Recent progress in organic-metal complexes for organic photovoltaic applications

Organic-metal complexes (OMCs) combine the functions of metals with mechanical properties and organic molecules with solution-processing properties, endowing them with the valence change characteristics of metal ions and diversity of organic molecular structures. Moreover, the coordination mode between the metal cations and organic ligands is flexible, enabling the application of OMCs in a wide variety of low-cost electronic and optoelectronic devices. As an important field of optoelectronic research, the applications of OMCs such as phthalocyanine-, porphyrin-, platinum- and ruthenium-based metal complexes in organic photovoltaic solar cells (OSCs) as the active layer, transport layer and additives are reviewed. The performance enhancements in OSCs are closely related to the structures and properties of OMCs. Herein, we provide an in-depth analysis of the structure-performance relationships of OMCs. Finally, perspectives on the opportunities and challenges of these materials are given. It is hoped that this review will inspire the development of OMCs for advanced OSCs.