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Polymer–polymer blends have been reported to exhibit exceptional thermal and ambient stability. However, power conversion efficiencies (PCEs) from devices using polymeric acceptors have been recorded to be significantly lower than those based on conjugated molecular acceptors. Herein, two organic nonfullerene bulk heterojunction (BHJ) blends ITIC:PBDB-T and N2200:PBDB-T, together with their fullerene counterpart, PCBM:PBDB-T, are adopted to understand the effect of electron acceptors on device performance. Free charge carrier properties using time-resolved microwave conductivity (TRMC) measurements are comprehensively investigated. The nonfullerene devices show an improved PCE of 10.06% and 6.65% in the ITIC- and N2200-based cells, respectively. In comparison, the PCBM:PBDB-T-based devices yield a PCE of 5.88%. The optimal N2200:PBDB-T produced the highest TRMC mobility, longest lifetime, and greatest free-carrier diffusion length. It is found that such phenomena can be associated with the unfavorable morphology of the all-polymer BHJ microstructure. In contrast, the solar cells using either the PCBM or ITIC acceptors display a more balanced donor and acceptor phase separation, leading to more efficient free-carrier separation and transport in the operating device. By sacrificing efficiency for superior stability, it is shown that the improved structure in all-polymer blend can deliver a more stable morphology under thermal stress.

This study explores the unsteady hybrid nanofluid (NF) flow consisting of cobalt ferrite (CoFe2O4) and copper (Cu) nano particulates with natural convection flow due to an expanding surface implanted in a porous medium. The Cu and CoFe2O4 nanoparticles (NPs) are added to the base fluid water to synthesize the hybrid NF. The effects of second-order velocity slip condition, chemical reaction, heat absorption/generation, temperature-dependent viscosity, and Darcy Forchheimer are also assessed in the present analysis. An ordinary differential equation system is substituted for the modeled equations of the problem. Further computational processing of the differential equations is performed using the parametric continuation method. A validation and accuracy comparison are performed with the Matlab package BVP4C. Physical constraints are used for presenting and reviewing the outcomes. With the increase in second-order velocity slip condition and unsteady viscosity, the rates of heat and mass transition increase significantly with the variation in Cu and Fe2O4 NPs. The findings suggest that the uses of Cu and Fe2O4 in ordinary fluids might be useful in the aerodynamic extrusion of plastic sheets and extrusion of a polymer sheet from a dye.

Posttreatment of titanium oxide (TiO2) using lithium (Li) and cobalt (Co) precursors is widely adopted to modify the charge quenching property in perovskite solar cells (PSCs); however, the fundamental understanding of the effect of the modification layer on the material itself and, consequently, the photovoltaic performance stability is not complete. In this work, in situ X‐ray diffraction measurements show that the Li and Co ions can diffuse into TiO2 and consequently accelerate the rutile phase transformation. X‐ray photoelectron spectroscopy results reveal the appearance of a Ti3+ feature in both the Li‐ and Co‐treated samples, suggesting that the treatment ions are partially located at the subsurface/surface of the spin‐cast TiO2 layer. The Li‐treated TiO2 exhibits greatly upshifted conduction band edges, which benefits charge extraction properties and improves the average device parameters in a complete PSC. To complement the experiments, density functional theory calculations are performed. While Li treatment initially results in enhanced electronic properties, Li‐treated TiO2 tends to have more surface vacancies over time and is more susceptible to adsorption and accumulation of iodide ions compared to the Co‐treated sample, which is experimentally supported by surface photovoltage spectroscopy and time‐resolved photoluminescence results. [ABSTRACT FROM AUTHOR]

Laser texturing process is a promising method to alter the wettability of metal surface on which micro/nano rough structures are created for changing the contact angle between the textured surface and liquid droplet. This paper aims at fabricating a superhydrophobic surface on AISI316L stainless steel, and a nanosecond pulse laser was employed for texturing line and point patterns on the metal surface. The influences of texturing patterns, laser power, scan speed, irradiation duration, and aging hours on the water contact angle and morphology of workpiece surface were investigated. According to the results, the hydrophilic surface was obtained right after the texturing process, and the surface turned to be hydrophobic after being left in ambient air for 15 days. The aging of laser-textured surface was also performed to induce the chemisorption of hydrocarbons toward the surface. This post process was able to shorten the hydrophilic-to-hydrophobic transition from days to a few hours. The aging duration of 2 and 0.5 h was respectively recommended for yielding and stabilizing the superhydrophobicity on line- and point-patterned surfaces. The maximum contact angle of 159.61° was achievable when the point pattern was textured on the stainless steel surface by using the laser power of 10 W and irradiation duration of 0.18 ms. [ABSTRACT FROM AUTHOR]

A simple deposition process for preparing crystalline semiconductors with low degrees of disorder is of paramount interest for both device applications and research investigations. This study centers on the ultrasonically sprayedaerosol based approach for preparing crystals of methylammonium lead trihalide perovskite (CH3NH3PbI3). The surface photovoltage (SPV) spectra are found to depend strongly on the preparation conditions, with the SPV signals (below the material's band gap) providing information on the defect states. The measured values of tail states near the band gap (Et) are found to be about 21 and 52 meV for the CH3NH3PbI3 crystals prepared by the ultrasonically sprayed-on and spun casting approaches, respectively. [ABSTRACT FROM AUTHOR]