A two-photon-activatable photoacid generator, based on a bis[(diarylamino) styryl]benzene core with covalently attached sulfonium moieties, has been synthesized. The photoacid generator has both a large two-photon absorption cross section (delta = 690 x 10(-50) centimeter(4) second per photon) and a high quantum yield for the photochemical generation of acid (phiH+ = 0.5). Under near-infrared laser irradiation, the molecule produces acid after two-photon excitation and initiates the polymerization of epoxides at an incident intensity that is one to two orders of magnitude lower than that needed for conventional ultraviolet-sensitive initiators. This photoacid generator was used in conjunction with a positive-tone chemically amplified resist for the fabrication of a three-dimensional (3D) microchannel structure.
In this article, pure phase metastable wurtzite Cu 2 ZnSnS 4 (CZTS) nanocrystals (NCs) were synthesized by a facile one-pot method. When pure 1dodecanethiol (DDT) was used as the solvent, two coexisting CZTS phases (wurtzite and kesterite) were found. When an increased amount of oleylamine (OAm) was added to DDT, kesterite CZTS disappeared gradually, and the asobtained CZTS NCs became smaller and more uniform. When 0.5 mL of OAm was added, rice-like pure phase metastable wurtzite CZTS NCs were obtained. The factors, including amount of OAm, reaction temperature, reaction time, and concentration of precursors, which influence the morphology, size, and monodispersity of CZTS NCs, were studied in detail. The results showed OAm played an important role in the formation of the final pure phase metastable wurtzite NCs. Time-dependent experiments were performed to observe the growth of CZTS NCs. The final CZTS NCs evolved from spherical-like Cu 2 S NCs through rhombuslike intermediate shaped NCs to rice-like pure wurtzite CZTS NCs. On the basis of the detailed time-dependent shape and elemental composition evolutions, a possible asynchronous doping growth and formation mechanism was proposed. The optical and electrical properties of the pure wurtzite CZTS NCs were also investigated. The band gap of the rice-like CZTS is about 1.49 eV, which approaches the optimum value for solar photoelectric conversion. Meanwhile, the current−voltage characteristics and Hall effect measurement of the wurtzite CZTS NCs films indicated that rice-like CZTS NCs favored the electronic transmission and thus may induce the generation of photocurrent. Thus, the obtained wurtzite CZTS NCs are more suitable for using as absorber layer in low cost solar cells.
The partial substitution of Cu with Ag into the host lattice of CuZnSn(S,Se) thin films can reduce the open-circuit voltage deficit (V) of CuZnSn(S,Se) (CZTSSe) solar cells. In this paper, elemental Cu, Ag, Zn, Sn, S, and Se powders were dissolved in solvent mixture of 1,2-ethanedithiol (edtH) and 1,2-ethylenediamine (en) and used for the formation of (CuAg)ZnSn(S,Se) (CAZTSSe) thin films with different Ag/(Ag + Cu) ratios. The key feature of this approach is that the impurity atoms can be absolutely excluded. Further results indicate that the variations of grain size, band gap, and depletion width of the CAZTSSe layer are generally determined by Ag substitution content. Benefiting from the V enhancement (∼50 mV), the power conversion efficiency is successfully increased from 7.39% (x = 0) to 10.36% (x = 3%), which is the highest efficiency of Ag substituted devices so far.
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