong disagreement with the reviewers remarks and we used their comments and suggestions to improve the manuscript. In response to the request of an ISOS-L-1 test made by reviewer#3, we provide a supplementary data file which is cited in the revised main text. With the submission we provide a detailed response to the reviewers points and an indication of the changes introduced. Additionally, we provide a copy of the text where all changes introduced are in blue.We would like to use this opportunity to thank you again for all the time and consideration dedicated to our manuscript. In the first paragraph in page 6 of the revised manuscript the following sentenceis included: For V< 0,6 V the Warburg feature is not observed and therefore R w is set to 0. The second paragraph in page 6 has been rewritten as follows: Nyquist plots at four different voltages are shown in figures 6 as examples of impedance measurements for three different times. We observe a good agreement between the experimental data and the theoretical fit. The main feature in the complex plane is a typical depressed semicircle in the medium-high frequency range, a standard behaviour in organic solar cells associated to carrier recombination. The semicircle diameter increases with time, which implies an increase of the parallel resistance R P . This leads to a corresponding rise of the recombination time and therefore to an enhancement of the carrier density. Besides, the semicircle depression is more pronounced with time, leading to a decrease of CPE P parameter, and thus moving away from the ideal capacitor behaviour. At low frequencies, for V = 0.6 and 0.8 V, one may observe a tail associated to a Warburg behaviour that is more pronounced as time evolves. This results in an ...

Electron acceptor degradation of organic solar cells is considered a main contributor to performance instability and a barrier for the commercialization of organic solar cells. Here, we selectively remove the electron acceptors on the surface of donor:acceptor blend films using a tape stripping technique. The near-edge X-ray absorption fine structure (NEXAFS) spectrum reveals that only 6% of the acceptor component is left on the blend film surface after the tape stripping, creating a polymer-rich surface. The optimized morphology avoids direct contact of electron acceptors with the oxygen and water molecules from the film surface. Moreover, the polymer-rich surface dramatically enhances the adhesion between the photoactive layer and the top metal electrode, which prevents delamination of the electrode. Our results finally demonstrate that the selective removal of electron acceptors near the top electrode facilitates the realization of highly durable organic solar cells that can even function under water without encapsulation.

We propose the use of whispering gallery mode coupling in a novel configuration based on implementing a thin film cell on the backside of an array of parallel fibers. We performed numerical calculations using the parameters of a thin film organic cell which demonstrate that light coupling becomes more effective as the angle for the incident light relative to the fiber array normal increases up to an optimal angle close to 55 deg. At this angle the power conversion efficiency of the fiber array solar cell we propose becomes 30% times larger than the one from an equivalent planar cell configuration. We demonstrate that the micro fiber array solar cell we propose may perform an effective partial tracking of the sun movement for over 100 degrees without any mechanical help. In addition, in the event that such fiber array cell would be installed with the adequate orientation on a vertical façade, an optimal photon-to-charge conversion would be reached for sunlight incident at 55 deg with respect to the horizon line, very close to the yearly average position for the sun at Latitude of 40 deg.