Dye-sensitized nickel(II) oxide photocathodes for tandem solar cell applications

To date, nickel(II) oxide (NiO) is one of the few p-type semiconductors that has successfully been used for the construction of dye-sensitized photocathodes as well as tandem dye-sensitized solar cells. In this study we present a novel fabrication method for the preparation of mesoporous NiO films based on preformed NiO nanopowders. Critical properties such as pore-size distribution, crystallinity, and internal surface area of the resulting NiO films were controlled through the sintering process and optimized for their application as dye-sensitized photocathodes, resulting in a significantly increased photovoltaic performance, compared to earlier studies. A series of different sensitizers and electrolytes was scrutinized for their application in dye-sensitized NiO photocathodes. Despite its limited absorption range the dye coumarin 343 clearly outperforms other sensitizers used in this study. Values for short- circuit current densities of 2.13 mA cm(-2) and overall energy conversion efficiencies of 0.033% under simulated sunlight (AM1.5, 1000 W m(-2)) are the highest values reported in literature so far.