Organic photovoltaic (OPV) technology can be a game-changer that allows simultaneous plant growth and power generation through precise sunlight spectral management in greenhouses, achieved through material selection and device design. PolyPV LLC and NCSU partners will develop flexible, wavelength-selective, semitransparent OPV modules that can be integrated with greenhouses making the greenhouses energetically independent without negatively impacting crop yield. The primary technical objectives and work at NCSU are to benchmark and characterize the following basic processes and their impact on performance using spin-coated, small research devices: 1. Develop processes to deposit transparent conductive electrodes from solutions 2. Develop OPV inks that contain transparent fillers that allow physically thick coatings of active layers with a large processing window that are ����������������optically thin���������������. 3. Develop and deploy transparent and flexible encapsulation.

The objective of Thrust II research is to unravel morphological origins of break-in losses and long term instability by developing a complete framework that allows to predict the long-term morphological stability of organic photovoltaic (OPV) cells based on measured physical properties (����������� parameter, glass transition temperature, molecular diffusivity) of the constituent materials. This thrust will develop general guidelines using model nonfullerene acceptor (NFA) based systems including those with >15% efficiency and screen potential polymer:NFA pairs for high-efficiency OPVs with practical operating lifetimes >10 years. The long-term goal is to achieve predictive structure-function relations that are also informed by the results from Thrust III and IV that can guide development of novel materials (Thrust I).

This proposal will develop the first semi-transparent 3-dimensional (3D) volumetric imaging array by leveraging the unique advantages offered by emerging organic photovoltaic (OPV) detectors. These new detector-based degrees of freedom will enable an extra dimension onto which information can be modulated, enabling more compact, robust, and capable optical imaging sensors and systems. Organic semiconductors are advantageous to realize this concept due to their ability to tune transmittance, polarization sensitivity, and spectral response, enabling detector placement arbitrarily within a lens system������������������s focal volume. These new degrees of freedom will be used to investigate new detector capabilities, optical systems, and image processing algorithms. The objectives of this proposal are to: (1) Establish an optical model of both 2D and 3D polarization sensitive organic photodetector (P-OPD) arrays; (2) Design a proof of concept 2D and 3D P-OPD arrays and readout circuitry; (3) Leverage the model to optimize spectral- and polarimetric- imaging array using birefringent filtering techniques; (4) Create algorithms for image reconstruction and calibration; and (5) Incorporate methods to create multi-layer volumetric 3D P-OPD arrays with liquid crystal layers.

The overarching goal of this project is to fabricate large-area, high-resolution, stretchable pressure sensor arrays for e-skin at low cost by integrating organic semiconductors, AgNW conductors, and elastomers. The devices will be fabricated using several scalable nanomanufacturing techniques including gravure printing, transfer printing, and electrohydrodynamic (EHD) printing.

The objective of this research is to develop semi-transparent organic solar modules integrated with greenhouses along with engineered plant photo-action spectra that synergistically provide food and energy sources while conserving water for a new food-energy-water paradigm.

The research objectives of this proposal are to provide a fundamental framework for the thermo-mechanical behavior of polymer semiconductor films and interfaces, and develop correlations between mechanical and electrical behavior of organic electronic devices. The education objectives of this proposal are to (1) establish a strong interdisciplinary training environment for students involved in the proposed research, (2) introduce formal course track(s) in the Mechanical Engineering Department that prepare graduate students for careers in electronics; and (3) actively participate in STEM outreach activities.

The proposed work will investigate a new and novel application of new detector technologies that can intrinsically achieve polarization sensitive detection. Such a device is beneficial for optical communications, remote sensing, quality control, and biomedical imaging in that inherent systematic errors (image registration and temporal errors) in current state-of-the-art systems can be eliminated. To our knowledge, investigating the use of our proposed method is unique; thus, several new areas of research and commercialization can be realized if prototypes and models can be researched, created, and validated.

Organic semiconductors have the potential to revolutionize macroelectronic devices including solar cells and displays. Organic solar cells, in particular, may provide renewable energy that is cost competitive with fossil fuel sources. A key aspect of this technology is the inherent flexibility and low temperature processing methods of the organic materials. These attributes allow for low cost roll-to-roll production onto lightweight plastic substrates with potential for simpler installation in traditional implementation settings as well as employment in unique applications afforded by their thin film flexible characteristics. While flexibility is critical to the success of organic solar cells, there has been limited research into the mechanical properties of the active layer of these devices. The proposed research aims to investigate the mechanical properties of the active layer of organic solar cells.

The key performance metrics of solar cells for space applications differ significantly from metrics for terrestrial applications. A premium is placed on specific power (power per unit mass), launch stowed volume (power per unit volume), and environmental tolerance. For both small and large satellite applications, large, stiff, and heavy solar panels are extremely limiting. Organic solar cells have several key benefits including flexibility and extremely high power density that make them very attractive as a power source for future space applications. These benefits have lead to recent interest in studying organic solar cells for space applications, however many questions remain. The proposed research aims to understand the physical stability of organic solar cells in a space environment with a focus on the thermal stability and impact tolerance. The funding period covered by the grant will establish important metrics for the performance of organic solar cells in space. From the experimental results of this study along with ongoing research on the effect of radiation on polymer solar cells, a organic solar cell module optimization and feasibility analysis will be performed.

Organic field effect transistors (OFETs) are rapidly becoming a competitive transistor technology for use in a range of electronic devices particularly where low-cost and large areas are important. These devices are typically based on small molecule or polymer semiconductors and can be fabricated on plastic substrates enabling flexible electronics. While devices that employ small molecules have the best performance they are often more difficult to process than their polymer counterparts. Blend films of small molecules and polymers have recently been shown to have synergistic properties that allow for low-cost solution processing while enhancing the transistor performance. Transistors based on blend films work so well, in part due to the vertical segregation of the two materials, allowing for the high performance small molecule semiconductor to form large crystalline domains directly adjacent to the gate dielectric where the charge transport occurs. These large crystalline domains are critical for efficient charge transport. The goal of the proposed research effort is to develop blend film OFET architectures that are high performing, flexible, and physically robust. A focus will be placed on studying the mechanical properties of the blend films by using a buckling based metrology method. By placing the thin blend film on an elastic host material and compressing the composite structure, a characteristic buckling pattern develops from which the mechanical properties of the thin film can be measured. The mechanical properties that are measured will guide the development of high flexible blend films. Along with the buckling metrology, flexible OFETs will be fabricated using a plastic substrate such as PET and the performance of the device will be tested in detail while under varying levels of flexure. Blend film compositions will be varied and processing methods will be developed to optimize both the mechanical and electrical properties of this very promising device concept.