Nanocrystal-assisted defect control in hybrid perovskite solar cells for improved photovoltaic performance

• CdSe/ZnS core–shell quantum dots (QDs) effectively reduce defect states in perovskite solar cells (PSCs). • QDs integrated into the anti-solvent process enhance crystallization, yielding compact, pinhole-free perovskite films. • QD incorporation leads to lower non-radiative recombination, improving charge transport and carrier lifetime. • Red-emitting QD (r-QD) modified PSCs achieve a record PCE of > 21 %, significantly higher than the 18.3 % of control devices. • QD-passivated PSCs maintain > 90 % efficiency after 600 h of continuous illumination under MPPT conditions. Organometallic halide perovskite solar cells (PSCs) have emerged as leading candidates for new-generation photovoltaics due to their exceptional power conversion efficiency (PCE) and superior optoelectronic properties, including long carrier lifetimes, extended diffusion lengths, and high absorption ability. However, defects at grain boundaries and surfaces act as non-radiative recombination centres, severely degrading device performance and stability. In this study, we introduce a quantum dot (QD)-assisted anti-solvent engineering strategy (AES) to regulate perovskite crystallization and minimize defect states. By incorporating various ratios (0.3, 0.6, and 0.9 mg/mL) of CdSe/ZnS core–shell QDs with green (g-QDs) and red (r-QDs) emission into the anti-solvent process, we achieve a compact, pinhole-free perovskite morphology with reduced trap-assisted recombination. As a result, r-QD-incorporated double-cation PSCs achieve a breakthrough PCE exceeding 21 %, outperforming the control devices (18.3 %). Furthermore, QD-passivated PSCs exhibit remarkable operational stability, retaining over 90 % of their initial performance over 600 h of light exposure under maximum power point tracking (MPPT) conditions. The obtained findings highlight the potential of QD-assisted passivation in mitigating critical limitations in PSC technology, paving the way for enhanced stability and long-term performance through advanced anti-solvent engineering.