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Elucidating mobile charge carriers in polymeric carbon nitrides by transient surface photovoltage analysis

Merschjann C, These A, Brabec C, Dittrich T, Jiménez Calvo P (2026)

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Publication Status: Submitted

Publication Type: Unpublished / Preprint

Future Publication Type: Journal article

Publication year: 2026

Original Authors: Christoph Merschjann, Albert These, Christoph Brabec, Thomas Dittrich, Pablo Jiménez Calvo

DOI: 10.26434/chemrxiv.15005627/v1

Abstract

Understanding charge carrier dynamics in granular photocatalysts is critical for rational materials design, yet conventional spectroscopies lack the spatial directionality needed to distinguish individual electron and hole contributions. Here, time-resolved surface photovoltage (TRSPV) spectroscopy is established as a contactless, carrier-resolved probe of charge transport in granular photoactive materials, using undoped and sulfur-doped polymeric carbon nitride (PCN) as model systems. A Marcus-Holstein small-polaron master-equation model is developed to simulate spatio-temporal carrier dynamics and calculate experimental observables, TRSPV, time-resolved photoluminescence (TRPL), and carrier mobility, within a unified framework. We show that SPV signals in centrosymmetric granular materials can be described by two physical mechanisms: dielectric screening and depth-dependent carrier photogeneration. Joint fitting of TRSPV and TRPL datasets reveals electrons as the more mobile carriers and holes as the least mobile in PCN, with free electron and hole polaron mobilities corresponding to site energies of 530 meV and 800 meV, respectively, and a combined hopping rate of the order of 1 ns-1. Trap-limited hole transport is further suppressed at defect sites, where bound polaron binding energies reach 340 meV in the bulk and 570 meV at surface sites. Sulfur doping and crystallite size modulate trap-state populations and transport timescales, with defect concentration governing the crossover between trap-limited and defect-band transport regimes. The spectroscopic methodology and theoretical framework presented here are material-agnostic and transferable to the broader class of granular photoactive absorbers, establishing TRSPV as a deployable diagnostic for photoelectrocatalysis research and solar energy conversion.

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How to cite

APA:

Merschjann, C., These, A., Brabec, C., Dittrich, T., & Jiménez Calvo, P. (2026). Elucidating mobile charge carriers in polymeric carbon nitrides by transient surface photovoltage analysis. (Unpublished, Submitted).

MLA:

Merschjann, Christoph, et al. Elucidating mobile charge carriers in polymeric carbon nitrides by transient surface photovoltage analysis. Unpublished, Submitted. 2026.

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