Polaron Recombination in Pristine and Annealed Bulk Heterojunction Solar Cells

TL;DR

This study investigates the dominant polaron recombination mechanisms in pristine and annealed bulk heterojunction solar cells using photo-CELIV, revealing different temperature dependencies and recombination orders.

Contribution

It provides new insights into how annealing affects polaron recombination dynamics in organic solar cells.

Findings

Pristine samples show temperature-dependent bimolecular recombination rates.

Annealed samples exhibit third-order, nearly temperature-independent decay rates.

Recombination mechanisms differ significantly between pristine and annealed conditions.

Abstract

We determined the dominant polaron recombination loss mechanism in pristine and annealed polythiophene:fullerene blend solar cells by applying the photo-induced charge extraction by linearly increasing voltage (photo-CELIV) method in dependence on temperature. In pristine samples, we find a strongly temperature dependent bimolecular polaron recombination rate, which is reduced as compared to the Langevin theory. For the annealed sample, we observe a polaron decay rate which follows a third order of carrier concentration almost temperature independently.