Holistic Approach to Low‐Dimensional Perovskite Enveloping of Internal Interfaces and Grain Boundaries in Perovskite Solar Cells

Abstract To elevate the performance and durability of perovskite solar cells, a holistic approach to mitigating defects throughout the device is essential. While advancements in refining top interfaces have been significant, the potential of stabilizing buried interfaces and grain boundaries has not been fully tapped. The research underscores the transformative impact of guanidine phosphate (GP), a chemical agent that converts surplus PbI 2 into a low‐dimensional perovskite, thus reinforcing the stability of both buried interfaces and grain boundaries. Employing GP on quantum dot tin dioxide (QD‐SnO 2 ) surfaces revealed an exceptional grain wrapping effect at these critical junctures, as revealed by high‐resolution transmission electron microscopy. This novel low‐dimensional perovskite enveloping strategy not only passivates the grain boundaries but also delays the cooling of hot carriers, thereby diminishing charge carrier recombination. This strategy exhibits an enhanced power conversion efficiency, rising from 23.16% to 24.55%. Moreover, the modified device sustains over 90% of their initial efficiency after 1000 h of maximum power point tracking under one sun illumination and maintain 90% efficiency after 1400 h in moderate humidity, all achieved without the encapsulation. This breakthrough points to a robust method for augmenting perovskite solar cell, promising a more durable, and efficient solar energy.