Unrevealing the interaction between O₂ molecules and poly(3-hexylthiophene-2,5-diyl) (P3HT)

Abstract

Stability of π-conjugated organic materials remains a critical issue for applications in which these materials and devices based on them are exposed to ambient conditions.

The Quest for Air Stability in Organic Semiconductors

“…For instance, in P3HT, the process of O 2 doping in the dark at atmospheric pressure takes several hours while exposure to 500–700 nm light dramatically accelerates the process, affording a rate with units of seconds . This highly efficient photoinduced electron transfer process from P3HT to O 2 leads to the formation of a partially reversible pair of [P3HT] + and [P3HT:O 2 ] − CT complex. , The CT complex causes photobleaching of the active layer and has been attributed to the loss of performance in P3HT:PCBM bulk heterojunction solar cells . Irreversible photochemical degradation was also found on P3HT with evidence of O 2 –* formation suggesting an electron transfer to molecular oxygen occurred, while another degradation mechanism involving formation of sulfoxide (SO) on the thiophene backbone was proposed .…”

Semiconducting Polymer Nanoporous Thin Films as a Tool to Regulate Intracellular ROS Balance in Endothelial Cells

“…Semiconducting polymers, which have been widely used for decades in optoelectronics, i.e. , organic photovoltaics, organic light-emitting diodes, or organic field-effect transistors, have found increasing interest in photo-actuated biophotonics. , Apart from their intrinsic conductivity and optical properties, the chemical versatility, biocompatibility, and flexibility of conjugated polymers make them ideal candidates to accomplish the multifunctional properties requested for cell–material interfaces and, in particular, for the control of localized photoelectrochemical reactions. , Poly­(3-hexylthiophene) (P3HT) is a p-type polymer with interesting optoelectronic properties that acts as an efficient and highly biocompatible phototransducer, able to trigger biological pathways relevant to cardiac repair with a minimally invasive and gene-less approach. , When used as a photocathode in an aqueous environment, oxygen is the main acceptor, and it generates H 2 O 2 and other intermediate ROS species on the semiconductor surface, which can act as chemical signals for the cellular environment. , Semiconducting polymer nanomaterials based on P3HT have been shown to interact functionally with living cells and generate ROS upon visible light irradiation to trigger intracellular calcium ion flux or induce redox signaling processes. − In particular, P3HT-based thin films exhibit a stable and efficient photocatalytic activity in aqueous environments, making them suitable as extracellular bio-photoelectrodes to induce redox signaling processes. − Even more importantly, the material does not show relevant, irreversible photodegradation effects over long-term in vitro and in vivo functionality and allows for precise, on-demand targeting of subcellular organelles. , …”