Steady-state photoconductivity and multi-particle interactions in rubrene single crystals

TL;DR

This study investigates the complex photoconductivity behavior of pristine rubrene crystals, revealing distinct regimes influenced by multi-particle interactions and surface effects, supported by a model involving exciton dynamics.

Contribution

It introduces a comprehensive model explaining the non-trivial photoconductivity regimes in rubrene crystals, emphasizing surface dominance and multi-particle exciton interactions.

Findings

Photocurrent exhibits power-law regimes with exponents 1, 1/3, and 1/4.

Surface photocurrent dominates over bulk response.

A model based on exciton fission, fusion, and triplet-charge quenching explains the observed phenomena.

Abstract

We demonstrate that photoconductivity of pristine rubrene crystals exhibits several distinct regimes, in which photocurrent as a function of cw (continuous wave) excitation intensity is described by a power law with exponents sequentially taking values 1, 1/3 and 1/4. We show that this photocurrent is generated almost exclusively at the surface of pristine rubrene crystals, while the bulk photocurrent is dramatically smaller and follows a different set of exponents, 1 and 1/2. A model based on exciton fission, fusion and triplet-charge quenching is developed to describe these non-trivial effects in photoconductivity of highly ordered organic semiconductors.