EAGER: Finite-Absorption-Bandwidth Materials for Cost-Effective Multijunction Photovoltaics

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Abstract: Nontechnical: Commercial solar cells that absorb visible light are reaching their theoretical and practical efficiency limits. An ideal strategy for improving their performance would be a new material that could simply be "stuck on top" of a current high-performing commercial cell, allowing it to harvest the invisible infrared radiation emitted by the sun. This project seeks to build a new class of flexible materials that only absorb in the infrared while transmitting visible light by using semiconductor particles with optical properties that depend on their nano- and micro-scale structures. Specifically, the goal is to make photonic crystals (structures in which certain frequency ranges of light cannot propagate) in strongly absorbing colloidal quantum dot films, to be used in color-tuned and transparent solar cells. The project has the potential to address broad societal goals in the development of more efficient renewable energy technologies, as alternatives to polluting and unsustainable fossil fuels, by developing lightweight, inexpensive, and flexible solar energy harvesting materials. Additionally, these materials could be ideal platforms for transparent and building-integrated solar cells. The project seeks to address fundamental questions on the role of different length scales in nanostructured materials, and how the interplay between them determines optical and electronic materials properties. Research activities will be integrated with a comprehensive education and outreach plan designed to introduce elementary school students, undergraduates, and graduate students to the fields of nanotechnology and sustainable engineering. Technical: The objective of this study is to build new inorganic nanomaterials with finite absorption bandwidths that will be used to improve the efficiency of transparent and multi-junction solar cells. The project will take an innovative approach for making flexible nanoparticle films with spectrally-tailored absorption and transmission spectra based on novel realizations of photonic bandgaps in strongly absorbing colloidal-quantum-dot-based thin-film materials. Methods to be employed include computational simulations, chemical syntheses, solution-processed device fabrication, and electrical and optical device characterization. If successful, the research work will result in a new method for improving the efficiency of current solar cell technology by introducing a new class of active optoelectronic materials that absorb only in the infrared. These flexible photovoltaic materials could increase the efficiency of current commercial solar cell technology in a cost-effective way: the top infrared cells will transmit visible light to the bottom standard visible cells, achieving current-matching in a multi-junction structure without re-engineering current high-performing solar cell technology. This project also aims to answer open questions involving the interactions between nano-physical phenomena, how to achieve self-assembly and optical engineering on multiple length scales, and how artificial photonic band structures can be maintained in strongly absorbing media. The novel materials developed in this project have the potential to be used in a number of new technologies, including multi-junction solar cells, transparent photovoltaics, and other photonic and optoelectronic devices.