Novel, High-Efficiency, Light-weight, Flexible Solar Cells as Electrical Power Generation Source
Navy STTR 2016.A - Topic N16A-T006
NAVAIR - Monica Clements - navair.sbir@navy.mil
Opens: January 11, 2016 - Closes: February 17, 2016

N16A-T006 TITLE: Novel, High-Efficiency, Light-weight, Flexible Solar Cells as Electrical Power Generation Source

TECHNOLOGY AREA(S): Materials/Processes, Sensors, Space Platforms

ACQUISITION PROGRAM: PMA 262, Persistent Maritime Unmanned Aircraft Systems

OBJECTIVE: Develop a capability for high power conversion efficiency and stability in organic solar cells based on novel materials and an innovative device to create a reliable power generation source for naval aviation applications.

DESCRIPTION: Solar cells convert sunlight energy into usable electric power due to the photovoltaic effect. The key measure of performance of solar cells is power conversion efficiency, which is defined as the ratio of energy output from the solar cell to the input energy incident on it from the sun. Current semiconductor based solar cells (Silicon, GaAs) demonstrate high efficiencies (up to 50%). These solar cells are manufactured by complex capital and labor intensive processes, which, in combination with the scarcity of source materials availability, limits the ability to reduce cost, limits scale up, and prevents widespread applications.

Plastic cells, otherwise known as organic solar cells, use conducting polymers or inorganic materials for light absorption and charge transport to produce electric power. They allow the use of abundant, non-toxic materials that can be built on flexible substrates, and represent transformative technology. The conformal, light-weight, flexible feature of such plastic cells producing electric power reliably is attractive for naval applications, especially for unmanned aircraft systems (UAS). However, novel material discoveries in conjunction with innovative device designs, demonstrating high efficiencies are needed to integrate such solar cells into target applications.

Current UASs are designed to provide tactical intelligence, surveillance and reconnaissance (ISR) capabilities that enable mission planning and execution. The real time ISR needs force constraints on space, weight, and power (aka SWaP), and most importantly, flight endurance of the UAS. A limiting factor for successful mission performance is the lack of reliable high efficiency power generation systems with high power and energy densities. Though, lithium-ion battery technology can act as such a power source, it is limited by safety concerns as well as a limited time of use as a power source, requiring frequent recharging. There is a need for a source that generates power on a continuous basis to enable increased duration missions for the UAS.

Recent advancements where photovoltaic function in solar cells has been demonstrated using the perovskite class of materials acting as light-harvesting layers in hybrid organic-inorganic configuration has significantly improved efficiencies from 3.8% to about 20%. The advancement is achieved by fine tuning the material properties such as charge mobility, band gap, and energy levels to maximize photo voltage, light absorption, and charge carrier transport, respectively [2-5]. A notable feature is that such solar cells are reported to have exhibited steady performance over significant periods of time without degradation.

A key hurdle for the implementation of these thin film solar cell technologies is the prohibitive cost ($/Watt basis). Scalability is another concern, since conventional silicon solar cell manufacturing processes are harder to scale up. There is a need for the thin film solar cells to be manufactured by a low cost process that is not only scalable, but also leverages well-developed industry manufacturing methods [6-10]. An example of efficient, low cost manufacturing is the roll to roll (R2R) processes on large area flexible substrates, used in the electronic industry. To reduce manufacturing cost up to 50%, devices need to be built using low temperature process steps using large area coating or printing methods.

The objective is to develop high-efficiency, non-silicon based plastic cells with novel materials, novel device designs, innovative architectures, and to demonstrate the cells as reliable sources of power generation as applicable to naval aircraft [11-13]. Novel tandem cell designs with heterojunction device structures, which facilitate the absorption of significant portion of the solar spectrum to boost the overall efficiency, can be part of the invention. In addition, manufacturing processes that hold promise in terms of scalability, reduced process cost, and complexity, while retaining structural integrity and providing stable performance over an extended period of time are required.

The generated electric power should be stored using energy storage technologies (EST), such as batteries and capacitors with high energy density storage capability to improve the operational effectiveness when solar irradiation is not available. Offerors must include EST as part of the prototype demonstration. Novel EST designs where devices are an integral part of the air vehicle structure can be a part of the innovation.

PHASE I: Develop concept for solar cell devices incorporating novel materials and advanced designs to achieve high-efficiencies (= 20%) at standard air mass (AM) 1.5 conditions. Demonstrate the feasibility and stability of the conceptual solar cells through analytical methods and or limited testing. Compare results with a baseline control (= 500 hrs).

PHASE II: Fully develop the concept conceived during Phase I into prototypes of solar panels with cells and modules and perform detailed characterizations such as carrier lifetime, electroluminescence, and current-voltage measurements as a function of temperature to optimize spectral response and extend stability to enable the solar cells last for several years. Apply modeling and simulation tools as necessary. Demonstrate innovation to adapt scalable, robust manufacturing processes to produce flexible solar cells. Independent verification of the efficiency is strongly recommended.

