Lead halide perovskite nanocrystals (LHP NCs) have emerged as next-generation semiconductor materials with outstanding optical and optoelectronic properties. Because of the high surface-to-volume ratio, the optical and optoelectronic performance and the colloidal stability of LHP NCs largely depend on their surface chemistry, especially the ligands and surface termination. On one hand, the capping ligands improve the colloidal stability and luminescence; on the other hand the highly dynamic binding nature of ligands is detrimental to the colloidal stability and photoluminescence of LHP NCs. In addition, the surface functionalization with desired molecules induces new functionalities such as chirality, light harvesting, and triplet sensitization through energy/electron transfer or use as X-ray detectors. In this review, we present the current understanding of an atomic view of the surface chemistry of colloidal LHP NCs, including crystal termination, vacancies, and different types of capping ligands. Furthermore, we discuss the ligand-induced functionalities, including photocatalysis and chirality.

Metal halides have been explored with the aid of strong photoluminescence for optical and optoelectronic applications. However, the preparation of lead (Pb)-free solid-state emitters with high photoluminescence quantum yields (PLQYs) and tunable emission remains exceptionally challenging. Herein, we report metal ion (Cu­(I), Mn­(II), and Sn­(II))-doped Cs3ZnI5 single crystals that are primary color (violet, green, and orange/red) emitters with extremely high PLQYs. Whereas the Mn-doping leads to bright green emissions with 100% PLQY, the Cu- and Sn-doping give rise to blue and red emissions with PLQYs of 57 and 64%, respectively. Interestingly, higher Mn doping results in white light emissive crystals as a side product, which are found to be Mn-doped CsI single crystals. The bright white light emissive crystals can be synthesized in a pure form in large quantities and exhibit a high color rendering index (CRI) of 78 and CIE coordinates of (0.30, 0.38), which are close to daylight conditions. To the best of our knowledge, this is the first demonstration of white light emission from a complete inorganic system. Importantly, the single crystals of all colors exhibit high long-term stability as their PLQY remains unchanged even after 2 months of preparation, and are thermally stable up to 600 °C.