Molecular/polymeric metallaynes and related molecules: Solar cell materials and devices

Energy remains one of the great challenges for the world. There is a considerable interest in developing renewable energy resources and improving the technologies for energy conversion. In this context, solar energy is a source with the proven capacity to meet the increasing global energy needs. In recent years, efficient organic solar cells (OSCs) have been fabricated using organic polymers and small molecules. Metalated conjugated organic molecules have also been shown to be good alternatives to the all-organic congeners and have demonstrated good promise as solar cell materials in OSCs and dye-sensitized solar cells (DSSCs). Among these, soluble molecular/polymeric metallaynes and their acetylide-functionalized metalloporphyrins show promising results in much of these investigations with the best power conversion efficiencies of 9.06% (for single-layer OSC), 12.5% (for tandem OSC) and 13.2% (for co-sensitized DSSC) to date. This review summarizes the recent advances of this field. Various factors influencing the device performance such as the nature of metal center and organic spacer, absorption coefficient, bandgap energy, charge carrier mobility, accessibility of triplet excitons and blend film morphology of these materials will be discussed. Given the diversity of transition metals available (for example, Pt, Zn, Ru) and structural versatility of the organic components, it is anticipated that this nascent field using metalated organic materials would continue to lead to exciting prospects in the near future.