Understanding the modulation effect and surface chemistry in a heteroatom incorporated graphene-like matrix toward high-rate lithium-sulfur batteries.

The underlying interface effects of sulfur hosts/polysulfides at the molecular level are of great significance to achieve advanced lithium-sulfur batteries. Herein, we systematically study the polysulfide-binding ability and the decomposition energy barrier of LiS enabled by different kinds of nitrogen (pyridinic N, pyrrolic N and graphitic N) and phosphorus (P-O, PO and graphitic P) doping and decipher their inherent modulation effect. The doping process helps in forming a graphene-like structure and increases the micropores/mesopores, which can expose more active sites to come into contact with polysulfides.

Gamma-radiated biochar carbon for improved supercapacitor performance.

Biochar carbon YP-50 exposed to gamma radiation at 50 kGy, 100 kGy, and 150 kGy was used as an electrode for an electric double-layer capacitor. The gamma radiation affected the pore structure and pore volume of the biochar electrodes. The optimized surface morphology, pore structure, and pore volume of the biochar with an irradiation dose of 100 kGy showed outstanding specific capacitance of 246.

Transparent MoS/PEDOT Composite Counter Electrodes for Bifacial Dye-Sensitized Solar Cells.

Dye-sensitized solar cells (DSSCs) are solar energy conversion devices with high efficiency and simple fabrication procedures. Developing transparent counter electrode (CE) materials for bifacial DSSCs can address the needs of window-type building-integrated photovoltaics (BIPVs). Herein, transparent organic-inorganic hybrid composite films of molybdenum disulfide and poly(3,4-ethylenedioxythiophene) (MoS/PEDOT) are prepared to take full advantage of the conductivity and electrocatalytic ability of the two components.

Efficient tandem solar cells with solution-processed perovskite on textured crystalline silicon.

Stacking solar cells with decreasing band gaps to form tandems presents the possibility of overcoming the single-junction Shockley-Queisser limit in photovoltaics. The rapid development of solution-processed perovskites has brought perovskite single-junction efficiencies >20%. However, this process has yet to enable monolithic integration with industry-relevant textured crystalline silicon solar cells.

Modifying Mesoporous TiO by Ammonium Sulfonate Boosts Performance of Perovskite Solar Cells.

Mesoporous-structure perovskite solar cells (meso-PVKSCs) have been widely utilized due to the achieved high efficiency for which the TiO layer usually suffers from sufficient electron trap states, low electron mobility, and inavoidable catalytic activity. Herein, a mesoporous TiO (m-TiO) layer is modified by tetraethylammonium -toluenesulfonate (abbreviated as TEATS) for the first time, leading to a significant photoelectric conversion efficiency enhancement from 19.14 to 20.

Photovoltaic Counter Electrodes: An Alternative Approach to Extend Light Absorption Spectra and Enhance Performance of Dye-Sensitized Solar Cells.

If counter electrodes (CEs) could also contribute to light harvesting in dye-sensitized solar cells (DSSCs), then the power conversion efficiency (PCE) of DSSCs would be further boosted without changing the device structure. Nearly monodispersed Ag Se nanocrystals with a bandgap of 1.62 eV (∼765 nm) were synthesized via a one-pot process, and Ag Se CEs were fabricated by using a spin-coating and annealing process.

Fluorinated hybrid solid-electrolyte-interphase for dendrite-free lithium deposition.

Lithium metal anodes have attracted extensive attention owing to their high theoretical specific capacity. However, the notorious reactivity of lithium prevents their practical applications, as evidenced by the undesired lithium dendrite growth and unstable solid electrolyte interphase formation. Here, we develop a facile, cost-effective and one-step approach to create an artificial lithium metal/electrolyte interphase by treating the lithium anode with a tin-containing electrolyte.

Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells.

Polymer aggregation and crystallization behavior play a crucial role in the performance of all-polymer solar cells (all-PSCs). Gaining control over polymer self-assembly via molecular design to influence bulk-heterojunction active-layer morphology, however, remains challenging. Herein, we show a simple yet effective way to modulate the self-aggregation of the commonly used naphthalene diimide (NDI)-based acceptor polymer (N2200), by systematically replacing a certain amount of alkyl side-chains with compact bulky side-chains (CBS).

Improving Performance of Nonfullerene Organic Solar Cells over 13% by Employing Silver Nanowires-Doped PEDOT:PSS Composite Interface.

Ag nanowires (NWs)/PEDOT:PSS composite was prepared by a facile solution-processing method and employed as anode interface in nonfullerene organic solar cells (OSCs). In the presence of a Ag NWs (5%, v/v%)/PEDOT:PSS interfacial layer, a high-power conversion efficiency up to 13.53% was achieved based on a PBDB-T-2Cl:IT-4F photoactive layer system, much higher than the efficiency of the controlled counterpart device with pristine PEDOT:PSS as anode modifier.

