SPV and TPV produce curves; mechanisms are built from them by reasoning. The reasoning has rules, and it has traps. This guide walks the path from raw features to defensible mechanistic statements.
The onset wavelength locates the separation threshold, usually near the band gap but shifted by traps or junctions. The signal polarity states the migration direction of the majority carrier, toward or away from the surface. Sub-gap features point to defect or interface states; their strength relative to the band-to-band signal quantifies how much charge moves through traps instead of the band.
Fast components correspond to surface and near-surface recombination; slow tails to trap-limited or diffusion-limited processes. Modifications that extend the slow component without raising the fast one usually passivate traps; modifications that speed everything up usually add recombination centers. Compare only identically measured samples.
Assemble the argument in order: where does charge separate (SPV spectrum), which way does it go (polarity), how long does it last (TPV), and what changed with each modification (differences). A mechanism is the story that connects all four consistently. Any modification story should predict the next experiment, and state what result would refute it.
Over-reading signal magnitude without absorption normalization; assigning polarity without checking the geometry; fitting lifetimes with unphysical models; and building mechanisms from single measurements. The countermeasure for all four is the same, replicate, normalize, and predict.
Perfectlight's SPV/TPV platforms are built for reproducible mechanism work; see mechanism research solutions.
