Doping of organic semiconductors (OSCs) plays an important and growing role in organic electronics, ranging from OLEDs and OPVs to bioelectronics, and neuromorphic computing. However, unlike Si where parts per million dopant concentrations can significantly alter the conductivity, doping organic semiconductors with molecular dopants requires a much higher concentration (>5%), pointing to the fundamental bottlenecks in molecular doping of OSCs. Furthermore, the conductivity of doped OSCs deviates from the linear increase with doping concentration >20% (e.g., MeO-TPD doped with F4-TCNQ), or plateaus at low doping levels (e.g., 10% for P3HT doped with F4-TCNQ). This MURI team combines expertise in synthesis (You), characterization of materials (Ginger, So, Ade), novel device concepts and engineering (So), processing and morphological characterization (Amassian, Ade), computation (Li), robotic experimentation and ML data-analytics (Amassian, Ganapathysubramanian). This integrated team will address the fundamental questions outlined above, and explore novel photoredox dopant/switchable doping that can enable photopatterning of p and n doping to fabricate OSC integrated circuits. We will implement a collaborative workflow integrating robotic experimentation and machine learning (ML) to accelerate the pace of data generation, and co-design of dopant/polymers.

Hybrid materials incorporating both organic and inorganic components are being engineered to create new materials in which targeted optical and electronic properties are encoded through the control of nanoscale composition/morphology. Hybrid perovskites are a particularly exciting class of materials that have been realized as high-performance solar cells, light-emitting diodes, lasers, photodetectors and transistors. The crystalline nature of this hybrid family enables organic/inorganic functionalities combining essential attributes from the two distinct realms of chemistry. With the realization of the new optoelectronic technologies and the influence of the nanoscopic structure on desired macroscopic properties, there is a need to fully connect the structure and dynamics of the systems at a molecular level. In the proposed REU program, students will extensively utilize instruments and cutting edge analytical tools housed within facilities of the NSF-funded Research Triangle Nanotechnology Network (RTNN), which is one of 16 sites of the National Nanotechnology Coordinated Infrastructure (NNCI), and is a collaborative that partners North Carolina State University (NC State), the University of North Carolina at Chapel Hill (UNC-CH), and Duke University (Duke). Twelve undergraduate students annually will work in research labs at NC State, UNC, or Duke for 10 weeks during the summer. Through the collection and analysis of data, the students will elucidate new perspectives of hybrid perovskite systems and can directly apply this knowledge to the improvement of system designs and/or the investigation of novel applications. There are three objectives for this REU program: (1) To improve student knowledge of and provide hands-on experience for cutting-edge characterization techniques and analytical tools that can be used to evaluate hybrid perovskite systems; (2) to foster student interest in pursuing a career in STEM fields, especially those from underrepresented groups; and (3) to develop communication and networking skills in each of the participants.

We propose an Engineering Research Center for Green and Climate Resilient Built Environments (Green CriBs), which will drive innovation, engineering and widespread adoption of novel transparent envelope window and building materials to provide extreme thermal insulation together with dynamic and responsive light admittance for the built environment, its occupants and activities. Doing so will maximize the climate resilience of society, enhance environmental justice, reduce greenhouse gas emissions and accelerate grid decarbonization.

The aim of the proposed project is to identify and visualize the morphological and chemical origins of degradation in state-of-the-art organic photovoltaic (OPV) materials consisting of polymer donor and non-fullerene small-molecule acceptors (SMA). Specific objectives toward achieving this aim are as follows: (1) Visualize the multiphase morphology, associated heterointerfaces and energy landscape in modern bulk heterojunction (BHJ) OPVs utilizing emerging spectromicroscopic imaging based on scanning tunneling microscopy/spectroscopy (STM/STS) approaches. (2) Interrogate the relative morphological stability of phases and heterointerfaces under thermal, light and environmental stresses and aging. (3) Detect changes in energetic landscape, morphology and chemical degradation associated to burn-in or long-term aging using cross-sectional STM on actual OPV devices. (4) Propose new materials design guidelines, materials combinations, BHJ morphologies, and processing schemes which achieve maximum power conversion efficiency (PCE) while being thermodynamically and photochemically stable.

