| Kesterite Cu2ZnSnSe4?CZTSe?is considered as a promising absorber for solar cells owing to its large absorption coefficient(>104 cm-1),suitable band gap?Eg?1.0 eV?,low toxicity and abundance of constitute elements.In this paper,CZTSe thin films were fabricated by RF-magnetron sputtering a single quarteranry CZTSe target.The effects of sputtering parameters and annealing processes on the CZTSe properties have been studied systematically.Based on the optimization of the CZTSe deposition and annealing parameters,we fabricated the CZTSe thin film solar cell and memristor devices,and analyzed their performances in detail.The main achievements are shown as follows:?1?We systematically studied the effects of substrate temperature,sputtering power and sputtering pressure on the properties of deposited CZTSe thin films through a single target RF-magnetron sputtering process.We got the following results:?a?Substrate temperature affects the crystal quality of the deposited CZTSe films significantly,the optimized substrate temperature is 380?.The deposited CZTSe thin film exhibits excellent resistance uniformity.?b?Sputtering powder can adjust the composition of the CZTSe effectively;the sputtering powder density and the deposition rate exhibits almost linear relationship.?c?The film deposition rate increass first and then decreases as increasing the sputtering pressure,and the maximal deposition rate was obtain under 1.0 Pa.?2?The effects of annealing process on a single target RF-magnetron sputtered CZTSe thin films have been studied systematically,the results are as follow:?a?The crystal quality of the precursors impacts the crystal quality and surface morphology of the annealed CZTSe films significantly,the precursors with poor crystal quality were easy to decompose.?b?Compared to the films annealed in Se,precursors annealed in SnSe2 can improve the quality of the annealed CZTSe thin films more effectively,restraining film decomposition and enhancing the photoconductive performance.?c?The optimized annealing temperature is 480?when using SnSe2 as selenium source,the annealed films exhibit smooth and compact surface morphology with crystal size of approximately 1?m,and change of photoconductivity change as large as 28.1%,the carrier concentration of 8.20×1014 cm-3,and the mobility of 26.4 cm2·v-1·s-1.?3?CZTSe thin film solar cell and memristor devices have been fabricated based on the optimized CZTSe fabrication process,the results are as follow:?a?Device structure of ITO/i-ZnO/CdS/CZTSe/Mo was used to fabricate CZTSe thin film solar cells,the efficiency reaches 0.34%and the open voltage of 350 mV.?b?The solar cell possesses small density of shunt current(ISC=2.26 mA/cm2),this might attribute to the large series resistance of the device.The CZTSe absorber showed Zn poor and Sn rich composition,which would facilitate the formation of[2CuZn+SnZn]defects and aggravate the recombination of photo-generated carriers.?c?The memristor device with the structure of Metal/Cu2ZnSnSe4/Mo has been fabricated.The device exhibited long retention time of 104 s and HRS/LRS ratio of 215,indicating excellent resistive switching?RS?performance.At the same time,the negative differential resistance?NDR?behavior was also found at room temperature.?d?The combined action model of conductive filament and Schottky barrier reinstallment has been demonstrated to explain the NDR and RS coexistence phenomenon. |
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