# Substrate-Dependent Performance of ZnTTBPc–PMMA Composite Films on Rigid, Flexible, and Sustainable Materials for Wearable Devices

## TL;DR

This paper explores how different substrates affect the performance of ZnTTBPc-PMMA composite films for wearable devices, focusing on their structural and optical properties.

## Contribution

The study introduces innovative substrates like palm leaves and polyester for ZnTTBPc-PMMA composite films and evaluates their performance in wearable electronics.

## Key findings

- Films on palm leaves showed the highest fluorescence intensity and reflectance.
- Polyester fabric films exhibited the lowest optical band gap.
- Substrate morphology and drying dynamics significantly influence film structure and optical properties.

## Abstract

The purpose of this work is to evaluate the potential use of zinc 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (ZnTTBPc) embedded in polymethyl methacrylate (PMMA) and deposited on different substrates in active films for wearable device (WD) applications. The inclusion of PMMA as a matrix facilitates the incorporation of ZnTTBPc. The composite films were deposited by drop casting on PET, glass, and n-type silicon, as well as on innovative substrates, such as palm leaves and polyester. Regarding the composite films, surface analysis using SEM and AFM revealed substrate-dependent differences in film roughness, grain distribution, and crack formation, highlighting the influence of substrate morphology and drying dynamics on the structural integrity of the composite films. With respect to fluorescent and optical behavior, the highest fluorescence intensity (2573) and reflectance (75%) were obtained for the film deposited on palm, while the lowest optical band gap (1.52 eV) was found in the film on polyester fabric. Substrate–film interactions and deposition dynamics play a critical role in determining the structural integrity and topography of composite films, which, in turn, influence optical properties, fluorescence, and band gap. The multifaceted properties of all tested systems with the film structure, substrate/ZnTTBPc–PMMA suggest new possibilities for wearable electronics applications.