1 research outputs found
Cross-Linkable Molecular Hole-Transporting Semiconductor for Solid-State Dye-Sensitized Solar Cells
In this study, we investigate the
use of a cross-linkable organosilane semiconductor, 4,4′-bis[(<i>p</i>-trichlorosilylpropylphenyl)phenylamino]biphenyl (TPDSi<sub>2</sub>), as a hole-transporting material (HTM) for solid-state dye-sensitized
solar cells (ssDSSCs) using the standard amphiphilic Z907 dye which
is compatible with organic HTM deposition. The properties and performance
of the resulting cells are then compared and contrasted with the ones
based on poly(3-hexylthiophene) (P3HT), a conventional polymeric HTM,
but with rather limited pore-filling capacity. When processed under
N<sub>2</sub>, TPDSi<sub>2</sub> exhibits excellent infiltration into
the mesoporous TiO<sub>2</sub> layer and thus enables the fabrication
of relatively thick devices (∼5 μm) for efficient photon
harvesting. When exposed to ambient atmosphere (RH<sub>amb</sub> ∼
20%), TPDSi<sub>2</sub> readily undergoes cross-linking to afford
a rigid, thermally stable hole-transporting layer. In addition, the
effect of <i>tert</i>-butylpyridine (TBP) and lithium bis(trifluoromethylsulfonyl)imide
salt (Li-TFSI) additives on the electrochemical properties of these
HTMs is studied via a combination of cyclic voltammetry (CV) and ultraviolet
photoemission spectroscopy (UPS) measurements. The results demonstrate
that the additives significantly enhance the space charge limited
current (SCLC) mobilities for both the P3HT and TPDSi<sub>2</sub> HTMs
and induce a shift in the TPDSi<sub>2</sub> Fermi level, likely a
p-doping effect. These combined effects of improved charge transport
characteristics for the TPDSi<sub>2</sub> devices enhance the power
conversion efficiency (PCE) by more than 2-fold for ssDSSCs