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Cu2ZnSnS4 (CZTS) films with high-quality are necessary to the high-performance CZTS solar cells. The influence of different temperature-time profiles during sulfurization on CZTS films were investigated by characterizing the compactness, roughness and grain size of CZTS films. With slowing the heating-rate during sulfurization process, the grain size of the film is becoming larger and larger, but the large grain size degrades the flatness of the CZTS films at the same time. The formation of films having the target composition (EDX) and phase purity (Raman) was attributed to the optimum choice of composition ration of the precursor and the thermal profile during sulfurization. The optical and electrical properties of corresponding CZTS films were detected by using UV–vis–INR Spectrophotometer and Hall measurement, respectively. Finally, the CZTS film solar cells were fabricated and the best cell demonstrated 3.91% efficiency. A high Rs is the main reason to inhibit the performance of the cells.

The kesterite compound Cu2ZnSnS4(CZTS) is one of the most interesting materials for absorber layers of thin-film solar cells,not only because it is composed of earth abundant and non-toxic elements,but also owing to the fact that its absorption coefficient is high (on the order of 104 cm-1) and its optimal band gap is 1.5 eV for single-junction solar cells. Plenty of methods are used to deposit the CZTS layer,such as evaporation,sputtering,spray-pyrolysis,sol-gel, pulsed laser deposition and electro-chemical deposition.Among these methods,sputtering is considered as one of the most viable deposition techniques for producing a large-scale panel of thin film solar cells with demonstrable productivity and easy adjustment.In this paper,Cu2ZnSnS4 thin films are prepared by in-situ annealing after being sputtered with a quaternary compound target.This technology can reduce the extrinsic defects in the thin film.It is desirable to control the growth of grain boundary,increase grain size and make the thin film more compact and smooth. The in-situ annealing is a method which can heat a work piece fast to a certain temperature and maintain the temperature for some time after sputtering.As is well known,one of the major reasons for affecting CZTS device performance is the low open circuit voltage (Voc),and it is also a challenge to obtain a high value because there are a lot of defect states at the grain boundaries.The experiment shows that using the method of in-situ annealing after sputtering can obtain large size grains and smooth and compact surface.The obtained thin films are Cu-poor,Zn-rich and Sn-poor,which can restrain the Cu vacancies (VCu) and anti-site defects (CuZn,SnZn,and SnCu).The free carrier concentration (NA) increases with the increase of Zn content,while the open circuit voltage of CZTS solar cells increases with the increase of NA. In order to develop CZTS solar cells based on the thin films,the n-type CdS buffer layer (70 nm) is grown using chemical bath deposition,and intrinsic ZnO (70 nm) and ZnO:Al (250 nm) films are deposited by RF-magnetron sputtering.In the end,Ni-Al metal grids as the top electrode are prepared by thermal evaporation.The final solar cells with an active area of 0.25 cm2 are determined by mechanical scribing.The solar cell based the CZTS film with in-situ annealing has better-performance parameters,its open circuit voltage and short-circuit current density are 575 mV and 8.32 mA/cm2,respectively.The photoelectric conversion efficiency of 1.82% is achieved.In order to enhance the efficiency of device,it is important to minimize Cu/Zn disorder in CZTS film and control the element composition by optimizing high-temperature crystallization process.The relevant research work on reducing defects in the films,increasing the carrier collection and enhancing the Jsc is under way. This method not only avoids the contamination caused by the external annealing but also simplifies the preparation process of the thin film,which greatly saves the preparation time of the solar cell and is beneficial to industrial production.annealing is a method which can heat a work piece fast to a certain temperature and maintain the temperature for some time after sputtering.As is well known,one of the major reasons for affecting CZTS device performance is the low open circuit voltage (Voc),and it is also a challenge to obtain a high value because there are a lot of defect states at the grain boundaries.The experiment shows that using the method of in-situ annealing after sputtering can obtain large size grains and smooth and compact surface.The obtained thin films are Cu-poor,Zn-rich and Sn-poor,which can restrain the Cu vacancies (VCu) and anti-site defects (CuZn,SnZn,and SnCu).The free carrier concentration (NA) increases with the increase of Zn content,while the open circuit voltage of CZTS solar cells increases with the increase of NA. In order to develop CZTS solar cells based on the thin films,the n-type CdS buffer layer (70 nm) is grown using chemical bath deposition,and intrinsic ZnO (70 nm) and ZnO:Al (250 nm) films are deposited by RF-magnetron sputtering.In the end,Ni-Al metal grids as the top electrode are prepared by thermal evaporation.The final solar cells with an active area of 0.25 cm2 are determined by mechanical scribing.The solar cell based the CZTS film with in-situ annealing has better-performance parameters,its open circuit voltage and short-circuit current density are 575 mV and 8.32 mA/cm2,respectively.The photoelectric conversion efficiency of 1.82% is achieved.In order to enhance the efficiency of device,it is important to minimize Cu/Zn disorder in CZTS film and control the element composition by optimizing high-temperature crystallization process.The relevant research work on reducing defects in the films,increasing the carrier collection and enhancing the Jsc is under way. This method not only avoids the contamination caused by the external annealing but also simplifies the preparation process of the thin film,which greatly saves the preparation time of the solar cell and is beneficial to industrial production.