Stability of CZTS thin film solar cells upon accelerated thermal cycling and damp heat exposure

Cu₂ZnSnS₄ (CZTS) thin film solar cells have attracted scientific and economic interest in the last decade. In this study, accelerated thermal cycling and damp heat tests are used to examine the stability of CZTS thin film solar cells, which are coated with two TCO materials. From the results, the CZTS solar cells with ZnO and ITO perform better durability than the one with ZnO and AZO under the accelerated thermal cycling test. The result also indicates that the ZnO and AZO deposited by using atomic layer deposition (ALD) technique does not improve the stability for CZTS solar cells comparing to the sputtering technique. In the damp heat experiment, the results show that the bare ITO thin films and AZO thin films deposited by the ALD technique have a good durability with regard to the moisture ingress. The AZO thin films deposited by RF sputtering without annealing have a worse performance with regard to electrical properties after the damp heat test. However, the cells with an ITO layer do not sustain a good performance after the damp heat test, which could be attributed smaller thickness of the ITO thin films. Although the AZO thin films using the ALD technique have better durability than the ones using the RF sputtering, the cells coated with the ZnO and AZO by the ALD technique are not much better than the cells coated with the ZnO and AZO by the RF sputtering.