Tuning Hole Transport Properties and Perovskite Crystallization via Pyridine-Based Molecules for Quasi-2D Perovskite Solar Cells.

Quasi-2D perovskites show great potential as photovoltaic devices with superior stability, but the power conversion efficiency (PCE) is limited by poor carrier transport. Here, it is simultaneously affected the hole transport layer (HTL) and the perovskite layer by incorporating pyridine-based materials into poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) to address the key problem above in 2D perovskites. With this approach, the enhanced optoelectronic performance of the novel PEDOT:PSS is due to electron transfer between the additives and PEDOT or PSS, as well as a dissociation between PEDOT and PSS based on experimental and theoretical studies, which facilitates the charge extraction and transfer. Concurrently, in-situ X-ray scattering studies reveal that the introduction of pyridine-based molecules alters the transformation process of the perovskite intermediate phase, which leads to a preferred orientation and ordered distribution caused by the Pb─N chemical bridge, achieving efficient charge transport. As a result, the pyridine-treated devices achieve an increased short-circuit current density (Jsc) and PCE of over 17%.

In Situ Growth 3D GDY-NCNTs Nanocomposites for High-Performance Supercapacitors.

New binary carbon composites (GDY-NCNTs and GDY-CNTs) with a three-dimensional porous structure, which are synthesized by an in situ growth method, are adopted in this article. The GDY-NCNTs composites exhibit excellent specific capacitance performance (679 F g-1, 2 mV s-1, 139% increase compared to GDY-CNTs) and good cycling stability (with a capacity retention rate of up to 116% after 10000 cycles). The three-dimensional porous structure not only promotes ion transfer and increases the effective specific surface area to improve its specific capacitance performance but also adapts to the volume expansion and contraction during the charging and discharging process to improve its cycling stability. The presence of nitrogen doping in the carbon nanotubes of GDY-NCNTs increases the surface defects of the composites, provides more electrochemical points, and improves the surface wettability of the composites, further improving the electrochemical performance of the composites.

Electrochemical Anion-Exchanged synthesis of porous Ni/Co hydroxide nanosheets for Ultrahigh-Capacitance supercapacitors.

The commonly reported calcination strategy usually requires high temperature to crack the metal-organic frameworks (MOFs) particles, which often lead to uncontrollable growth of nanomaterials. Here, for the first time, we utilize an electrochemical anion-exchanged method to control the hydrolysis of MOFs and synthesize porous Ni/Co hydroxide nanosheets. After the electrochemical anion-exchange, the organic ligands of MOFs nanosheets can be recycled and reused. Applying an electric field to the MOFs bulk in alkaline solution can accelerate the nucleation rate of hydroxide and change the migration behavior of charged ions/molecules, which can tailor the microstructure of derivatives and improve deep charge and discharge capability of the electrodes. As a result, the hydroxide with the optimized Ni:Co molar ratio of 7:3 and electric-field application time of 1000 cycles [Ni0.7Co0.3(OH)2-1000c] provides much better electrochemical properties than the materials synthesized without electric-field assistance: a high specific capacitance of 2115C g-1 (4230F g-1). A hybrid supercapacitor with the Ni0.7Co0.3(OH)2-1000c electrode shows a high energy density of 74.7 Wh kg-1, an improved power density (5,990.6 W kg-1), and an excellent cyclic stability (8,000 cycles). This study not only provides a novel strategy for the preparation of low-cost, deep-discharge electrodes for supercapacitors, but also proposes an unconventional method for mild synthesizing MOFs materials into porous nanoscale derivatives with tailored micromorphology.

A three-dimensional conductive cross-linked all-carbon network hybrid as a sulfur host for high performance lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries, as one of the most promising energy storage devices, have attracted widespread attentions due to their high theoretical energy density and environmental friendliness. However, the commercialized application of Li-S batteries is still restricted by several problems, including the dissolution of polysulfides in electrolyte and low conductivity of sulfur. Herein, a three-dimensional conductive cross-linked all-carbon network as a host matrix of sulfur is rationally designed and constructed using biomass silkworm faeces derived porous carbon (SFPC), reduction graphene oxide (rGO) and carbon nanotubes (CNTs) via a one-pot heat treatment approach. Meanwhile, it is found that the amounts of rGO and CNTs added have a great influence on the electrochemical properties of electrode. The optimum contents of CNTs and GO were explored, which are both 5% (the as-prepared material denoted as 55-PGC@SFPC). The obtained 55-PGC@SFPC/S with high content sulfur of 70% as a cathode of Li-S batteries exhibits the initial discharge capacity of 1354 mAh g-1 at 0.1 C, excellent rate capacity of 478 mAh g-1 at 3 C, admirable long-term cycling stability with a high reversible capacity of 414 mAh g-1 after 1000 cycles and low capacity decay rate of 0.035% per cycle. The designed three-dimensional network structure could lead to a quick diffusion of Li+/e- and a good impeding effect for polysulfides dissolution, which is beneficial for developing the advanced energy storage device of Li-S batteries.