Abstract
Upon the addition of lithium salts to the hole-transporter matrix,
2
,
2
′
,
7
,
7
′
-tetrakis(
N
,
N
-di-
p
-methoxypheny-amine)-
9
,
9
′
-spirobifluorene (spiro-MeOTAD), the authors observe a 100-fold increase in conductivity through spiro-MeOTAD within a
Ti
O
2
mesoporous network. The authors demonstrate this to be a bulk effect and not due to improved injection at the electrodes. By testing "hole-only" diodes of pure spiro-MeOTAD and those doped with lithium salts, the authors calculate that the hole mobility increases from
1.6
×
10
−
4
to
1.6
×
10
−
3
cm
2
∕
V
s
. The authors discuss the possible mechanisms for this significant enhancement in charge mobility and its implication to the dye-sensitized solar cell operation.