Experimental and simulation studies of transient photocurrent in organic solar cells

Transient photocurrent (TPC) is an important characterization technique to understand the carrier sweep-out, extraction and loss mechanisms in various types of solar cells. TPC is usually performed by illuminating a very short laser pulse onto a solar cell and studying its subsequent time-resolved photocurrent decay using an oscilloscope. In this work, we have built and tested an experimental setup to perform TPC measurements on a commercially available organic solar cell (OSC) under different applied voltage biases. The experimental results showed a decrease of the carrier sweep-out time as the internal voltage increased, which is consistent with the carrier sweep-out mechanism. Distinct carrier sweep-out times of the fast and slow carriers were extracted graphically, while linear fitting on the linear regime of the sweep-out time vs. the inverse of the internal voltage was adopted to estimate the electron and hole mobilities of the OSC. We further utilized General Purpose Photovoltaic Device Module (GPVDM) to simulate the TPC response in a similar OSC model. By back fitting our simulation to the experimental data, we were able to validate our experimental setup by matching the simulated and experimental TPC response and carrier mobilities in OSCs.