Efficient All-Printable Solid-State Dye-Sensitized Solar Cell Based on a Low-Resistivity Carbon Composite Counter Electrode and Highly Doped Hole Transport Material

Abstract

Monolithic device architectures provide a route to large-area mesoporous solar cell manufacture through scalable solution-processed fabrication. A limiting factor in device scale-up is availability of low-resistivity printable counter electrode materials and reliable doped charge transport materials. We report an efficient all-printable monolithic solid-state dye-sensitized solar cell (ss-DSC) based on a high-conductivity porous carbon counter electrode and a highly doped 2,2′,7,7′-tetrakis­(<i>N</i>,<i>N</i>-di-4-methoxy­phenyl­amino)-9,9′-spiro­bi­fluorene (spiro-OMeTAD) hole transport material (HTM). A review of current state-of-the-art printable porous counter electrodes in DSC literature was conducted and identified blends of graphite/carbon black as promising composites for high-conductivity electrodes. Direct ex situ oxidation of spiro-OMeTAD produced a stable HTM dopant, and its incorporation with one of the lowest-resistivity graphite/carbon black composite materials reported to date drastically decreases device series resistance, particularly that of the porous insulating spacer. Doping improved all performance parameters, and following optimization we demonstrate scaled-up 1.21 cm² (1.01 cm² masked) devices achieving a maximum efficiency of 3.34% (average, 3.05 ± 0.23%)