Design and characterization of inorganic-organic interfaces for photovoltaic devices

• Grant number: 24/13458-0
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: June 01, 2025
• End date: September 30, 2028
• Field of knowledge: Physical Sciences and Mathematics - Physics - General Physics
• Principal Investigator: Thiago Branquinho de Queiroz
• Grantee: Leonardo Rodrigues Moreira
• Host Institution: Centro de Ciências Naturais e Humanas (CCNH). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
• Associated research grant: 20/13466-1 - Design, synthesis and characterization of molecular systems for light harvesting and charge separation, AP.JP

Abstract

Organic photovoltaic devices (OPVs) using bulk heterojunctions (BHJs) with low bandgap oligomers and polymers as donors (D) and non-fullerene acceptors (NFAs) have achieved impressive 15-20% of power conversion efficiencies (PCE) - particularly with NFAs of the Y6 family, composed by a D-A-D conjugated molecular systems with a S,N-heteroacene backbone. However, limitations remain due to thermal and exciton recombination losses, restricted electron and hole transport, and interface barriers. Additionally, electrode oxidation and photodegradation of active molecules reduce device's durability. To address these challenges, we propose strategies to tailor the work function of transparent electrodes and improve the chemical and electronic coupling at the interfaces. Indium tin oxide (ITO) and Fluorine-doped tin oxide (FTO) will be functionalized with self assembled monolayers (SAMs) composed of conjugated phosphonic acids designed by accurate quantum computational methods to act as collective polarized layers and step-through charge injection into the BHJ. Then, optimized BHJ films and OPV devices will be obtained. The structural properties will be characterized by X-ray photoelectron spectroscopy (XPS), solid state nuclear magnetic resonance spectroscopy (NMR) - performed in functionalized nanoparticles as model system -, atomic force microscopy (AFM) and photo-induced force infrared spectroscopy (PiF-IR), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The electronic properties as ionization energies and bandgap will be characterized by optical spectroscopy, Ultraviolet photoelectron Spectroscopy (UPS), XPS and Kelvin probe force microscopy (KPFM). Photo-electrical measurements and impedance spectroscopy as a function of temperature and working time will be used to characterize charge transport properties and durability. Through this comprehensive approach, we aim to gain a deeper understanding of photoinduced charge separation in these layered devices and pave a way for more durable and efficient OPV systems.