# Transient photocurrent and optical absorption of disordered thin-film semiconductors: in-depth injection and nonlinear response

Source: [Transient photocurrent and optical absorption of disordered thin-film semiconductors: in-depth injection and nonlinear response](<https://www.sota2.com/research/paper/68fa43d11e209131ce90cc57>)

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Data updated: 2025-10-25T04:30:47.784Z

Authors: Kazuhiko Seki, Naoya Muramatsu, Tomoaki Miura, Tadaaki Ikoma

Published: 2023-02-19T09:26:24.000Z

## Abstract

The time-of-flight method is a fundamental approach for characterizing the transport properties of semiconductors. Recently, the transient photocurrent and optical absorption kinetics have been simultaneously measured for thin films; pulsed-light excitation of thin films should give rise to non-negligible in-depth carrier injection. Yet, the effects of in-depth carrier injection on the transient currents and optical absorption have not yet been elucidated theoretically. Here, by considering the in-depth carrier injection in simulations, we found a 1/t^{1-alpha/2} initial time (t) dependence rather than the conventional $1/t^{1-alpha}$ dependence under a weak external electric field, where alpha\<1 is the index of dispersive diffusion.The asymptotic transient currents are not influenced by the initial in-depth carrier injection and follow the conventional 1/t^{1+alpha} time dependence. We also present the relation between the field-dependent mobility coefficient and the diffusion coefficient when the transport is dispersive. The field dependence of the transport coefficients influences the transit time in the photocurrent kinetics dividing two power-law decay regimes. The classical Scher--Montroll theory predicts a\_1+a\_2=2 when the initial photocurrent decay is given by 1/t^{a\_1} and the asymptotic photocurrent decay is given by 1/t^{a\_2}. The results shed light on the interpretation of the power-law exponent of 1/t^{a\_1} when a\_1+a\_2neq 2.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2302.09517>)

[PDF](<https://arxiv.org/pdf/2302.09517.pdf>)