Sulfur-Vacancy Passivation in Solution-Processed Sb₂S₃ Thin Films: Influence on Photovoltaic Interfaces

Abstract

We have presented a modified two-step sequential deposition method in forming Sb2S3 thin films. In contrast to conventional chemical bath deposition (CBD) route, this sequential deposition approach has allowed passivation of sulfur vacancies in Sb2S3 through a control over precursor stoichiometry (S/Sb ratio) during the film formation. We have made an in-depth characterization of the chalcogenide thin films upon passivation of the vacancies. While a sulfur-deficient composition led to the formation of donor-like sulfur vacancies, a sulfur-rich stoichiometry passivated such vacancies followed by creation of sulfur antisite defects in the chalcogenide. Scanning tunneling spectroscopy and thereby density of states allowed us to locate individual band-energies and their dependence on defect passivation. A strong dependence of optical bandgap and surface morphology of the Sb2S3 layer on the precursor stoichiometry was evidenced in our study, and an optimized balance between the parameters was estimated for a slightly sulfur-rich composition (S/Sb ratio of 1.2). Interestingly, the photovoltaic parameters of Cu:NiO/Sb2S3/PCBM planar heterojunctions excelled at the predicted stoichiometry, yielding a power conversion efficiency of 3.02% along with a significantly high open-circuit voltage of 0.8 V. This effort thus provides new insights into the influence of defect passivation on solar cell characteristics based on solution-processed Sb2S3 thin films.

High‐Efficiency Sb2(S,Se)3 Solar Cells with New Hole Transport Layer‐Free Back Architecture via 2D Titanium‐Carbide Mxene

“…Particularly, two dominant peaks at 281 and 309 cm −1 correspond to antisymmetric and symmetric stretching vibrations υ a and υ s (Sb–S), respectively. [ 51,52 ] A closer inspection of these two modes found that with MXene coupling, the intensity of peak corresponding to symmetric stretching (υ s ) gained its intensity. It indicates that there are fewer sulfur vacancies on Sb 2 (S,Se) 3 surface with MXene according to the previous defect study by Raman.…”

Doping Strategies in Sb2S3 Thin Films for Solar Cells

“…Most recently, Maiti et al. [ 79 ] developed a two‐step sequential deposition method for the synthesis of Sb 2 S 3 thin films using antimony acetate and thiourea (TU) as anionic and cationic precursors dissolved in DMF and DMSO, respectively, at 70 °C. To deposit Sb 2 S 3 films, the substrate was first spin coated with a cationic precursor, followed by an anionic precursor.…”

Defects and Their Passivation in Hybrid Halide Perovskites toward Solar Cell Applications

“…Interestingly, such defects can form even in high‐quality films, affecting the photovoltaic performance in an adverse manner. [ 30–32 ] Fortunately, as mentioned earlier, the prototype MAPbI 3 has shallow defect levels and can be considered to be a defect‐tolerant semiconductor. [ 50 ] This unique property of MAPbI 3 is beneficial in designing solar cell devices as the possibility of trap‐assisted recombination is low under this condition.…”

“…[ 27–29 ] In solar cell architectures, these defects act as recombination centers in the bulk of the material; in addition, grains and grain boundaries affect carrier transport adversely. [ 30–32 ] These intrinsic defects can moreover introduce a hysteresis (in the current–voltage characteristics), which remains another area of concern in terms of the reproducibility of device characteristics. [ 33–35 ]…”

“…[27][28][29] In solar cell architectures, these defects act as recombination centers in the bulk of the material; in addition, grains and grain boundaries affect carrier transport adversely. [30][31][32] These intrinsic defects can moreover introduce a hysteresis (in the current-voltage characteristics), which remains another area of concern in terms of the reproducibility of device characteristics. [33][34][35] Considering the significant influence of defects on light absorption, carrier extraction, and carrier transport in a hybrid halide perovskite-based device, it is hence essential to understand them as clearly as possible.…”