SbS Thickness-Related Photocurrent and Optoelectronic Processes in TiO/SbS/P3HT Planar Hybrid Solar Cells.

In this work, a comprehensive understanding of the relationship of photon absorption, internal electrical field, transport path, and relative kinetics on SbS photovoltaic performance has been investigated. The n-i-p planar structure for TiO/SbS/P3HT heterojunction hybrid solar cells was conducted, and the photon-to-electron processes including illumination depth, internal electric field, drift velocity and kinetic energy of charges, photo-generated electrons and hole concentration-related surface potential in SbS, charge transport time, and interfacial charge recombination lifetime were studied to reveal the key factors that governed the device photocurrent. Dark J-V curves, Kelvin probe force microscope, and intensity-modulated photocurrent/photovoltage dynamics indicate that internal electric field is the main factors that affect the photocurrent when the SbS thickness is less than the hole diffusion length.

Employing PCBTDPP as an Efficient Donor Polymer for High Performance Ternary Polymer Solar Cells.

A compatible low-bandgap donor polymer (poly[N-90-heptadecanyl-2,7carbazole-alt-3,6-bis(thiophen-5-yl)-2,5-dioctyl-2,5-dihydropyrrolo [3,4] pyrrole-1,4-dione], PCBTDPP) was judicially introduced into the archetypal poly(3-hexylthiophene):[6,6]-phenyl-C-butyric acid methyl ester (P3HT:PCBM) photoactive system to fabricate highly efficient ternary based bulk heterojunction polymer solar cells (PSCs). The PCBTDPP ternary-based PSC with optimal loading (0.2 wt.

High-performance carbon electrode-based CsPbIBr inorganic perovskite solar cell based on poly(3-hexylthiophene)-carbon nanotubes composite hole-transporting layer.

CsPbIBr inorganic perovskite has been considered as a promising candidate for application in photovoltaic devices due to its high thermal stability and reasonable bandgap of 1.92 eV. However, CsPbIBr perovskite is sensitive to moisture, which remarkably deteriorates the stability of CsPbIBr perovskite solar cells under the ambient conditions.

Nanoscale charge transport and local surface potential distribution to probe defect passivation in Ag doped CuZnSnS absorbing layer.

The performance of earth abundant CuZnSnS (CZTS) material is limited by high deficit of open circuit voltage (V) which is mainly due to the easy formation of Cu antisite defects. Suppression of Cu defects is thus inevitably required for further developments in CZTS based solar cells. We studied systematic increase of Ag doping in CZTS thin film and investigated the nanoscale electrical properties using Kelvin probe force microscopy and current sensing atomic force microscopy (CAFM) to probe Cu defects.

Hierarchical Nanosheet-Based MS (M = Re, Mo, W) Nanotubes Prepared by Templating Sacrificial Te Nanowires with Superior Lithium and Sodium Storage Capacity.

Hierarchical nanosheet-based nanotubes are very attractive because their unique structure endows them with large surface areas and exposes massive active sites for functional applications. We herein demonstrate a facile one-pot hydrothermal approach to fabricate the hierarchical nanosheet-based MS (M = Re, Mo, W) nanotubes by using Te nanowires as sacrificial templates. The hierarchical nanotubes show tube channels of ∼30 nm and hierarchical channel walls with a tunable thickness of up to ∼50 nm.

Functionalized carboxylate deposition of triphenylamine-based organic dyes for efficient dye-sensitized solar cells.

The standard dip-coating dye-loading technique for dye-sensitized solar cells (DSSCs) remains essentially unchanged since modern DSSCs were introduced in 1991. This technique constitutes up to 80% of the DSSC fabrication time. Dip-coating of DSSC dyes not only costs time, but also generates a large amount of dye waste, necessitates use of organic solvents, requires sensitization under dark conditions, and often results in inefficient sensitization.

Self-recovery in Li-metal hybrid lithium-ion batteries via WO reduction.

It has been a challenge to use transition metal oxides as anode materials in Li-ion batteries due to their low electronic conductivity, poor rate capability and large volume change during charge/discharge processes. Here, we present the first demonstration of a unique self-recovery of capacity in transition metal oxide anodes. This was achieved by reducing tungsten trioxide (WO3) via the incorporation of urea, followed by annealing in a nitrogen environment.

Noncovalent phosphorylation of graphene oxide with improved hole transport in high-efficiency polymer solar cells.

Graphene oxide (GO) has been extensively applied as an alternative hole transport layer (HTL) of bulk heterojunction polymer solar cells (BHJ-PSCs) with the function of selectively transporting holes and blocking electrons, but suffers from low electrical conductivity. Herein, using phosphorus pentoxide (P2O5) dissolved in methanol as a precursor, we successfully modified GO via noncovalent phosphorylation for the first time, which showed improved hole transport in BHJ-PSCs compared to the pristine GO. As a result, BHJ-PSC devices based on noncovalently phosphorylated GO (P-GO) HTL show dramatically higher power conversion efficiencies (7.

