Work

Rapid Ambient‐Pressure Annealing of Cu2ZnSnS4 Thin Films Synthesized by Chemical Bath Deposition for Photovoltaic Applications

Year: 2025

Type: article

Abstract: The synthesis of Cu2ZnSnS4 (CZTS) thin films using scalable, low‐cost methods is often hindered by the need for post‐deposition sulfurization using toxic H2S gas to form the kesterite phase. This step increases the process complexity and introduces environmental risks. In this study, it is demonstrated that a brief annealing step in nitrogen, conducted without any external sulfur source, is sufficient to convert chemical‐bath‐deposited SnS/CuS/ZnS stacks into CZTS. The films are deposited on FTO‐coated glass and annealed at 450 °C in a nitrogen glovebox for 0–4 min. Complete phase conversion is confirmed by X‐ray diffraction and Raman spectroscopy after 2 min, with optimal crystallinity at 3 min. Scanning electron microscopy reveals elongated grains and densification; UV–vis spectroscopy yields a direct bandgap of 1.58 eV; and electrical measurements show a peak conductivity of 2.77 (Ω·cm)−1. When integrated into Ag/CdS/CZTS/FTO solar cells, the 3 min annealed films deliver a ~15‐fold increase in short‐circuit current density (Jsc = 106.7 μA cm−2) and a power output of 6.21 μW cm−2 compared to as‐deposited devices. These findings establish a rapid, ambient‐pressure, and H2S‐free method for fabricating CZTS absorber layers. This approach eliminates a major processing hurdle and advances low‐toxicity, Earth‐abundant photovoltaic technologies.

Source: physica status solidi (a)

DOI: 10.1002/pssa.202500468