Perovskite photovoltaics is emerging as one of the most competitive solar technology due to its excellent optoelectronic property and low fabrication cost. The development of perovskite solar cell technologies toward higher power conversion efficiency (PCE) and longer lifetime requires delicate control over the perovskite film and the relevant interfaces, and deep understanding of defects. Two related aspects are discussed: 1) Develop liquid medium annealing process¹ and related chemical means that leads to the films with high crystallinity, less defects, desired stoichiometry, and overall film homogeneity, resulting in solar cells with PCE over 25% (a certified 24.9%); 2) Propose methods such as "redox ion pair" and "multiple non-covalent bond synergistic effect" to suppress defect pairs in a sustainable way^2,3, which greatly improved the long-term stability of perovskite solar cells for over 2000 h under the stressors, e.g. light, heat, and electricity. Corresponding degradation mechanism of hybrid perovskite films and devices under operational conditions are revealed on the molecular and atomic scales.