Molecular Design and Development of Charge-Transporting and Interfacial Materials for Advanced Photovoltaic Applications

Project Overview

Emerging photovoltaic (PV) technologies, such as halide perovskite solar cells (PSCs) and organic photovoltaics (OPVs), are currently the focus of intense research. PSCs offer a unique combination of advantages for large-scale production and applications, including solution processability, diverse material and device engineering possibilities, and the ability to fabricate lightweight, flexible, and stretchable devices. Over the past five years, PSCs have achieved remarkable progress in device efficiency, with single-junction cells exceeding 27%.

In these multi-layered devices (Figure 1), light absorption and exciton generation occur in the perovskite layer. Photo-generated holes and electrons are extracted at the interfaces between the charge-transporting and active layers and are transported by the hole-transporting layer (HTL) and electron-transporting layer (ETL), respectively, toward the corresponding electrodes. These interfaces are as crucial as the photoactive component for ensuring optimal device operation and long-term stability. While much research has focused on the development of the perovskite layer itself, our project is dedicated to the design and development of organic hole-transporting materials (HTMs) and interfacial layers (see Figure 1). Both π-conjugated polymeric and small-molecule HTMs have been widely reported. Polymeric HTMs offer good mechanical and charge transport properties but often lack synthetic reproducibility. Small molecules, on the other hand, have well-defined molecular structures and are easy to synthesize and process, but typically suffer from lower charge mobility and a tendency to crystallize, which negatively affects film morphology. Molecular interfacial modifiers have also been developed to improve the perovskite/HTL interface, enhancing both efficiency and stability. The interfacial materials should have strong perovskite passivating capacity and efficient interaction with the HTM layer. However, even with reported HTMs exhibiting passivating effects, their device efficiencies still fall short of those using Spiro-OMeTAD. In this project, we propose to develop multifunctional materials that serve both as hole-extraction and transport layers and as passivation agents for the perovskite surface. These materials will combine the advantages of both polymeric and small-molecule systems, offering excellent morphological and mechanical properties, along with self-healing capabilities at low temperatures (within solar cell operating conditions), ensuring an optimal perovskite/HTL interface. The impact of the best-performing HTMs on device efficiency and long-term stability will be thoroughly investigated in collaboration with Prof. Thierry Pauporté’s team at IRCP Chimie ParisTech (https://www.pauportegroup.com). The project encompasses molecular design and synthesis, structural analysis, materials formulation and characterization (optical, electrochemical, photophysical, electrical, morphological properties), with applications in PSC devices.

Key Research Areas

• Organic and hybrid photovoltaics
• Charge-transporting materials
• Interfacial engineering
• π-Conjugated systems
• Molecular synthesis and characterization

Recent Related Publications from the Host Team:

• ACS Energy Lett. 2023, 8, 2267
• J. Mater Sci: Mater. Electron. 2022, 33, 17773
• Adv. Mater. 2021, 33, 2007431
• J. Mater Sci: Mater. Electron. 2021, 32, 12856
• Energies 2020, 13, 2897
• J. Mater Sci. 2020, 55, 4820
• Org. Electron. 2018, 60, 22
• J. Phys. Chem. C 2018, 122, 11651
• Chem. Asian J. 2018, 13, 1302

Situé sur le site de Neuville-sur-Oise, le Laboratoire de Physicochimie des Polymères et des Interfaces (LPPI) regroupe une vingtaine d’enseignants-chercheurs de diverses spécialités scientifiques (polyméristes, électrochimistes, chimistes inorganiciens, physiciens des surfaces et interfaces,…), 5 membres permanents administratifs et techniques et une trentaine de membres non-permanents (post-doctorants, doctorants, …).
Fort de cette pluridisciplinarité, le LPPI développe des thématiques de recherche concernant les matériaux polymères à architecture contrôlée, les matériaux polymères conducteurs ioniques et les matériaux (macro)moléculaires semi-conducteurs et conducteurs électroniques et leur modélisation.

Applicants must hold a Master's degree (or equivalent) in chemistry, polymer science, or materials science before the starting date. The candidate should demonstrate a strong interest in multidisciplinary research. Solid knowledge of molecular chemistry and π-conjugated materials is expected, and experience in organic electronics or organic semiconductors will be a strong asset. The ideal candidate will demonstrate a strong motivation to address challenges in renewable energy, with a particular focus on organic and hybrid photovoltaics. They are expected to quickly develop autonomy and proficiency in a chemistry laboratory setting. Strong oral and written communication skills in English or French are essential.