Quantifying charge carrier density in organic solar cells by differential charging techniques
- Resource Type
- article
- Authors
- Kyohei Nakano; Yujiao Chen; Keisuke Tajima
- Source
- AIP Advances, Vol 9, Iss 12, Pp 125205-125205-5 (2019)
- Subject
- Physics
QC1-999
- Language
- English
- ISSN
- 2158-3226
Accurate determination of charge carrier density in organic solar cells under light irradiation is essential because charge carrier density is directly related to the bimolecular recombination rate and open-circuit voltage of the cells. We investigate the robustness of transient photovoltage/current (TPV/C) and impedance spectroscopy (IS) to interference from the geometric capacitance of the cells (Cgeo) during quantification of the charge carrier density. TPV/C and IS accurately quantify the charge carrier density of bulk heterojunction cells with small Cgeo. For planar heterojunction cells with a larger Cgeo contribution, IS fails to separate the charge carriers in the organic layer from those in the electrodes. In contrast, TPV/C eliminates the effect of Cgeo and gives a reasonable estimation of the charge carrier density in the organic layer with the planar heterojunction, demonstrating that TPV/C is more robust than IS to interference from Cgeo of the cells.