Conjugated polymers and nature-derived molecules for light-emitting electrochemical cells and acidochromism

Licentiate thesis, 2024

Organic electronics have been dynamically developing in the last decades, garnering attention both within academia and industry for a variety of applications. Two of them are the focus of this thesis: light-emitting electrochemical cells (LEC) and acidochromic sensors. LECs are one step closer to delivering affordable and easily processed organic lighting technology promised by the OLED community. They rely on in-situ doping of the active
material for efficient charge transport. Given the increased efforts to switch to sustainable feedstocks, natural pigments are an appealing choice for LEC emitters. However, their commercial availability is often limited. In this work, a method of efficient isolation of chlorophyll a from spinach on larger scale was developed leading to the fabrication of the first chlorophyll-based LEC reported.
The second part of thiswork is dedicated to acidochromic materials. Conjugated polymers exhibiting changes in optoelectronic properties in the presence of trifluoroacetic acid were synthesised. Characterisation of the acidochromic behaviour combined with DFT calculations provided insight into the mechanism of acidochromic response for azo-, imine- and vinyl-bond-containing polymers. An exceptionally large bathochromic shift of 510 nm in
absorption was observed for the azo-containing polymer, which was attributed to very extensive planarisation of the polymer backbone.