Steady-state and transient photovoltage measurements answer complementary questions. SPV spectroscopy says whether a material separates charge and at which photon energies. TPV says how long that separation survives. A mechanism study that uses both can tell a complete story; one that uses either alone tells half of it.
SPV: spectral threshold (band gap), separation efficiency at each wavelength, charge migration direction (signal polarity), and the effect of modifications on all of the above. TPV: recombination lifetimes, the distribution of fast and slow components, and the effect of traps and junctions on carrier survival.
Start with SPV spectra to establish where the material separates charge. Then TPV at a wavelength of strong SPV response to characterize the separated state's lifetime. Then repeat both after each modification: dopant, heterojunction, cocatalyst. The pair of spectra and decay curves, before and after, is the mechanism evidence.
Raised SPV with unchanged TPV means more charge separates but recombines just as fast, perhaps a light-harvesting improvement. Unchanged SPV with longer TPV means the same amount separates but survives longer, a trap passivation or junction effect. The combination is far more diagnostic than either number alone.
The final link is activity: do the same samples under the same light show reaction rates that follow the SPV/TPV trends? When activity, separation and lifetime move together, the mechanistic story closes; when they diverge, the divergence itself is the finding.
Perfectlight's surface photovoltage systems provide both steady-state and transient modes on one platform; see mechanism research solutions.
