Organic Dye Molecule Intercalated Vanadium Oxygen Hydrate Enables High-Performance Aqueous Zinc-Ion Storage

Although the layered vanadium oxide-based materials have been considered to be one of the candidates for aqueous Zn-ion batteries (AZIBs), it still faces inevitable challenges of unsatisfactory capacities and sluggish kinetics because of strong electrostatic interactions between Zn-ions and structure lattice. This work addresses the strategy of pre-inserting guest materials to vanadium oxide cathode using different intercalants. To achieve this goal, the small organic dye molecules, methyl orange (MO), and methylene blue (MB) are proposed as the intercalants for vanadium oxygen hydrate (VOH). It has been demonstrated that use of these intercalants can facilitate reaction kinetics between Zn2+ and VOH, leading to an improvement of specific capacity (293 mAh g-1 at 0.3 A g-1 for MO-VOH and 311 mAh g-1 for MB-VOH) compared to VOH, a large enhancement of excellent energy density (237.1 Wh kg-1 for MO-VOH, 232.3 Wh kg-1 for MB-VOH), and a prolong lifespan operation at 3 A g-1 . The mechanism studies suggest that the weakened electrostatic interactions between the Zn-ions and V-O lattice after intercalating organic molecules contribute to boosting the electrochemical performance of AZIBs unveiled by charge density difference and binding energy.

Facile Approach to Preparing a Vanadium Oxide Hydrate Layer as a Hole-Transport Layer for High-Performance Polymer Solar Cells

We demonstrate a facile and green approach to preparing a vanadium oxide hydrate (VO_x·nH₂O) layer to serve as the hole-transport layer (HTL) in high-performance polymer solar cells (PSCs). The VO_x·nH₂O layer was in situ prepared by a combined H₂O₂ and ultraviolet-ozone (UVO) processing on a VO_x layer. The as-prepared VO_x·nH₂O layer featured a work function of 5.0 ± 0.1 eV, high transmittance, and better interface properties compared to those of the generally prepared VO_x (UVO or thermal annealing) layers. PSCs based on poly[(ethylhexyl-thiophenyl)-benzodithiophene-(ethylhexyl)-thienothiophene]/[6,6]-phenyl-C₇₁-butyric acid methyl ester using the VO_x·nH₂O layer as the HTL yielded high power conversion efficiencies (PCEs) up to 8.11%, outperforming the devices with VO_x layers (PCE of 6.79% for the UVO-processed VO_x layer and 6.10% for the thermally annealed VO_x layer) and conventional polyethylenedioxythiophene-polystyrenesulfonate (PEDOT:PSS) layers (PCE of 7.67%). The improved PCE was attributed to the enhanced J_SC and/or fill factor, which mainly correlate to the improved interfacial contact between the photoactive layer and the indium tin oxide/HTL or cathode when using the VO_x·nH₂O layer as the HTL. A similar improvement in the PCE was also observed for the PSCs based on poly(3-hexylthiophene)/[6,6]-phenyl-C₆₁-butyric acid methyl ester. In addition, PSCs with a VO_x·nH₂O layer as the HTL showed a higher stability than that of those with a PEDOT:PSS layer. Hence, it would be possible to use this simply and in situ prepared VO_x·nH₂O layer as an inexpensive HTL for high-performance PSCs.