Interfacial Position Governs the Dual Functionality of Carbazole Layers in Cu2O Photocathodes

Abstract

Organic-inorganic hybrid photoelectrodes offer a promising strategy to improve charge separation in photoelectrochemical (PEC) systems, yet the influence of the spatial position of ultrathin organic interlayers remains poorly understood. Herein, we integrate electropolymerized carbazole-based conjugated porous polymers (CPPs) into Cu2O photocathodes by positioning the polymer either beneath or on top of the semiconductor. Both hybrid architectures exhibit en-hanced PEC performance compared with bare Cu2O, with the highest photocur-rent achieved when the polymer is deposited as an ultrathin overlayer. A combi-nation of electrochemical impedance spectroscopy together with femtosecond and nanosecond transient absorption spectroscopy reveals that the carbazole interlayer performs two distinct functions depending on its position within the hybrid architecture. When located beneath Cu2O, the polymer primarily facili-tates directional hole extraction and charge separation. In contrast, when depos-ited on top of Cu2O, the ultrathin polymer predominantly passivates surface defects, suppressing interfacial recombination and extending charge-carrier life-times while preserving efficient interfacial charge transfer. The triscarbazole-based polymer consistently exhibits slightly improved charge-transport proper-ties compared with its biscarbazole analogue. These findings demonstrate that the functionality of ultrathin organic interlayers is governed not only by their molecular structure but also by their spatial position within hybrid photoelec-trodes. More broadly, this work establishes interfacial positioning as a simple yet powerful design principle for engineering charge-carrier dynamics in organic-inorganic photoelectrochemical systemsgoes here.

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BibTeX RIS

BibTeX

@misc{garciaeguizabal2026interfacial,
  title = {{Interfacial Position Governs the Dual Functionality of Carbazole Layers in Cu2O Photocathodes}},
  author = {Alejandro García-Eguizábal and Miguel García-Tecedor and Miguel Gomez-Mendoza and Freddy Oropeza and Soranyel Gonzalez-Carrero and James R. Durrant and Marta Liras and Víctor A. de la Peña O’Shea and Mariam Barawi},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15008891/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008891/v1},
  note = {CC BY},
}

RIS

TY  - UNPB
TI  - Interfacial Position Governs the Dual Functionality of Carbazole Layers in Cu2O Photocathodes
AU  - Alejandro García-Eguizábal
AU  - Miguel García-Tecedor
AU  - Miguel Gomez-Mendoza
AU  - Freddy Oropeza
AU  - Soranyel Gonzalez-Carrero
AU  - James R. Durrant
AU  - Marta Liras
AU  - Víctor A. de la Peña O’Shea
AU  - Mariam Barawi
PY  - 2026
DA  - 2026/09/15
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15008891/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008891/v1
AB  - Organic-inorganic hybrid photoelectrodes offer a promising strategy to improve charge separation in photoelectrochemical (PEC) systems, yet the influence of the spatial position of ultrathin organic interlayers remains poorly understood. Herein, we integrate electropolymerized carbazole-based conjugated porous polymers (CPPs) into Cu2O photocathodes by positioning the polymer either beneath or on top of the semiconductor. Both hybrid architectures exhibit en-hanced PEC performance compared with bare Cu2O, with the highest photocur-rent achieved when the polymer is deposited as an ultrathin overlayer. A combi-nation of electrochemical impedance spectroscopy together with femtosecond and nanosecond transient absorption spectroscopy reveals that the carbazole interlayer performs two distinct functions depending on its position within the hybrid architecture. When located beneath Cu2O, the polymer primarily facili-tates directional hole extraction and charge separation. In contrast, when depos-ited on top of Cu2O, the ultrathin polymer predominantly passivates surface defects, suppressing interfacial recombination and extending charge-carrier life-times while preserving efficient interfacial charge transfer. The triscarbazole-based polymer consistently exhibits slightly improved charge-transport proper-ties compared with its biscarbazole analogue. These findings demonstrate that the functionality of ultrathin organic interlayers is governed not only by their molecular structure but also by their spatial position within hybrid photoelec-trodes. More broadly, this work establishes interfacial positioning as a simple yet powerful design principle for engineering charge-carrier dynamics in organic-inorganic photoelectrochemical systemsgoes here.
ER  -

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