Dehumidification is a critical energy-intensive and crucial process for several industries (e.g., air conditioning and gas dehydration). Polymeric membranes with high water vapor permeability and selectivity are needed to achieve an energy-efficient water vapor removal. Herein, we demonstrate high-performance water vapor transport membranes based on novel amphiphilic tercopolymers. A series of amphiphilic tercopolymers comprising polyacrylonitrile, poly(ethylene glycol) methyl ether methacrylate (PEGMA), and poly(N,N-dimethylamino ethyl methacrylate) (PDMAEMA) segments are synthesized via an economical and facile free radical polymerization. The water vapor permeability increases with the increase in PEGMA chain length and the content of PEGMA segments. The best performing membrane (i.e., PEGMA-9502) achieved a water vapor permeability of 174 kBarrer. By optimizing the content and chain length of the PEGMA segments, the membranes could be tuned for carbon capture applications. The optimized membranes tested for CO2 separation showed a high CO2 permeability of 47 Barrer along with CO2/N2 and CO2/CH4 selectivities of 67 and 23, respectively. This work presents a simple and economic amphiphilic tercopolymer for the fabrication of membranes with excellent gas and water vapor separation performance.

A new method to synthesize an electron-rich building block cyclopentadithienothiophene (9H-thieno-[3,2-b]thieno[2″,3″:4′,5′]thieno[2′,3′:3,4]cyclopenta[1,2-d]thiophene, CDTT) via a facile aromatic extension strategy is reported. By combining CDTT with 1,1-dicyanomethylene-3-indanone endgroups, a promising nonfullerene small molecule acceptor (CDTTIC) is prepared. As-cast, single-junction nonfullerene organic solar cells based on PFBDB-T: CDTTIC blends exhibit very high short-circuit currents up to 26.2 mA cm−2 in combination with power conversion efficiencies over 11% without any additional processing treatments. The high photocurrent results from the near-infrared absorption of the CDTTIC acceptor and the well-intermixed blend morphology of polymer donor PFBDB-T and CDTTIC. This work demonstrates a useful fused ring extension strategy and promising solar cell results, indicating the great potential of the CDTT derivatives as electron-rich building blocks for constructing high-performance small molecule acceptors in organic solar cells.

Wide bandgap semiconductor (WBGS)-based deep UV (DUV) devices lag behind those operating in the visible and IR range, as no stable p-type WBGS that operates in the DUV region (<300 nm) presently exists. Here, solution-processed p-type manganese oxide WBGS quantum dots (MnO QDs) are explored. Highly crystalline MnO QDs are synthesized via femtosecond-laser ablation in liquid. The p-type nature of these QDs is demonstrated by Kelvin probe and field effect transistor measurements, along with density functional theory calculations. As proof of concept, a high-performance, self-powered, and solar-blind Schottky DUV photodetector based on such QDs is fabricated, which is capable of detecting under ambient conditions. The carrier collection efficiency is enhanced by asymmetric electrode structure, leading to high responsivity. This novel p-type MnO QD material can lead to cost-effective industrial production of high-performance solution-processed DUV optoelectronics for large-scale applications.

A multi-scale approach is employed to design metal-organic frameworks (MOFs). The methane sorption properties are studied by grand canonical Monte Carlo simulations to reveal the structure-property relationship with respect to the methane total uptake and working capacity at different temperatures and pressures. We identify rhr-MOFs with outstanding gravimetric working capacity. For example, the BBB MOF (largest studied pore size) achieves a value of 60.7 wt% at 298 K and 5–65 bar.

Contact resistance is renowned for its unfavorable impact on transistor performance. Despite its notoriety, the nature of contact resistance in organic electrochemical transistors (OECTs) remains unclear. Here, by investigating the role of contact resistance in n-type OECTs, the first demonstration of source/drain-electrode surface modification for achieving state-of-the-art n-type OECTs is reported. Specifically, thiol-based self-assembled monolayers (SAMs), 4-methylbenzenethiol (MBT) and pentafluorobenzenethiol (PFBT), are used to investigate contact resistance in n-type accumulation-mode OECTs made from the hydrophilic copolymer P-90, where the deliberate functionalization of the gold source/drain electrodes decreases and increases the energetic mismatch at the electrode/semiconductor interface, respectively. Although MBT treatment is found to increase the transconductance three-fold, contact resistance is not found to be the dominant factor governing OECT performance. Additional morphology and surface energy investigations show that increased performance comes from SAM-enhanced source/drain electrode surface energy, which improves wetting, semiconductor/metal interface quality, and semiconductor morphology at the electrode and channel. Overall, contact resistance in n-type OECTs is investigated, whilst identifying source/drain electrode treatment as a useful device engineering strategy for achieving state of the art n-type OECTs.

Organic photovoltaic power conversion efficiencies exceeding 14% can largely be attributed to the development of nonfullerene acceptors (NFAs). Many of these molecules are structural derivatives of IDTBR and ITIC, two common NFAs. By modifying the chemical structure of the acceptor, the optical absorption, energy levels, and bulk heterojunction morphology can be tuned. However, the effect of structural modifications on NFA charge transport properties has not yet been fully explored. In this work, the relationship between chemical structure, molecular packing, and charge transport, as measured in organic thin-film transistors (OTFTs), is investigated for two high performance NFAs, namely O-IDTBR and ITIC, along with their structural derivatives EH-IDTBR and ITIC-Th. O-IDTBR exhibits a higher n-type saturation field effect mobility of 0.12 cm2 V−1 s−1 compared with the other acceptors investigated. This can be attributed to the linear side chains of O-IDTBR which direct an interdigitated columnar packing motif. The study provides insight into the transport properties and molecular packing of NFAs, thereby contributing to understanding the relationship between chemical structure, material properties, and device performance for these materials. The high electron mobility achieved by O-IDTBR also suggests its applications can be extended to use as an n-type semiconductor in OTFTs.

