The phenomenon in which organic luminophores show higher photoluminescence efficiency in the aggregated state than in solution is called aggregation-induced emission enhancement (AIEE). Some luminophores, e.g., diketopyrrolopyrrole -based and sulfonamide -based luminophores, only display enhanced emission upon entering the crystalline state. That is, these luminophores are said to exhibit crystallization-induced emission enhancement (CIEE). Luminophores such as noble metallic nanoclusters show higher photoluminescence efficiency in the aggregated state than homogenous dispersion in solution. This phenomenon is known as Aggregation-Induced Emission (AIE).