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. 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.AVTaverage visible transmittanceOSCorganic solar cellsPCEpower conversion efficiencyTCEtransparent conductive electrodeTSCtransparent solar cellsOrganic solar cellsTransparent solar cellsTransparent conductive electrodeGrapheneCarbon nanotubesMetallic nanowiresA continuous 173,000 terawatts of solar energy strikes the Earth's surface, 10,000 times greater than worldwide energy consumption. Currently, the installed area of “terrestrial photovoltaics,” including rooftop solar panels, only suffices ~ 1% of global energy demand – there is therefore great potential to obtain energy from the sun, and the ability to generate electricity where we need it significantly reduces electrical losses and storage capacity needs. It is estimated that rooftop photovoltaics can comprise nearly 40% of the total electricity generation in the United States. Additional surfaces on and around buildings, such as windows and siding, could more than double the current photovoltaic surface area, representing a promising opportunity to help humanity attain net-zero energy consumption.To install solar cells on windows, the photovoltaic device must be semi- or fully transparent. An average visible transmittance (AVT) of 25% is a general benchmark in order for colorless, semi-transparent polymer solar cells to be used in window applications. Ideally, transparent solar cells (TSC) selectively absorb in the ultraviolet (< 435 nm) and near-infrared (> 670 nm) wavelengths while transmitting in the visible, allowing for transparency and hence greater versatility. Transparent photovoltaics have many applications, including electronic displays, foldable curtains, photovoltaic vehicles, building-integrate.
