Linker Design for Molecular-Level Control at Semiconductor Interfaces

Emerging technologies for the conversion of solar energy to produce electricity and energy-rich chemicals (solar fuels) are based on systems that involve, as key components, interfaces between molecules that absorb sunlight (called chromophores), or photocatalysts, chemically bound to metal oxide semiconductors or electrodes. The exchange of charges and interactions between the molecule and the metal oxide, following light absorption, influence the efficiencies of the device and of the photocatalytic processes that lead to fuels. Our research program aims at controlling and understanding, through careful synthesis of the molecular component, the properties of this important interface. Additionally, the synthetic design that will be developed and the electronic processes that will be studied in this project can impact research in other fields where it is important to control light absorption and charge transfer at molecule/oxide semiconductor boundaries, including molecular electronics, sensors, and photonics. Our synthetic organic research program is well integrated in the community developing photocatalysts and photovoltaics, and this synergy is demonstrated by existing collaborations within the DOE Solar Photochemistry Program. The proposed research is based on three objectives, each supported by preliminary work, and takes results obtained during the prior funding period in new directions. Objective 1. Stacking and orientation control of polyaromatic hydrocarbons on surfaces. We will develop surface binding strategies that promote specific stacking and orientation arrangements of chromophores on inorganic semiconductors and electrodes that favor desired electronic interactions. Objective 2. Develop robust and tunable anchor groups for binding. We will develop and study tunable anchor groups for chromophore or catalyst attachment on semiconductors and electrodes. The objective is to achieve strong binding and inhibit unwanted electronic processes, ultimately developing interfaces that are suitable for use in operating solar devices. Objective 3. Influence intramolecular electron transfer pathways with infrared excitation. We will continue studying molecules especially designed to explore mid-infrared modulation of electron transfer. The main contributions of the proposed work are fundamental in nature but have practical implications for enabling new technologies in solar energy science, which requires a thorough understanding of mechanisms of charge carrier dynamics at the molecular level. The proposed research projects will train students in organic synthesis, photochemistry, and nanostructured hybrids characterization, with an emphasis on engaging traditionally underrepresented groups. The PIER plan outlines how the PI will leverage the programs aimed at the recruitment and retention of students that are available at Rutgers-Newark. The PIER activities address recruiting, retention, mentoring, and professional development.