Constant photocurrent method and time-of-flight measurements applied to polymer blends

The constant photocurrent method has been used for many years to study the sub-bandgap absorption coefficient of inorganic amorphous semiconductors such as amorphous silicon. In this paper CPM is applied to conjugated polymers and blends of polymers and fullerenes. More precisely the polymer MEH-PPV, the fullerene derivative PCBM and blends of MEH-PPV and PCBM have been studied. Because of the spectral dependency of the quantum yield for unblended polymers, extra measurements of photocurrent transients were made to scale the CPM results. The carrier mobility is measured through time-of-flight measurements.