Broad-Spectrum PV Devices Based on Charged Quantum Dots

ABSTRACT: This project addresses the need for high-efficiency broad-spectrum PV cells. The proposed original PV design is based on quantum dots with built-in charge (Q-BIC), where the dot charging is realized by selective doping of dot medium. The preliminary data demonstrate that the charged dots placed in a single p-n-junction strongly enhance harvesting and conversion of sub-bandgap photons and increase the light trapping and absorption of the above-bandgap photons. The charged dots provide effective tool for engineering of 3D nanoscale potential, management of photoelectron processes, and suppression of recombination losses. For the broad-spectrum conversion the Q-BIC devices employ broad-range distribution of dot sizes. Together with selective doping the charged dots allow for optimization of microscale potential profile in the entire PV device. Plasmonic effects in charged dot layers have a potential to provide enhancement of long-wavelength absorption. The proposed program starts with design, growth, and optimization of Q-BIC photovoltaic nanomaterials with the reduced wetting layer and vertically correlated quantum dots in blocks of dot layers. The program includes complex material characterization, design of PV devices, device processing, and electro-optic testing. The Q-BIC technology is a promising basis for cells capable of converting of 35% and above into electric power. BENEFIT: This project is aimed on the development of high-efficiency, broadband, radiation-resistant, light-weight, and relatively low-cost PV devices which can be used by residential users, industry, and military. A specific subset of the PV market where such cells have a large and immediate impact is concentrating photovoltaics (CPV). Whilst only 90 MW are estimated to be installed in 2012, installations are predicted to increase rapidly over the next four years. CPV units that are more efficient will require less material, less real estate, and therefore less cost. The Q-BIC solar cells have a potential to successfully compete with multi-junction solar cells on CPV market and can be used for various AFOSR missions. The Q-BIC PV devices are tolerant to the temperature variations and can operate under all-weather conditions providing strong harvesting and conversion of IR radiation. The benefits of development of Q-BIC PV devices are in: (a) product scalability; (b) manufacturing architecture consistent with current cell / semiconductor processing equipment with minimal modification to reduce new capital costs; (c) a combination of cost and performance that is materially better (15-20% LCOE reduction) than the competing solutions; and (d) expansion of the Q-BIC technology to a wide range of solar cell architectures.