Photovoltaic Efficiency Enhancement through Highly Crystalline Antimony Selenide Interface Engineering

Antimony selenide (Sb2Se3) has emerged as a promising photoelectric material owing to its excellent material properties. The power conversion efficiency of Sb2Se3 thin-film solar cells has reached an impressive 10.57% within a decade. Despite rapid development, the efficiency of Sb2Se3 thin-film solar cells remains significantly below the theoretical prediction of 30%. Therefore, considerable efforts are still required to enhance the material quality of Sb2Se3, a critical factor in boosting solar cell efficiency. Post-deposition annealing treatments have been carried out as an effective method to improve the qualities of Sb2Se3 thin films, such as crystallinity and optical properties. However, these treatments typically require tens of minutes or more of thermal annealing at high temperatures (>300 °C), which severely limits both the throughput and substrate choice. For the first time, a low thermal budget annealing technique was used for post-deposition annealing of Sb2Se3, which was carried out to enhance the film properties of Sb2Se3 thin film solar cells. Photonic curing uses pulsed light annealing with a broadband light source and Sb2Se3 samples annealed with single pulse light in pulse lengths of 1 to 15 ms. This process heats the Sb2Se3 film above 400 °C within milliseconds without damaging the underlying layers of the material stack. Short pulses (less than 5 ms) having higher radiant power damage the Sb2Se3 thin films compared to longer pulses. In contrast, during longer pulses, the temperature rises quickly and decreases gradually, even while the light remains on. This is due to the power in the capacitor bank draining, which reduces the lamp’s output and limits the peak temperature at the sample surface. As a result, longer pulses cause less damage and lead to more crystalline films. Therefore, increasing pulse duration or reducing radiant exposure can minimise damage to the Sb2Se3 film. Photonic curing has increased the crystal orientations in the hkl, l ≠ 0 ([211] and ([221]) direction of Sb2Se3, reduced the surface roughness and decreased the leakage current of the solar cells. The reduced open circuit voltage effectively lowers recombination rates of charge carriers and improves carrier transport. These enhance the power conversion efficiency of Sb2Se3 by 46%. Hence, photonic curing shows the capability of curing Sb2Se3 thin films and creating high-quality Sb2Se3 thin films with high crystallinity without sacrificing surface coverage. This eliminates the rate-limiting annealing step and opens up new opportunities for Sb2Se3 photovoltaics.