Oxygen doping of P3HT:PCBM blends: Influence on trap states, charge carrier mobility and solar cell performance

TL;DR

This study examines how oxygen exposure affects P3HT:PCBM solar cells, revealing increased charge carriers, deeper traps, and reduced mobility, which collectively influence device performance through experimental and simulation analyses.

Contribution

It provides new insights into the effects of oxygen on trap states, charge mobility, and device performance in P3HT:PCBM solar cells using combined experimental and simulation approaches.

Findings

Oxygen increases charge carrier concentration.

Oxygen exposure leads to deeper trap formation.

Charge mobility decreases with oxygen exposure.

Abstract

We investigated the influence of oxygen on the performance of P3HT:PCBM (poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester) solar cells by current--voltage, thermally stimulated current (TSC) and charge extraction by linearly increasing voltage (CELIV) measurement techniques. The exposure to oxygen leads to an enhanced charge carrier concentration and a decreased charge carrier mobility. Further, an enhanced formation of deeper traps was observed, although the overall density of traps was found to be unaffected upon oxygen exposure. With the aid of macroscopic simulations, based on solving the differential equation system of Poisson, continuity and drift-diffusion equations in one dimension, we demonstrate the influence of a reduced charge carrier mobility and an increased charge carrier density on the main solar cell parameters, consistent with experimental findings.