Dynamic Characterization of Hybrid Solar Cells Based on Polymer and Aligned ZnO Nanorods by Intensity Modulated Photocurrent Spectroscopy

Abstract

For characterization of polymer-based solar cells with vertically aligned ZnO nanorod arrays (ZnO-NAs) by intensity modulated photocurrent spectroscopy (IMPS), a dynamic IMPS model is developed, where the structure-related charge generation and transport dynamics are considered. The model describes the IMPS responses affected by the phase shift ϕn(ω) due to the exciton diffusion property (ω0) and the structure-related device ideality factor N, the electron diffusion coefficient De, the exciton dissociation rate S, and the device structure (e.g., nanorod length d and interspacing l). The main expectations of the model are confirmed by the experimental data of the polymer/ZnO-NA cells with d = 180−650 nm, offering mechanistic information on the structure-related charge generation, charge transport, and device performance. The presence of the ϕn(ω) makes IMPS response not spiral into the origin and the phase angle in its Bode plot not tend to 90°; the d-dependent direct diffusion (DD) and diffusion-reflectio...