Transient photovoltage (TPV) answers the question steady-state methods cannot: after the light goes off, how long do the separated charges survive? The photovoltage decay curve after a pulsed excitation maps recombination kinetics directly, making TPV a core measurement for photocatalyst and photovoltaic development.
A short light pulse creates carriers; the measurement tracks the surface photovoltage as it relaxes back to equilibrium. The decay reflects carriers recombining at surfaces, in the bulk and at traps. Longer decay tails mean longer-lived separated charge, which usually correlates with better photocatalytic performance.
Pulse width and energy must be weak-perturbation, the measurement should probe the system, not drive it into a different state. The detection bandwidth must be fast enough to capture the earliest decay component, and the repetition rate slow enough for full relaxation between pulses. Averaging many identical pulses raises signal-to-noise without changing the physics.
Decay curves are rarely single-exponential: they are sums of fast (surface) and slow (trap-limited or diffusion-limited) components. Fit with a purpose, use biexponential or stretched-exponential models only when a physical picture supports them, and compare fitted lifetimes only between materials measured identically.
TPV pairs naturally with transient photocurrent (the current analog of the same pulse experiment): photovoltage shows how long charge stays separated, photocurrent shows how much of it flows into the circuit. Together they separate storage losses from collection losses.
Perfectlight's SPV/TPV platforms integrate pulsed excitation and fast acquisition; see mechanism research solutions.