PHASE III DUAL USE APPLICATIONS: Perform verification and validation. Demonstrate the functionality of conformal, light-weight solar panels that meets the electrical power needs of aircraft in a safe and effective manner in an operational environment. Transition the technology to appropriate Navy platforms (ex. UAS systems), obtain flight certification, and commercialize the technology. The high power conversion efficiency combining with stability of the solar cells act as a reliable power source for naval aircraft. The flexible nature allows conformal wrap and integration into an air vehicle without any significant weight penalties. Improvements made under this topic will tremendously benefit the commercial aviation, consumer, and automobile markets including the recent FAA approval for civilian use of drones.

REFERENCES:

1. Green, M.A., Solar Cells, Operating Principles, Technology and System Applications, Prentice-Hall Publishers, 1982, NJ, USA

2. Gratzel, M., Photoelectrochemical Cells, Nature, 414, 338-344, 2001

3. Kojima, A., Teshima, K., Shirai, Y. &Miyasaka, T., (2009). Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells, J. Am. Chem. Soc., 131, 6050-6051

4. Malinkiewwicz, O., Yella, A., Lee, Y.H., Espallargas, G.M., Gratzel, M., Nazeeruddin, M. K. & Bolink, H., (2014). Perovskite Solar Cells Employing Organic Charge-Transport Layers, Nature Photonics, 8, 128-132

5. Zhou, H., Chen, Q., Li, G., Luo, S., Song, T., Duan, H., Hong, Z., You, J., Liu, Y. & Yang, Y., (2014). Interface Engineering of Highly Efficient Perovskite Solar Cells, Science, 345, 542-546

6. Snaith, H.J. (2013). Perovskites: the emergence of a new era for low-cost, high efficiency solar cells, J. Phys. Chem. Lett. 4, 3623-3630

7. Sun, S., Salim, T., Mathews, N., Duchamp, M., Boothroyd, C., Xing, G., Sum, T.C. & Lam, Y.M., (2014). The Origin of High Efficiency in Low-temperature Solution-processable Bilayer Organometal Halide Hybrid Solar Cells, Energy Environ. Sci. 7, 399- 407, http://dx.doi.org/10.1030/C3EE43161D

8. Andersen, T.R., Dam, H.F., Hosel M., Helgesen, M., Carle, J.E., Larsen-Olsen, T.T., Gevorgyna, S.A., Andreasen, J.W., Adams, J., Li, N., Machui, F., Spyropoulos, G.D., Ameri, T., Lemaitre, N., Legros, M., Scheel, A., Gaise, D., Kreul, K., Berny, S., Lozman, O.R., Nordman, S., Valimaki, M., Vilkman, M., Sondergarrd, R.R., Jorgensen, M., Brabec C.J., & Krebs, F.C., (2014). Scalable, ambient atmosphere roll-to-roll manufacture of encapsulated large area, flexible organic tandem solar cell modules, Energy Environ. Sci. 7, 2925-2933 DOI: 10.1039/C4EE01223B and references therein

9. Roladan-Carmona, C., Malinkiewics, O., Soriano, A., Minguez_Espallargas, G., Reinecke, G.P., Kroyer, T., Dar M.I., Nazeeruddin, M.K. & Bolink, H.J., (2014). Flexible High Efficiency Perovskite Solar Cells, Energy Environ., Sci. 7, 994-997 DOI: 10.1039/c3ee43619e

10. Guo, X., Zhou, N., Lou, S.J., Hennek, J.W., Smith, J., Ortiz1, R.P., Lopez Navarrete, J.T., Li, S., Chen, L.X., Chang, R.P., Facchetti, A. & Marks, T.J., (2013). High Performance Polymer Solar Cells Achieving Exceptional Fill Factors, Nature Photonics, 7, 825-833

11. MIL-STD-810G Department of Defense Test Method Standard: Environmental Engineering Considerations Laboratory Tests (31 Oct 2008). Retrieved from http://everyspec.com/MIL-STD/MIl-STD-0800-0899/MIl-STD-810G_12306/

12. MIL-PRF-461F Department of Defense Interface Standard: Requirements For the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment (10 Dec 2007). Retrieved from http:// everyspec.com/MIL-STD/Mil-STD-0300-0499/MIl-STx-461F_19035/

13. MIL-STD-704F, DEPARTMENT OF DEFENSE INTERFACE STANDARD: AIRCRAFT ELECTRIC POWER CHARACTERISTICS (12 MAR 2004). Retrieved from http://everyspec.com/MIL-STD/MIL-STD-0700-0799/MIL-STD-704F_1083/

KEYWORDS: Solar Cells; Plastic Cells; Material Innovation; High-Efficiency and Conformal; Reliable Power Source; Unmanned Aircraft Systems

TPOC-1: 301-342-0365

TPOC-2: 812-854-4082

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