<p>Modern photovoltaic (PV) technologies continue to achieve remarkable gains in power conversion efficiency; however, their long-term operational stability remains a central bottleneck limiting large-scale deployment. Conventional approaches treat stress thermal cycling, moisture exposure, ion migration, and mechanical strain as purely detrimental factors that accelerate degradation. In contrast, emerging evidence reveals that certain PV materials and device architectures exhibit anti-fragile behavior: their performance, microstructural order, or defect landscape improves when exposed to controlled stress. This review provides the first comprehensive framework that unifies the concepts of fragility, robustness, self-healing, and anti-fragility within PV systems. Building on recent experimental and theoretical findings, we analyze the fundamental mechanisms through which external stimuli can reduce defect densities, enhance crystallinity, promote ionic reconfiguration, and activate reversible chemical bonding pathways. A detailed examination of diverse material classes including halide perovskites, metal oxides, MXenes, organic semiconductors, and quantum dot systems highlights how specific stress stimuli (light, heat, electrical bias, humidity, or strain) can be harnessed to induce beneficial structural and electronic transformations. We further evaluate anti-fragile device architectures that leverage interfacial engineering, dynamic defect equilibria, strain-adaptive contacts, and nano-interlayer design to convert stress into functional improvement rather than degradation. Finally, we outline advanced in-situ and operando characterization tools capable of capturing real-time recovery and enhancement processes, and we propose a forward-looking roadmap for integrating anti-fragility into next-generation PV design. This review positions anti-fragile photovoltaics as a transformative paradigm for achieving resilient, self-adaptive, and ultra-stable solar energy technologies.</p>