Ultrahigh Efficiency Quantum Dot Multi-photon Photovoltaics using Nipi Lateral Architecture

Higher efficiency solar cells are needed to reduce solar array mass, volume, and cost for Air Force space missions. Intermediate-band quantum-dot (QD) solar cells can yield dramatically higher efficiencies than current multi-junction (MJ) technologies. However, several issues must be addressed to demonstrate manufacturable, high efficiency devices. CFDRC aims to develop: 1) High-efficiency, lighter, radiation-tolerant QD nipi (n-i-p-i doped) solar cells, and 2) new, validated computational tools for real shape QD nanostructures. We expect that QD solar cells can achieve efficiencies of 52%, due to optimized absorption across solar spectrum (“multicolor” cell) and quantum confinement of photogenerated carriers and phonons in QDs. Customized modeling tools will be used for QD optimization, including: (i) geometrical ordering and variable QD size, (ii) increased transport and separation of photogenerated carriers; (iii) improved electrical conductivity and enhanced collection efficiency. Phase I work will include modeling and experimental design of QD nanostructured nipi devices capable of fully absorbing the solar spectrum, and efficiently collecting generated carriers utilizing a multi-photon conversion process. Theoretical efficiency of device will be determined. In Phase II, physical mechanisms limiting performance will be identified, leading to optimized device design. The nipi nanostructure cells will be fabricated and prototypes will be delivered. BENEFIT: Air Force space missions require improvements in solar cell efficiency and radiation hardness. Significantly increased photovoltaic conversion efficiency will enable high power platforms supporting higher bandwidth communications and high power radars for space based applications. In addition, higher power per area could enable body mounted solar cells for some spacecraft, greatly increasing space mobility and allowing spacecraft to be built and launched faster. The potential low costs and high manufacturability of nanostructured solar cells will further remove the solar array as a cost driver allowing for plug-and-play array solutions to be developed. The inherently radiation tolerant quantum dots will lead to more robust space defense systems. The new modeling and simulation tools for quantum-dot-based nanostructures will help Air Force to: a) assess technologies, devices, and materials for new efficient photovoltaic solar cells; b) better evaluate the performance and radiation response at early design stage; c) set requirements for hardening and testing; reduce the amount of testing cost and time. In addition, low costs of manufacturing could allow these new solar cells to compete for terrestrial applications such as distributed power or grid power replacement/backup. Potential commercial applications will occur through the development of high performance (high W/kg, high W/m2, and low $/W) cells that could be used for terrestrial and space applications for both the military and commercial sectors. All satellites, military and commercial, suffer from solar cell degradation due to the effects of radiation. The higher efficiency of the novel quantum-dot solar cells will increase capacity of the solar array at the beginning of life (BOL) to compensate for the degradation at the end of life (EOL), to maintain the minimal power generation requirements of the spacecraft or satellite system.