Analysis of Se Co-evaporation and Post-selenization for Sb₂Se₃-Based Solar Cells

Abstract

Sb2Se3 is a promising alternative absorber material for thin-film solar cells. However, by a thermal evaporation technique, it appears to partially decompose, leading to Se deficiency. In this work, we propose two alternative routes for the supply of selenium in the deposition of Sb2Se3 thin films. The first method is the co-evaporation of Se and Sb2Se3, while the second is the post-deposition selenization. Superstrate glass/FTO/TO/CdS/Sb2Se3/Au-configured thin-film cells are grown using thermal evaporation. X-ray diffraction patterns confirm the presence of CdS peaks along with the preferred (hk1) oriented grains, which are suppressed upon selenization. Modified surface morphology for the selenized samples is observed by atomic force microscopy. Enhanced current density is observed by J–V characterization and also confirmed by a remarkable external quantum efficiency (EQE) gain at long wavelengths. However, CdS deterioration reduces the EQE response in the short wavelength region, acting as a limiting factor for the efficiency improvement. The champion cell shows a power conversion efficiency of 3.6% with an open circuit voltage of 352 mV and a fill factor of 44.2%, which results in, to our knowledge, the highest value for thermally evaporated Sb2Se3 in superstrate configuration.

Theoretical studies on surface kinetics and growth properties of Sb2Se3 and Sb2S3

“…22,23 This kinetic origin could also probably explain why a conventional defect-engineering strategy like the post selenization process cannot signicantly reduce the defect density as expected. 22,27,45,46 Moreover, the Sb adatom prefers the pathway in the vdW gap to diffuse along the and [010] direction, respectively. This suggests an opposite diffusion anisotropy of Sb and S adatoms, similar to that on Sb 2 Se 3 (001).…”

Post deposition annealing effect on properties of CdS films and its impact on CdS/Sb2Se3 solar cells performance

“…Given that Sb-Se atoms form covalent bonds within ribbons, but adjacent ribbons only bond via weak van der Waals' forces, vertical (and vertically-tilted) Sb 2 Se 3 ribbons have been deemed optimal for efficient charge transport (Li K. et al, 2019;Hobson et al, 2020;Krautmann et al, 2021). Thus, substantial research efforts have been dedicated to the development of Sb 2 Se 3 absorber films, to deliver suitable processing conditions for optimal grain morphology and orientation [hkl, l = 1] and for efficient Sb 2 Se 3 solar cells (Kumar et al, 2021;Büttner et al, 2022;Campbell et al, 2022;Weiss et al, 2022). Another big focus in the development chain of Sb 2 Se 3 -based solar cells has been the identification of a suitable heterojunction partner layer to the Sb 2 Se 3 absorber, where various buffer layers, e.g., cadmium sulfide (CdS) (Weiss et al, 2022), titanium dioxide (TiO 2 ) (Phillips et al, 2019), zinc oxide (ZnO) (Wang et al, 2017), cadmium selenide (CdSe) (Guo et al, 2019), tin oxide (SnO 2 ) (Zhou et al, 2020) have already been tested.…”

Study of thermally evaporated Sb2Se3-based substrate-configured solar cell

“…Theoretical studies have predicted that the efficiency of Sb 2 Se 3 can be reached as high as 32% [9]. Apart from closed-space sublimation [2,[10][11][12], there are various techniques by which Sb 2 Se 3 TFSCs have been fabricated, such as thermal evaporation [13][14][15][16][17][18][19][20], e-beam evaporation [21,22], vapor transport method [23][24][25], rapid thermal evaporation [26,27], pulsed laser deposition [28], sputtering [29], solution-based methods [30], etc. In our earlier studies, we have grown Sb 2 Se 3 thin films by e-beam evaporation [31] and pulsed laser deposition [32] and studied its phase formation, optical and electrical properties.…”