  We report on the effect of the strong spin orbit coupling and the Lorentz
force on the efficiency of TiO2 based dye sensitized solar cells. Upon
inclusion of Ho2O3, due to the strong spin orbit coupling of the rare earth
Ho3+ ion, we do see 13 percent enhancement in the efficiency. We attribute such
an enhancement in power conversion efficiency to the increased lifetime of the
photo-excited excitons. Essentially, a Ho3+ ion accelerates the phenomenon of
the spin rephasing or the intersystem crossing of the excitons in a
photosensitizer. Increase in the absorbance and decrease in the
photoluminescence intensity suggests a decrease in the recombination rate,
hinting an enhanced charge transport and is in accordance with our
electrochemical impedance spectra and the J V characteristics. From the above
we strongly believe that enhanced efficiency of the device is due to increased
intersystem crossing which would accelerate the exciton dissociation. On top of
spin orbit interaction, a configuration where the electric and magnetic fields
are perpendicular to each other helped in enhancing the efficiency by 16
percent, suggesting that the Lorentz force also plays a dominant role in
controlling the charge transport of the photo-generated charge carriers. We
strongly believe that this simple and novel strategy of improving the
efficiency may pave the way for realizing higher efficiency dye sensitized
solar cells.
