Guilin Chen

The effects of SnS2 secondary phases on Cu2ZnSnS4 solar cells: a promising mechanical exfoliation method for its removal

The inhibition and removal of the SnS2 impurity phase in the kesterite Cu2ZnSnS4 (CZTS) layer is a major challenge for the improvement of CZTS solar cells; this impurity phase can critically damage device performance by forming a diode and a barrier for carrier collection. However, the formation and growth mechanism of SnS2 is incomplete and the common etching treatment with (NH4)2S is problematic because of its toxic characteristics. In this study, the formation and growth of large-size SnS2 sheets were observed to occur on the surface of the CZTS thin film via condensation during the cooling process. Sequently, a novel and benign peeling process was carried out using a sticky tape to effectively remove the SnS2 formed on the surface, resulting in a uniform CZTS thin film. A maximum efficiency of 4.3% of the oxides-derived CZTS device was obtained after this mechanical exfoliation, which is nearly eleven times that of the device without stripping. It was confirmed that this surface treatment is an effective and green way to remove the SnS2 impurity, which largely improved the performance of the CZTS device and may guide the preparation of pure phase CZTS thin films.

Engineering crystal orientation of p-Cu2O on heterojunction solar cells

ABSTRACT The Cu2O/AZO heterojunction solar cells were successfully constructed by synthesising p-Cu2O layer upon AZO using the electrochemical deposition method. The p-Cu2O nanostructures with different grain shape and preferred crystal orientation, including (100), (110) and (111) indicated by SEM and XRD, were obtained by controlling electrodeposition bath pH. The J–V characteristic shows that the performance of the Cu2O/AZO heterojunction solar cells is found to be dependent on the crystal orientation of p-Cu2O. Only the solar cell with Cu2O (111) exhibits well-defined rectifying behaviour and good photoelectric conversion efficiency, which may due to the optimised energy band structure of Cu2O (111)/AZO heterojunction solar cells . Furthermore, VOC and JSC were sharply increased by further optimising energy band structure through inserting the intrinsic ZnO layer between the Cu2O (111) and AZO. Therefore, the results illustrated above may offer a helpful guidance to design and construct the high performance solar cell.

Ultra-high sulfurization temperature drives the growth of oxide-derived Cu2ZnSnS4 thin film with very large grain

Small grain size is one of the main obstacles for preparing high efficiency Cu2ZnSnS4 (CZTS) photovoltaic devices. The high thermal energy (high annealing temperature) is used to facilitate the driving force of grain growth. In this paper, the CZTS thin films were synthesized by means of sulfurizing oxide-precursors at relatively high sulfurization temperatures (550–700 °C). The effect of sulfurization temperature on properties of CZTS thin films was investigated through XRD, Raman, SEM, and energy dispersive x-ray spectroscopy. Both the crystallinity of the CZTS films and the size of their grains were greatly enhanced, which is attributed to the acceleration of atomic inter-diffusion during the growing process of thin films under ultra-high temperature.

Synthesis and characterization of TiO2 photoanode treated by tetrabutyl titanate sol for DSSC application

As one typical example of third-generation thin-film solar cells, Dye-sensitized Solar Cell (DSSC) has become a research hot-spot because of its advantages. As a basic electron transport material, the modification of the nano-crystalline TiO2 would have remarkable influence on the cell. In this work, the scattering layer was firstly fabricated on the conductive glass substrate by sol–gel dip-coating method for the stable and high efficiency conventional DSSC. And the effect of the modification of the nanocrystalline TiO2 photoanode by the tetrabutyl titanate sol was investigated. Practically, the cell with photoanode modified by tetrabutyl titanate sol obviously presents higher light-electric conversion efficiency.

Preparation of Cu2ZnSnS/Se4 Thin Films from Oxide Precursors and its Prospect for Other Cu2MSnS4 Thin Films

In this chapter, the preparation of Cu2ZnSnSe4 (CZTSe) and Cu2ZnSnS4 (CZTS) thin films from oxide precursors was described. Such an oxides‐based route is a low cost, facile way for the kesteries thin films. The rationality of applying oxides method into CZTSe and CZTS thin films was also clarified, including the reactive thermodynamics and anneal‐ ing process. Finally, this oxide‐based approach is also expected for the preparation of the other Cu2MSnS4 (M= Co2+, Fe2+, Ni2+, Mn2+) thin films.

Synthesis and Characterization of Porous TiO2 Thin Film Loaded with Cu2ZnSnS4 Nanoparticles

As a promising absorber layer, semiconducting Cu2ZnSnS4 (CZTS) can be applied to replace the organic dye in dye-sensitized solar cell for photovoltaic application because of its good stability, suitable band gap energy (~1.5eV) and large absorption coefficient (~104 cm-1). In this paper, successive ionic layer adsorption and reaction (SILAR) method was utilized to deposit CZTS nanoparticles on mesoporous titanium dioxide (TiO2). This solar cell with carbon film coated FTO glass slide as the back electrode showed an open circuit voltage of 380 mV. Preliminary results obtained for solar cells fabricated with this material are promising.