Comment on "Interface state recombination in organic solar cells"

TL;DR

This paper critiques a previous study claiming interface state recombination as the main loss in organic solar cells, showing that steady-state measurements are insufficient to identify the dominant recombination mechanism.

Contribution

The authors demonstrate through simulations that steady-state current-voltage data cannot reliably distinguish between different recombination processes in organic solar cells.

Findings

Steady-state measurements do not conclusively identify recombination mechanisms.

Monomolecular or bimolecular recombination cannot be inferred from photocurrent slopes.

The validity of mobility-lifetime product calculations from steady-state data is questioned.

Abstract

In a recent paper, Street et al. [Phys. Rev. B 81, 205307 (2010)] propose first order recombination due to interface states to be the dominant loss mechanism in organic bulk heterojunction solar cells, based on steady-state current--voltage characteristics. By applying macroscopic simulations, we found that under typical solar cell conditions, monomolecular or bimolecular recombination cannot be inferred from the slope of the light intensity dependent photocurrent. In addition, we discuss the validity of calculating a mobility--lifetime product from steady-state measurements. We conclude that the experimental technique applied by Street et al. is not sufficient to unambiguously determine the loss mechanism.