Sequential series multijunction dye-sensitized solar cells (SSM-DSCs): 4.7 volts from a single illuminated area†
Sequential series multijunction dye-sensitized solar cells (SSM-DSCs), which are mechanically stacked single illuminated area DSC devices wired in series, are reported to have exceptionally high photovoltages (Voc) ranging from 1.9–4.7 V from 2–5 stacked subcells. The use of multiple photoactive films under one area within the SSM-DSC framework is made possible by fine-tuning the thickness of TiO2 in each device and by judicious dye selection to allow for excellent light distribution among the films, termed as “photon management”. The SSM-DSC approach allows for incorporation of materials designed to use the maximal potential energy of photons in each region of the solar spectrum. Importantly, SSM-DSCs were observed to maintain high Voc under low-light conditions, rendering these systems very attractive for indoor applications. Additionally, an SSM-DSC was found to have a solar-to-fuel conversion efficiency of 2% (2.7% including H2 production) for the reduction of CO2 to CO with IrO2 and Au2O3 electrocatalysts, without an external bias.