Ultrafast photocurrent detection contradicts optical detection conclusions: Exciton diffusion contributes little to carbon nanotube device efficiency
- 1Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
- 2Department of Materials Science and Engineering, University of Wisconsin–Madison, Madison, WI 53706, USA
Abstract
Many conclusions about energy conversion in next-generation photovoltaic devices are gleaned indirectly from optical measurements of exciton dynamics, not directly from photocurrent itself. This method is problematic because optical measurements report on all excitons, not just productive ones. Using a new ultrafast photocurrent spectrometer, we compare exciton dynamics of semiconducting carbon nanotubes measured in films to those measured in devices using photoabsorption- and photocurrent-detected transient and two-dimensional spectroscopies. We find that photoabsorption detection greatly overestimates the importance of long-lived excitons for photovoltaic device performance. Excitons diffuse across nanotubes for picoseconds, but we find that the photocurrent is mostly created by excitons that diffuse little before dissociating at the electron transfer interface within 30 femtoseconds of being created. Thus, scientific conclusions reached from optical-only studies bear little importance to the performance of these devices, calling into question the processes thought critical for efficient photoconversion. This study points to the necessity for directly measuring photocurrent-generating exciton dynamics, not surmising them from optical spectroscopy alone.
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BibTeX
@article{faitz2026ultrafast,
title = {{Ultrafast photocurrent detection contradicts optical detection conclusions: Exciton diffusion contributes little to carbon nanotube device efficiency}},
author = {Zachary M. Faitz and Christopher J. Blackwell and Dasol Im and Abitha Dhavamani and Xingyu Shen and Michael Scott Arnold and Martin T. Zanni},
journal = {Science Advances},
year = {2026},
month = jul,
doi = {10.1126/sciadv.aec3186},
url = {https://doi.org/10.1126/sciadv.aec3186},
note = {CC BY},
}
RIS
TY - JOUR
TI - Ultrafast photocurrent detection contradicts optical detection conclusions: Exciton diffusion contributes little to carbon nanotube device efficiency
AU - Zachary M. Faitz
AU - Christopher J. Blackwell
AU - Dasol Im
AU - Abitha Dhavamani
AU - Xingyu Shen
AU - Michael Scott Arnold
AU - Martin T. Zanni
PY - 2026
DA - 2026/07/01
JO - Science Advances
DO - 10.1126/sciadv.aec3186
UR - https://doi.org/10.1126/sciadv.aec3186
AB - Many conclusions about energy conversion in next-generation photovoltaic devices are gleaned indirectly from optical measurements of exciton dynamics, not directly from photocurrent itself. This method is problematic because optical measurements report on all excitons, not just productive ones. Using a new ultrafast photocurrent spectrometer, we compare exciton dynamics of semiconducting carbon nanotubes measured in films to those measured in devices using photoabsorption- and photocurrent-detected transient and two-dimensional spectroscopies. We find that photoabsorption detection greatly overestimates the importance of long-lived excitons for photovoltaic device performance. Excitons diffuse across nanotubes for picoseconds, but we find that the photocurrent is mostly created by excitons that diffuse little before dissociating at the electron transfer interface within 30 femtoseconds of being created. Thus, scientific conclusions reached from optical-only studies bear little importance to the performance of these devices, calling into question the processes thought critical for efficient photoconversion. This study points to the necessity for directly measuring photocurrent-generating exciton dynamics, not surmising them from optical spectroscopy alone.
SN - 2375-2548
ER -