Organometallic Photovoltaics: A New and Versatile Approach for Harvesting Solar Energy Using Conjugated Polymetallaynes

Abstract

Energy remains one of the world's great challenges. Growing concerns about limited fossil fuel resources and the accumulation of CO(2) in the atmosphere from burning those fuels have stimulated tremendous academic and industrial interest. Researchers are focusing both on developing inexpensive renewable energy resources and on improving the technologies for energy conversion. Solar energy has the capacity to meet increasing global energy needs. Harvesting energy directly from sunlight using photovoltaic technology significantly reduces atmospheric emissions, avoiding the detrimental effects of these gases on the environment. Currently inorganic semiconductors dominate the solar cell production market, but these materials require high technology production and expensive materials, making electricity produced in this manner too costly to compete with conventional sources of electricity. Researchers have successfully fabricated efficient organic-based polymer solar cells (PSCs) as a lower cost alternative. Recently, metalated conjugated polymers have shown exceptional promise as donor materials in bulk-heterojunction solar cells and are emerging as viable alternatives to the all-organic congeners currently in use. Among these metalated conjugated polymers, soluble platinum(II)-containing poly(arylene ethynylene)s of variable bandgaps (∼1.4-3.0 eV) represent attractive candidates for a cost-effective, lightweight solar-energy conversion platform. This Account highlights and discusses the recent advances of this research frontier in organometallic photovoltaics. The emerging use of low-bandgap soluble platinum-acetylide polymers in PSCs offers a new and versatile strategy to capture sunlight for efficient solar power generation. Properties of these polyplatinynes--including their chemical structures, absorption coefficients, bandgaps, charge mobilities, accessibility of triplet excitons, molecular weights, and blend film morphologies--critically influence the device performance. Our group has developed a novel strategy that allows for tuning of the optical absorption and charge transport properties as well as the PSC efficiency of these metallopolyynes. The absorbance of these materials can also be tuned to traverse the near-visible and near-infrared spectral regions. Because of the diversity of transition metals available and chemical versatility of the central spacer unit, we anticipate that this class of materials could soon lead to exciting applications in next-generation PSCs and other electronic or photonic devices. Further research in this emerging field could spur new developments in the production of renewable energy.