Transient Photocurrent (TPC) Tutorial: Extracting carrier dynamics from time-resolved photocurrents

Introduction

Transient photocurrent (TPC) is a widely used technique for probing charge-carrier dynamics in solar cells. In a TPC experiment, the device is held under short-circuit conditions and illuminated with a short light pulse. The resulting current transient provides insight into how charges are extracted, how quickly they recombine, and whether transport is limited by mobility or traps.

In the simplest case, a fast photocurrent decay indicates efficient carrier extraction, while slower or multi-exponential decays suggest trapping or recombination bottlenecks. The characteristic time constants extracted from fitting the transient can be linked to carrier lifetimes, transport pathways, and even internal capacitances.

TPC complements JV, Suns–Voc, and Suns–Jsc measurements by adding a time-resolved dimension, allowing you to “look inside” how carriers move immediately after excitation. In this tutorial, you will configure and run a TPC simulation, generate a transient current trace, and learn how to interpret the key features.

Step 1: Making a new simulation

Start by opening the New simulation window. For this example, we use an organic P3HT:PCBM solar cell (??, ??). The TPC procedure, however, is general and can be applied to any perovskite or organic device. Save the project to disk before proceeding.

Step 2: Selecting the simulation mode

After saving, the main simulation window opens. Switch the simulator into TPC mode by selecting it from the Simulation type menu (??). When you run the simulation in this mode, it will generate a photocurrent transient in response to a light pulse.

To configure the TPC experiment, open the Editors ribbon and select TPC (not shown here). This opens the configuration window (??), where you can adjust the pulse width, pulse intensity, and the time resolution of the simulation. Short, high-intensity pulses emphasise recombination, while longer, weaker pulses highlight transport limits.

Step 3: Looking at the results

Once configured, return to the main window and click Play (or press F9). When the run completes, open the Output tab (??) and locate tpc.csv. This file contains the time-resolved photocurrent trace (??).

You have now run a TPC simulation and produced the characteristic photocurrent transient. The decay dynamics provide direct insight into how quickly charges are extracted, whether traps are present, and how transport limits performance. To gain deeper intuition, experiment with the simulation parameters: changing mobilities, trap densities, or recombination rates will strongly affect the shape of the transient.