Photovoltage Bleaching in Bulk Heterojunction Solar Cells through Occupation of the Charge Transfer State

TL;DR

This paper investigates a charge transfer state in bulk heterojunction solar cells that causes photovoltage bleaching, revealing a new pathway for charge separation and photocurrent generation.

Contribution

It identifies a new peak in capacitive photocurrent linked to a charge transfer state, advancing understanding of charge dynamics in organic solar cells.

Findings

Peak in capacitive photocurrent below absorbance threshold

Illumination at peak energy blocks charge capture

Photovoltage drops significantly at the peak energy

Abstract

We observe a strong peak in the capacitive photocurrent of a MDMO-PPV / PCBM bulk heterojunction solar cell for excitation below the absorbance threshold energy. Illumination at the peak energy blocks charge capture at other wavelengths, and causes the photovoltage to drop dramatically. These results suggest that the new peak is due to a charge transfer state, which provides a pathway for charge separation and photocurrent generation in the solar cell.