Influence of the cooling rate on the electrical conductivity of coevaporated CuInS2 thin films

We investigated the influence of the cooling rate in a deposition process on the electrical conductivity σ of ${\mathrm{CuInS}}_2$ thin films for solar cells. In situ measurements were used in order to monitor the electrical conductivity of Cu-poor films during growth and cooldown. It is shown that the room-temperature electrical conductivity ${\sigma }_{\mathrm{RT}}$ depends significantly on the cooling rate of the film after deposition. ${\sigma }_{\mathrm{RT}}$ reaches ${\text{1×10}}^{\text{−3}}$ ${\mathrm{S\hspace{0.17em}cm}}^{\text{−1}}$ for a cooling rate of 2.0±0.2 $\mathrm{K}\hspace{0.17em}{\min }^{\text{−1}}$ whereas for abrupt cooling and higher cooling rates ${\sigma }_{\mathrm{RT}}$ is reduced to ${10}^{\text{−6}}$ and ${10}^{\text{−5}}$ ${\mathrm{S\hspace{0.17em}cm}}^{\text{−1}}$ , respectively.