退火温度对铜铟镓硒薄膜电学性能的影响

Influence of Annealing Temperature on Electric Properties of CuIn_(1-x)Ga_xSe_2 Thin Films

使用磁控溅射铜铟镓硒(CuIn1-xGaxSe2,CIGS)四元陶瓷靶材制备沉积态预制膜,在240-550℃对预制膜进行退火处理,着重研究了退火温度对薄膜电学性能(载流子浓度及迁移率)的影响。结果表明:退火温度低于270℃时薄膜中存在CuSe低电阻相,CIGS薄膜的载流子浓度在1017-1019cm-3,迁移率在0.1 cm2·V-1·s-1左右,不适于作为太阳电池的吸收层;当退火温度高于410℃时薄膜中不存在CuSe相,薄膜具有10 cm2·V-1·s-1左右的较高迁移率,载流子浓度在1014-1017cm-3;退火温度高于410℃时,随着退火温度的升高薄膜晶粒长大,结晶性增强,此时薄膜内部缺陷减少,载流子浓度升高;对于用作太阳电池吸收层的CIGS,从载流子浓度及迁移率的角度评判,合适的退火温度区间为450-550℃。

The as-deposited CuIn1-xGaxSe2(CIGS) thin films were fabricated by magnetron sputtering from a quaternary CIGS target, and then the as-deposited films were annealed in a temperature range from 240℃ to 550℃. The effect of the annealing temperature on the electric properties(carrier concentration and carrier mobility) of the films was investigated in particular. The results show that when the annealing temperature was lower than 270℃, the highly conducive CuSe phase existed in the films leading to a high carrier concentration(1017-1019cm-3) and a low carrier mobility(~0.1 cm2·V-1·s-1). These films are not suited for CIGS absorber usage. When the annealing temperature was higher than 410℃, the carrier mobility of the films was high about 10 cm2·V-1·s-1and the carrier concentration was in a range of 1014-1017cm-3due to the disappearance of the CuSe phase. When the annealing temperature was higher than 410℃,with the increase of the annealing temperature the grains grew larger and the crystallinity of the films was enhanced, which could reduce the defects in the films and result in the decrease of the carrier concentration. From the aspect of the carrier concentration and the carrier mobility, the appropriate annealing temperature for fabricating the absorbers of the CIGS solar cells is from 450℃ to 550℃.