CdTe Quantum Dots Encapsulated on Perovskite Grains Enable Highly Efficient and Stable Perovskite Solar Cells

ABSTRACT Solution‐processed polycrystalline perovskites are inevitably endowed with inherent discontinuity at device heterointerfaces, which creates numerous interface segments that demand deliberate engineering of metastable interfacial configurations. Nevertheless, critical challenge remains in synchronously manipulating interfacial microscale carrier management while maintaining their microstructural integrity under operational stresses. Herein we demonstrate a strategy to fabricate localized microscopic p‐n heterointerfaces with high coherence and ionic bridging through encapsulating well‐defined p‐type CdTe quantum dots (QDs) on n‐type perovskite grains. Surface embeddings of such QDs establish unidirectionally aligned built‐in electric fields that facilitate directional carrier transport across micro‐heterointerfaces while expanding depletion regions to minimize recombination loss. Moreover, CdTe‐induced heteroepitaxial growth yields dislocation‐less interfaces between CdTe and perovskite, simultaneously passivating accessible defects of iodine vacancies and undercoordinated Pb 2+ at both the surface and grain boundaries, enabling high‐crystallinity perovskite films with robust microstructures. Given these striking merits, a record‐high efficiency of 26.73% (certified 26.02%) with a remarkable open‐circuit voltage of 1.222 V is achieved, setting a new performance benchmark among regular perovskite solar cells, along with pronounced operational stability with negligible efficiency degradation after nearly 700 h. This work pioneers a transformative laser‐mediated microscopic heterointerface engineering strategy that fundamentally reengineers microstructural carrier management and long‐term durability in advanced optoelectronics.