Highly effective carbon sphere counter electrodes based on different substrates for dye-sensitized solar cell

Recent progress on nanostructured carbon-based counter/back electrodes for high-performance dye-sensitized and perovskite solar cells

Dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) favor minimal environmental impact and low processing costs, factors that have prompted intensive research and development. In both cases, rare, expensive, and less stable metals (Pt and Au) are used as counter/back electrodes; this design increases the overall fabrication cost of commercial DSSC and PSC devices. Therefore, significant attempts have been made to identify possible substitutes. Carbon-based materials seem to be a favorable candidate for DSSCs and PSCs due to their excellent catalytic ability, easy scalability, low cost, and long-term stability. However, different carbon materials, including carbon black, graphene, and carbon nanotubes, among others, have distinct properties, which have a significant role in device efficiency. Herein, we summarize the recent advancement of carbon-based materials and review their synthetic approaches, structure-function relationship, surface modification, heteroatoms/metal/metal oxide incorporation, fabrication process of counter/back electrodes, and their effects on photovoltaic efficiency, based on previous studies. Finally, we highlight the advantages, disadvantages, and design criteria of carbon materials and fabrication challenges that inspire researchers to find low cost, efficient and stable counter/back electrodes for DSSCs and PSCs.

High-Performance Dye-Sensitized Solar Cells Based on Colloid-Solution Deposition Planarized Fluorine-Doped Tin Oxide Substrates

The transmittance and conductivity of fluorine-doped tin oxide (FTO) conductive glasses are the critical factors limiting the performance of dye-sensitized solar cells (DSSCs). Here, the transmittance and conductivity of commercial FTO glasses were improved via a colloid-solution deposition planarization (CSDP) process. The process includes two steps. First, the FTO nanocrystal colloid was deposited on the FTO glasses by spin-coating. Secondly, the coated glasses were treated by FTO precursor solution. Compared to the bare FTO glasses, the modified FTO glasses by the CSDP process achieved 4% increase in transmittance (at 550 nm) and 11% decrease in sheet resistance, respectively. In addition, the modified FTO glasses can reduce the aggregation of Pt nanoparticles and improve the electrocatalytic activity of Pt counter electrodes. When the modified FTO glasses were used to assemble DSSCs, the cells got a photoelectric conversion efficiency as high as 9.37%. In contrast, the efficiency of reference cells using bare FTO substrates was about 8.24%.