Unveiling photophysical properties and optimal behavior of organic semiconductor materials derived from Carica...

Organic semiconductor materials from natural extracts have attracted significant attention due to their sustainability and tunable optoelectronic properties. This study explores photophysical properties of Carica pubescens fruit and leaf extracts to evaluate their potential as organic semiconductor materials. UV-Vis absorption analysis shows that the fruit extract, with a dominant peak at 263 nm attributed to π-π* transitions of anthocyanins and flavonoids, possesses a wide optical band gap of approximately 3.58 eV, suggesting limited semiconducting relevance. In contrast, the leaf extract displays multiple absorption bands in the visible region (424, 464, 615, and 663 nm), corresponding to chlorophyll a, chlorophyll b, and carotenoids. The optical band gap of the leaf extract, determined to be about 1.82 eV, falls within the ideal range for organic optoelectronic devices. Photoluminescence (PL) and time-resolved photoluminescence (TRPL) analyses uncover two distinct emission peaks at approximately 675 nm and 728 nm. Photophysical responses were evaluated over a concentration range of 50 to 500 ppm. At an optimal concentration of 250 ppm, the leaf extract exhibits maximum PL intensity, extended exciton lifetimes, and behaviors consistent with a partial reduction of non-radiative recombination channels. Increasing the concentration beyond this point leads to significant quenching effects and shorter lifetimes. This behavior is primarily governed by a static quenching mechanism, resulting from reduced intermolecular distances and enhanced molecular aggregation, which facilitate exciton-exciton annihilation. Overall, the Carica pubescens leaf extract demonstrates tunable and optimum photophysical behavior at 250 ppm, indicating that it is a promising bio-derived organic semiconductor candidate from an optical standpoint for sustainable photovoltaics, biosensing, and flexible optoelectronics, pending future confirmation of its charge-transport properties in solid-state devices.