The role of grain growth in controlling the crystal orientation of Sb2S3 films for efficient solar cells

The orientation of antimony sulfide (Sb2S3) significantly affects the performance of Sb2S3 thin film solar cells owing to its intrinsic quasi-one-dimensional crystal structure. Producing a Sb2S3 film with a [hk1] orientation is theoretically favorable for solar cell performance. However, it is a challenge to prepare a [hk1]-orientated Sb2S3 film, because Sb2S3 is prone to grow parallel to the substrates along the [hk0] orientation according to the minimum energy principle. Herein, guided by grain growth theory, we successfully control the orientation of a Sb2S3 film via modulating the grain growth process. Highly [hk1]-oriented Sb2S3 films on an CdS substrate can be obtained if the grain grows according to the normal grain growth model. Consequently, a solar cell device based on [hk1]-oriented Sb2S3 achieves a power conversion efficiency of 6.82%, performing better than that based on [hk0]-oriented Sb2S3 (6.27%). This research provides a new and effective method for orientation control of Sb2S3 for pursuing high performance Sb2S3 thin film solar cells.