Ternary organic solar cells (OSCs) are among the best-performing organic photovoltaic devices to date, largely due to the recent development of nonfullerene acceptors. However, fullerene molecules still play an important role in ternary OSC systems, since, for reasons not well understood, they often improve the device performance, despite their lack of absorption. Here, the photophysics of a prototypical ternary small-molecule OSC blend composed of the donor DR3, the nonfullerene acceptor ICC6, and the fullerene derivative PC71BM is studied by ultrafast spectroscopy. Surprisingly, it is found that after excitation of PC71BM, ultrafast singlet energy transfer to ICC6 competes efficiently with charge transfer. Subsequently, singlets on ICC6 undergo hole transfer to DR3, resulting in free charge generation. Interestingly, PC71BM improves indirectly the electron mobility of the ternary blend, while electrons reside predominantly in ICC6 domains as indicated by fast spectroscopy. The improved mobility facilitates charge carrier extraction, in turn leading to higher device efficiencies of the ternary compared to binary solar cells. Using the (photo)physical parameters obtained from (transient) spectroscopy and charge transport measurements, the device's current–voltage characteristics are simulated and it is demonstrated that the parameters accurately reproduce the experimentally measured device performance.

Molecular orientation and π–π stacking of nonfullerene acceptors (NFAs) determine its domain size and purity in bulk-heterojunction blends with a polymer donor. Two novel NFAs featuring an indacenobis(dithieno[3,2-b:2ʹ,3ʹ-d]pyrrol) core with meta- or para-alkoxyphenyl sidechains are designed and denoted as m-INPOIC or p-INPOIC, respectively. The impact of the alkoxyl group positioning on molecular orientation and photovoltaic performance of NFAs is revealed through a comparison study with the counterpart (INPIC-4F) bearing para-alkylphenyl sidechains. With inward constriction toward the conjugated backbone, m-INPOIC presents predominant face-on orientation to promote charge transport. The as-cast organic solar cells (OSCs) by blending m-INPOIC and PBDB-T as active layers exhibit a power conversion efficiency (PCE) of 12.1%. By introducing PC71BM as the solid processing-aid, the ternary OSCs are further optimized to deliver an impressive PCE of 14.0%, which is among the highest PCEs for as-cast single-junction OSCs reported in literature to date. More attractively, PBDB-T:m-INPOIC:PC71BM based OSCs exhibit over 11% PCEs even with an active layer thickness over 300 nm. And the devices can retain over 95% of PCE after storage for 20 days. The outstanding tolerance to film thickness and outstanding stability of the as-cast devices make m-INPOIC a promising candidate NFA for large-scale solution-processable OSCs.

We report a strong effect of the MXene flake size and surface termination on the dielectric permittivity of MXene polymer composites. Specifically, poly(vinylidene fluoride-trifluoro-ethylene-chlorofluoroehylene) or P(VDF-TrFE-CFE) polymer embedded with large (ca. 4.5 μm) Ti3C2Tx flakes achieves a dielectric permittivity as high as 105 near the percolation limit of 15.3 wt % MXene loading. In comparison, the dielectric permittivity of MXene/P(VDF-TrFE-CFE) using small (ca. 1.5 μm) Ti3C2Tx flakes (S-MXene) achieves a dielectric permittivity of 104 near the percolation limit of 16.8 wt %. Meanwhile, increasing the concentration of surface functional groups on the MXene surface (−O, −F, and −OH) by extending the etching time gives a dielectric constant of 2204 near the percolation limit of 15.7 wt %. The ratio of permittivity to the loss factor of our large flake composite is superior to that of the small flake composite, and to all previously reported carbon-based fillers in P(VDF-TrFE-CFE). We show that the dielectric permittivity enhancement is strongly related to the charge accumulation at the surfaces between the two dimensional (2D) MXene flakes and the polymer matrix under an external applied electric field.

The astonishing recent progress in the field of metal oxide thin-film transistors (TFTs) and their debut in commercial displays is accomplished using vacuum-processed multicomponent oxide semiconductors. However, emulating this success with their solution-processable counterparts poses numerous scientific challenges. Here, the development of high mobility n-channel TFTs based on ultrathin (<10 nm) alternating layers of In2O3 and ZnO that are sequentially deposited to form heterojunction and superlattice channels is reported. The resulting TFTs exhibit high electron saturation mobility (13 cm2 V−1 s−1), excellent current on/off ratios (>108) with nearly zero onset voltages and hysteresis-free operation despite the low temperature processing (≤200 °C). The enhanced performance is attributed to the formation of a quasi-2D electron gas-like system at the In2O3/ZnO heterointerface due to the conduction band offset. It is shown that altering the oxide deposition sequence has an adverse effect on electron transport due to formation of trap states. Optimized multilayer TFTs are shown to exhibit improved bias-stress stability compared to single-layer TFTs. Modulating the electron concentration within the superlattice channel via selective n-doping of the ZnO interlayers leads to almost 100% saturation mobility increase (≈25 cm2 V−1 s−1) even when the TFTs are fabricated on flexible plastic substrates.