Pinjiang Li

Dual Influence of Reduction Annealing on Diffused Hematite/FTO Junction for Enhanced Photoelectrochemical Water Oxidation

Band structure engineering of the interface between the semiconductor and the conductive substrate may profoundly influence charge separation and transport for photovoltaic and photoelectrochemical devices. In this work, we found that a reduction-annealing treatment resulted in a diffused junction through enhanced interdiffusion of hematite/FTO at the interface. The activated hematite exhibited higher nanoelectric conductivity that was probed by a PeakForce TUNA AFM method. Furthermore, charge accumulation and recombination via surface states at the interface were dramatically reduced after the reduction-annealing activation, which was confirmed by transient surface photovoltage measurements. The diffused hematite junction promises improved photoelectrochemical performance without the need for a buffer layer.

Design and synthesis of ternary semiconductor Cu7.2(SexS1−x)4 nanocrystallites for efficient visible light photocatalysis

A new series of ternary semiconductor compounds, Cu7.2(SexS1−x)4 (0.2 ≤ x ≤ 0.8) nanocrystallites, that exhibited good photocatalytic activity under visible-light irradiation, were facilely synthesized under mild conditions. The Cu7.2(SexS1−x)4 nanocrystallites were characterized by powder X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and UV-Vis absorption spectra. From X-ray data it is found that the cell constant a of different samples varies linearly with the composition x as: a (A) = 5.5959 + 0.1586x. UV-Vis absorption spectra indicate that the apparent band gap energies can be tuned by adjusting the composition x so as to better match to the whole solar spectrum. Unlike the most studied TiO2 that only responds to the UV-light irradiation, the present Cu7.2(SexS1−x)4 nanocrystallites exhibited much better photocatalytic activity under visible light on degradation of RhB. It is believed that the photocatalytic superiority of the Cu7.2(SexS1−x)4 nanocrystallites is mainly due to the compositional gradient arisen from uneven distribution of Se/S compositions in the compounds, which may induce a more efficient charge separation/transport in the Cu7.2(SexS1−x)4 photocatalysts.

Heavy doping of S2 in Cu7.2S4 lattice into chemically homogeneous superlattice Cu7.2Sx nanowires: strong photoelectric response

This is the first time a series of chemically homogeneous superlattice Cu7.2Sx (x = 4.07, 4.52, 6.01, 6.20, 6.45) nanowires have been successfully synthesized by heavy doping of S2 species in Cu7.2S4 lattice through a simple wet-chemical route. This superlattice structure is a polytypoid structure tuned by adjusting the atom ratio of S2 to S in lattice configuration. The perfect superlattice Cu7.2S6.20 structure interestingly consists of two alternating lattice fringes corresponding to the atom layers of Cu–S and Cu–S2 in an even spacing of 5.70 A. The article describes the formation, morphology, composition and structure of the Cu7.2Sx superlattice nanowires. Photoluminescence (PL) spectra and transient photovoltage (TPV) measurements reveal that the generation and separation efficiency of the photogenerated charges of Cu7.2Sx nanowires could be greatly improved by adjusting the S2/S ratio in the lattice configuration, and thus enhance the luminescence quantum efficiency. This study reveals that the S2 species in Cu7.2Sx nanowires play a very important role in determining the dynamic properties of photogenerated charge carriers.

Doping Zn2+ in CuS Nanoflowers into Chemically Homogeneous Zn0.49Cu0.50S1.01 Superlattice Crystal Structure as High-Efficiency n-Type Photoelectric Semiconductors

Doping Zn(2+) in CuS nanoflower into chemically homogeneous superlattice crystal structure is proposed to convert p-type CuS semiconductor to an n-type CuS semiconductor for significantly enhanced photoelectric response performance. In this study, the chemically homogeneous Zn-doped CuS nanoflowers (Zn0.06Cu0.94S, Zn0.26Cu0.73S1.01, Zn0.36Cu0.62S1.02, Zn0.49Cu0.50S1.01, Zn0.58Cu0.40S1.02) are synthesized by reacting appropriate amounts of CuCl and Zn(Ac)2·2H2O with sulfur powders in ethanol solvothermal process. By tuning the Zn/Cu atomic ratios to ∼1:1, the chemically homogeneous Zn-doped CuS nanoflowers could be converted to the perfect Zn0.49Cu0.50S1.01 superlattice structure, corresponding to the periodic Cu-S-Zn atom arrangements in the entire crystal lattice, which can induce an effective built-in electric field with n-type semiconductor characteristics to significantly improve the photoelectric response performance, such as the lifetime of photogenerated charge carriers up to 6 × 10(-8)-6 × 10(-4) s with the transient photovoltage (TPV) response intensity to ∼44 mV. This study reveals that the Zn(2+) doping in CuS nanoflowers is a key factor in determining the superlattice structure, semiconductor type, and the dynamic behaviors of charge carriers.

Synthesis of Sb2S3 films on conducting substrate and its application in hybrid solar cell devices

Antimony sulfide (Sb2S3) films on indium-doped tin oxide (ITO) glass substrates are easily synthesized by a solvothermal method from Sb ultrathin films and S powder as antimony and sulfur source, respectively. The crystalline Sb2S3 films were characterized using X-ray powder diffraction (XRD) and Raman spectroscopy. The Sb2S3 films are composed of micro-flakes of Sb2S3. The composite of Sb2S3 film and ITO substrate were used to fabricate the solar cell device (ITO/Sb2S3:P3HT/Au), and I–V measurement of the device was performed. Under the optimized condition, the solar conversion efficiency is 0.0026% at 1 sun illumination.