Abstract
Lead-free copper(I) halides have been demonstrated to exhibit high photoluminescence quantum yields with high air and light stability, making them one of the most promising semiconductors for next-generation light-emitting diode devices. The low-dimensional structures and soft lattices of Cu(I) halides induce the formation of self-trapped excitons (STEs) to achieve broadband emissions with high quantum yields. Herein, the recent studies on the electronic and optical properties of Cu(I) halides (i.e., Cs3Cu2X5, CsCu2X3, and A(2)CuX(3), where A = K+ or Rb+, X = Cl-, Br-, or I-) are reviewed and particular emphasis is placed on the role of the dimensionality and the halide in governing the electronic and optical properties (e.g., emission color and photoluminescence efficiency) via STEs. Several optoelectronic applications of Cu(I) halides are also discussed. In the last section, perspectives and challenges for the future development of Cu(I) halides in both optoelectronic and photocatalytic applications are outlined.