Bias-Dependent Normal and Inverted J- V Hysteresis in Perovskite Solar Cells.

Perovskite solar cells (PSCs) typically exhibit hysteresis in current density-voltage ( J- V) measurements. The most common type of J- V hysteresis in PSCs is normal hysteresis, in which the performance in the reverse scan is better than that in the forward scan. However, inverted hysteresis also exists, in which the reverse scan performance is worse than in the forward scan; this hysteresis, however, is significantly less well studied.

Influence of Nonfused Cores on the Photovoltaic Performance of Linear Triphenylamine-Based Hole-Transporting Materials for Perovskite Solar Cells.

The core plays a crucial role in achieving high performance of linear hole transport materials (HTMs) toward the perovskite solar cells (PSCs). Most studies focused on the development of fused heterocycles as cores for HTMs. Nevertheless, nonfused heterocycles deserve to be studied since they can be easily synthesized.

Solution-processed all-oxide bulk heterojunction solar cells based on CuO nanaorod array and TiO nanocrystals.

We present a method to synthesize CuO nanorod array/TiO nanocrystals bulk heterojunction (BHJ) on fluorine-tin-oxide (FTO) glass, in which single-crystalline p-type semiconductor of the CuO nanorod array is grown on the FTO glass by hydrothermal reaction and the n-type semiconductor of the TiO precursor is filled into the CuO nanorods to form well-organized nano-interpenetrating BHJ after air annealing. The interface charge transfer in CuO nanorod array/TiO heterojunction is studied by Kelvin probe force microscopy (KPFM). KPFM results demonstrate that the CuO nanorod array/TiO heterojunction can realize the transfer of photo-generated electrons from the CuO nanorod array to TiO.

Improving Photovoltaic Properties of P3HT:ICBA through the Incorporation of Small Molecules.

We investigated the role of a functional solid additive, 2,3-dihydroxypyridine (DHP), in influencing the optoelectronic, morphological, structural and photovoltaic properties of bulk-heterojunction-based polymer solar cells (BHJ PSCs) fabricated using poly(3-hexylthiophene): indene-C bisadduct (P3HT:ICBA) photoactive medium. A dramatic increase in the power conversion efficiency (~20%) was witnessed for the BHJ PSCs treated with DHP compared to the pristine devices. A plausible explanation describing the alignment of pyridine moieties of DHP with the indene side groups of ICBA is presented with a view to improving the performance of the BHJ PSCs via improved crystalline order and hydrophobicity changes.

Synthesis, Photophysical and Computational Study of Novel Coumarin-based Organic Dyes.

A series of novel coumarin pyrazoline moieties combined with tetrazoles, 3-(1-phenyl-4-(1H-tetrazol-5-yl)-1H-pyrazol-3-yl)-2H-chromen-2-one, 6-chloro-3-(1-phenyl-4-(1H-tetrazol-5-yl)-1H-pyrazol-3-yl)-2H-chromen-2-one, 6-bromo-3-(1-phenyl-4-(1H-tetrazol-5-yl)-1H-pyrazol-3-yl)-2H-chromen-2-one and 6-bromo-3-(1-(4-bromophenyl)-4-(1H-tetrazol-5-yl)-1H pyrazol-3-yl)-2H-chromen-2-one7(a-d), were designed and synthesized. Single crystal X-ray diffraction and their interactions were studied by Hirshfeld surface analysis. Thermal stabilities and electrochemical properties of these compounds were examined from differential scanning calorimetry (DSC), thermogravimetric (TGA) and cyclic voltammetric (CV) studies.

Environmentally Friendly Plasma-Treated PEDOT:PSS as Electrodes for ITO-Free Perovskite Solar Cells.

Solution processed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) transparent electrodes (TEs) offer great potential as a low cost alternative to expensive indium tin oxide (ITO). However, strong acids are typically used for enhancing the conductivity of PEDOT:PSS TEs, which produce processing complexity and environmental issues. This work presents an environmentally friendly acid free approach to enhance the conductivity of PEDOT:PSS using a light oxygen plasma treatment, in addition to solvent blend additives and post treatments.

Nonconjugated Polymer Poly(vinylpyrrolidone) as an Efficient Interlayer Promoting Electron Transport for Perovskite Solar Cells.

The interfaces between perovskite layer and electrodes play a crucial role on efficient charge transport and extraction in perovskite solar cells (PSCs). Herein, for the first time we applied a low-cost nonconjugated polymer poly(vinylpyrrolidone) (PVP) as a new interlayer between PCBM electron transport layer (ETL) and Ag cathode for high-performance inverted planar heterojunction perovskite solar cells (iPSCs), leading to a dramatic efficiency enhancement. The CHNHPbICl-based iPSC device incorporating the PVP interlayer exhibited a power conversion efficiency (PCE) of 12.