Structural and morphological properties of PLD Sb2Se3 thin films for use in solar cells

Sb2Se3 has been promising absorber layer for photovoltaics application because of its high absorption coefficient, optimal bandgap, non-toxicity with earth-abundant components. However, the control of Sb2Se3 absorber orientation is not fully achieved, although the importance of this issue had been realized in early studies. Whereas (hkl, l ≠ 0) crystal orientations of Sb2Se3 are favorable for photovoltaic absorber. In this work, pulsed-laser deposition (PLD) has been used to systematically investigate the correlation between the growth parameters and crystallographic orientation of Sb2Se3 thin films. Unlike literature reports, it has been shown that not only growth temperature, but also background pressure and/or selenium pressure should be considered to grow Sb2Se3 thin films with preferential crystallographic orientations. Independent of the substrate temperature between room temperature and 400 °C, Sb2Se3 thin films tend to grow along (hkl, l = 0) crystal orientations under vacuum. These peaks were also dominant in post-annealed samples under both Ar and N2 atmosphere at 400 °C. On the other hand, Sb2Se3 thin films with (hkl, l ≠ 0) crystal orientations were successfully deposited by introducing the Ar partial pressure and changing the Sb:Se ratio in the target. It has been demonstrated that not only growth temperature, but also background pressure and Se content in the target (or Se vapor pressure) have strong influence on the formation of Sb2Se3 thin film with desired crystallographic orientations. We anticipate that this work could accelerate further optimization of material properties for high efficiency photovoltaic cells.