Base: The personnel at NCSU will provide complementary research to PolyPV LLC towards the goal of manufacturing flexible organic solar cell modules with high efficiency and lifetime. Specifically, multiple 1 cm2 cell that are to be connected into a module will be created by PolyPV LLC with scalable manufacturing methods such as blade-coating or slot-die printing. The subaward will characterize such devices for performance and stability and provide feedback to PolyPV LLC on how to improve the fabrication. NCSU will also provide benchmarking on devices produced by conventional spin-casting methods. Option: The type of characterization for the 6 month base-period and the 6 month option-period is essentially the same. The difference between these two periods is mostly in the devices produced by PolyPV LLC. We anticipate that during the 6 month option-period a new instrument that allows accelerated testing at high light intensity will become available.

This project aims to bridge the knowledge gap in the implementation of high-quality single crystal (SC) semiconductors into next-generation thin film-based electronic, optoelectronic and spintronic devices and their fabrication platforms. Specifically, we will focus on developing accelerated synthetic approaches which will enable SC growth on surfaces from a drying solution, their direct integration into electronic and optoelectronic devices, and ultimately the demonstration of wafer-scale SC device arrays. We will develop this in the context of hybrid metal halides (HMHs), an emerging salt-like class of semiconductors which have demonstrated remarkable semiconductor properties, ease of processing and a vast and yet unexplored chemical universe. Our approaches will enable the on-demand growth of semiconductor SCs with desired properties directly onto devices at designated locations using thin film deposition techniques, thus bringing about a paradigm shift in SC devices and ushering in a new era of accelerated co-design of SC materials and devices.

The objective of the proposed research is to address the NSF program call for ����������������low-cost, environmentally benign organic photovoltaics��������������� by rationally developing high throughput ambient printing of novel high efficiency semi-conducting polymer:non-fullerene based solar cells with active layers processed with (a) petrochemical solvents such as anisole and o-methylanisole that are safer and more benign than currently used chlorinated solvents, and (b) renewable, green solvents such as ethanol and possibly even water. The molecular design needed will be guided by fundamental molecular interaction considerations and detailed structure-solvent-morphology relations.

In this white paper we describe some of the fundamental questions that need to be answered in order to enable the fabrication of exceptionally stable tandems with greater than 30% efficiency. We will study perovskites with low, medium and high bandgaps. We have chosen to emphasize controlling stress and strain in perovskites because only a few manuscripts have been published on the subject despite the enormous importance it has been shown to have in the development of other thin-film electronic and optoelectronic devices. What causes strain buildup in solution-processed perovskite films must be understood at a fundamental level in order to develop stress mitigation strategies that are portable across materials (e.g., different bandgaps), processes (e.g., one-step vs two-step) and from lab-to-fab (e.g., spin-coating vs blade-coating). The need to control stress and strain is multiplied when dealing with tandem devices, which involve many more layers than a single junction device and two or more perovskite layers. We are also seeking to have a better understanding of what determines the density of halogen vacancies, since they are charged mobile defects that can both change the electric field in the device, trap charge and enhance recombination. It is very likely that stress and strain affect the density of vacancies

The proposed research program leverages expertise of an interdisciplinary group of scientists to develop fundamental synthesis-structure-property-function relationships for metal oxide nanomaterials for efficacy in inactivating surrogate viruses for COVID-19. The knowledge gained will enable accelerated and rational design of TiO2 nanoparticles for the production of specific reaction oxygen species that are important for the photodynamic inactivation of the COVID viruses. Such materials could be implemented into personal protective equipment and antiviral coatings.

The overarching goal of this research program is to develop an electronic structure to create high density of triplet excitons via singlet fission and transport these excitons over long distances and manipulate them for various functionalities. We will use a hybrid platform including molecular electronics to enable singlet fission to create triplet excitons, and organic/inorganic perovskites to transport these triplets across long distances into various potential centers to utilize these excitons in different processes.