Controlled synthesis of (: Hk 1) preferentially oriented Sb₂Se₃ rod arrays by co-evaporation for photovoltaic applications

In this paper, we propose that the microstructural control of (hk1) preferentially oriented Sb₂Se₃ films from flat films to rod arrays can improve their photovoltaic efficiency by maximizing the carrier transport characteristics. We found that, during co-evaporation, there is a narrow substrate temperature window where the Sb₂Se₃ rod array can be formed with an (hk1) preferred orientation, thus maximizing the carrier transport characteristics. The substrate-temperature-dependent morphology of the Sb₂Se₃ films can be explained by nucleation and growth theory and the terrace-ledge-kink model. Dramatic changes in the (hk0) and (hk1) texture coefficients occur at 315 °C, and the critical temperature for obtaining the (hk1) preferentially oriented Sb₂Se₃ film is a substrate temperature of 315 °C. On the basis of the observed variation in the film microstructure and texture coefficient, the optimum Sb₂Se₃ rod array having an (hk1) preferred orientation is formed in a narrow range of substrate temperatures. As a result, we obtained an optimized Sb₂Se₃ thin-film rod array that shows effective carrier transportation. Further, the optimum fill factor, short circuit current, open circuit voltage, and efficiency of the Sb₂Se₃ device were observed in the Sb₂Se₃ rod array having an (hk1) preferred orientation, and the enhanced carrier transport characteristics are the main reason for the improved device properties. These results show that controlling the microstructure of Sb₂Se₃ allows improvements in the efficiency of (hk1) preferentially oriented Sb₂Se₃ films.