The study investigates the upper efficiency limit of Sb₂Se₃ solar cells, focusing on the role of point defects in limiting their performance. Using first-principles calculations, the researchers analyze the trap-limited conversion efficiency of Sb₂Se₃, identifying vacancies as the most critical recombination centers. They predict an upper efficiency limit of 25% under optimal growth conditions where charged vacancies are minimized. Oxygen passivation is shown to reduce the detrimental effects of Se vacancies, improving performance. The study also highlights the importance of defect characterization in understanding and optimizing solar cell performance. The results suggest that Sb₂Se₃ solar cells are limited by non-radiative recombination, particularly under extreme Sb-rich growth conditions. By optimizing growth conditions and using oxygen passivation, higher conversion efficiencies can be achieved. The study provides insights into the efficiency limits of Sb₂Se₃ solar cells and offers a pathway to achieve performance close to the thermodynamic limit. The research underscores the significance of understanding and controlling point defects in improving the performance of Sb₂Se₃ solar cells.The study investigates the upper efficiency limit of Sb₂Se₃ solar cells, focusing on the role of point defects in limiting their performance. Using first-principles calculations, the researchers analyze the trap-limited conversion efficiency of Sb₂Se₃, identifying vacancies as the most critical recombination centers. They predict an upper efficiency limit of 25% under optimal growth conditions where charged vacancies are minimized. Oxygen passivation is shown to reduce the detrimental effects of Se vacancies, improving performance. The study also highlights the importance of defect characterization in understanding and optimizing solar cell performance. The results suggest that Sb₂Se₃ solar cells are limited by non-radiative recombination, particularly under extreme Sb-rich growth conditions. By optimizing growth conditions and using oxygen passivation, higher conversion efficiencies can be achieved. The study provides insights into the efficiency limits of Sb₂Se₃ solar cells and offers a pathway to achieve performance close to the thermodynamic limit. The research underscores the significance of understanding and controlling point defects in improving the performance of Sb₂Se₃ solar cells.