•Solar cell performance enhanced by adding dichloromethane to 1,2 o-dichlorobenzene.•The crystallization of P3HT increased in competing solvent evaporation process.•The film surface composition was tuned from P3HT-rich to more favored PCBM-rich.•The charge transfer at the active layer-cathode interface was optimized.In this work, the effects of mixed solvents on donor–acceptor vertical phase separation and light absorption was investigated. By using mixed orthogonal solutions of 1,2 o-dichlorobenzene (o-DCB) and dichloromethane (DCM), a PCBM([6,6]-phenyl-C61-butyric acid methyl ester)-rich top layer was induced in typical poly(3-hexylthiophene-2,5-diyl)(P3HT):PCBM bulk heterojunction structure. By carefully adjusting the o-DCB:DCM volume ratio, the contact between active layer and the Al cathode was significantly improved due to the precipitation of PCBM on the top surface, which resulting in an electron transport preferable interface between the active layer and cathode. Meanwhile, light absorption was also effectively improved due to the increased crystallinity of polymers under mixed solvents. Overall, the short circuit current was greatly increased, and the efficiency was improved from 3.07% in the control sample to 3.97% by adding 30% DCM. The detailed mechanism of the formation of PCBM-rich layer and enhanced light absorption with o-DCB:DCM solution was expatiated. Our findings suggest a facile spin coating method to fabricate efficient BHJ solar cells, which can pave the way for the large scale application of organic photovoltaic devices (OPVs) in the future.Graphical abstract

The composition and annealing temperature dependence of magnetic domain structures in sputtered magnetoresistance (Ni74Fe16Co10)xAg1−x (x=9–41 at.%) granular films were studied by magnetic force microscopy. X-ray diffraction results showed that the annealed (Ni74Fe16Co10)xAg1−x films consisted of body-centered cubic NiFeCo alloy nanocrystals embedded in the face-centered cubic Ag matrix. Both short-range and long-range magnetic structures were observed in these films. It was found that the short-range magnetic structures with single domains corresponded to the highest giant magnetoresistance values, while the long-range magnetic structures with larger domain dimensions corresponded to the lower values.

CoxC1−x (x=0.18, 0.25, 0.39) nanogranular films were prepared by pulsed filtered vacuum arc deposition. Subsequent thermal annealing was performed in a vacuum furnace (∼8×10−4 Pa) at various temperatures. The microstructural evolution of the films was characterized by non-Rutherford backscattering spectrometry, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that the as-deposited films with various Co concentrations are amorphous. Upon annealing, nanocrystalline Co grains were formed, while the carbon content remained amorphous. The electrical resistance of the films was measured as a function of temperature between 20 and 300 K, using a conventional four-point probe DC technique. While the as-deposited films were metallic in the measured temperature range, annealed films showed complicated transport properties, depending on both the Co concentration and the annealing temperature. Experimental results are compared to the general predictions of theories of weak localization and/or electron–electron interaction on the metallic side of the metal-insulator transition, and thermally assisted hopping or tunneling on the insulating side of the transition.