Recently-explored top electrode materials for transparent organic solar cells

Transparent photovoltaics placed on the additional surface area of buildings, including windows and siding, have the potential to transform renewable energy generation. In contrast to their inorganic, silicon-based counterparts, organic solar cells (OSCs) have high absorption coefficients and can also be flexible, light-weight, and low-cost. However, the use of OSCs as transparent solar cells requires developing a compatible active material alongside a suitable top conductive electrode (TCE) that maintains both high transparency and low resistivity. This mini-review will explore materials for the TCE of organic solar cells, examining the properties, advantages, challenges, and recent progress of such electrodes in the last five years (2016–2020). The performance characteristics of these materials in transparent and semi-transparent organic solar cells, including power conversion efficiency, average visible transmittance, and color-rendering index are noted. The TCEs studied encompass transparent conductive oxides; carbon-based conductive polymers, graphene, and carbon nanotubes; metallic nanowires, nanomeshes, and nanogrids; in addition to ultrathin metals and composite electrodes. The investigation of these top conductive electrodes for transparent organic solar cells offers promise toward more versatile photovoltaics and thus a more sustainable energy future. •Evaluate top conductive electrode properties and relate to device performance.•Materials explored include conductive polymer, nanomaterials, and ultrathin metal.•Researching organic solar cells has led to considerate efficiencies and transmittance.