Ligand‐Mediated Revival of Degraded α‐CsPbI3 to Stable Highly Luminescent Perovskite

After ageing under ambient conditions, the photoluminescence quantum yield (PLQY) of as-synthesized CsPbI₃ nanocrystals drastically declined to ≈11 % due to the formation of surface defect states. These “optically sick” CsPbI₃ nanocrystals are then revived to their cubic phase through the addition of 1-dodecanethiol (DSH), and regain a PLQY of approximately 90 %.

Abstract

Although α-CsPbI₃ is regarded as an attractive optical luminophore, it is readily degraded to the optically inactive δ-phase under ambient conditions. Here, we present a simple approach to revive degraded (“optically sick”) α-CsPbI₃ through “medication” with thiol-containing ligands. The effect of different types of thiols is systematically studied through optical spectroscopy. The structural reconstruction of degraded α-CsPbI₃ nanocrystals to cubic crystals in the presence of thiol-containing ligands is visualized through high-resolution transmission electron microscopy and supported by X-ray diffraction analysis. We found that 1-dodecanethiol (DSH) effectively revives degraded CsPbI₃ and results in high immunity towards moisture and oxygen, hitherto unreported. DSH facilitates the passivation of surface defects and etching of degraded Cs₄PbI₆ phase, thus reverting them back to the cubic CsPbI₃ phase, leading to enhanced PL and environmental stability.

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