Solar cells convert sunlight to electricity and have several unique advantages. They operate without monitoring, do not emit pollution, and can be made from earth-abundant and non-toxic materials. The use of solar energy is rapidly growing, but it still accounts for only a small fraction of electricity production. To increase their share of the energy market, the cost of making and operating solar cells must be decreased and their efficiency must increase. Carrier-selective passivating contacts hold the promise of doing just that. Such contacts increase cell efficiency by reducing electrical losses at the interface between the layer of a solar cell that absorbs light and the metal contacts that extract electrical current. This project will use a unique way to improve the fundamental understanding and control of loss mechanisms in solar cells with such contacts. Laser processing provides a way to electrically activate carrier-selective passivating contacts by selectively depositing laser energy into a selected layer with fine control at high speed. This process has the potential to increase the power conversion efficiency of solar cells while maintaining low temperature and high throughput, thereby decreasing the cost per kilowatt-hour of energy produced. The generated knowledge will improve various types of solar power generating as well as other electronic and photonic devices. The proposal brings together an experienced multidisciplinary team with expertise in solar cell fabrication, laser processing, and atomic-scale characterization. The PIs will engage in extensive outreach to local high schools, museums, and libraries. The economic impact will be amplified through work with solar cell manufacturing companies. This project will help society meet its future energy needs using fewer resources at a reduced cost while preventing pollution and climate change.
This project encompasses carrier-selective passivating contact development, photovoltaic device fabrication, laser processing, and imaging at the atomic level using transmission electron microscopy. Carrier-selective passivating contacted (CSPC) devices are a promising next generation technology for photovoltaic devices because they eliminate the two primary loss mechanisms: the direct metal contact to silicon and dopant diffusion into the bulk. A fundamental understanding of the interface quality, dopant type, dopant activation (and potential diffusion), tunneling mechanism, and the effect of the passivation layer is still lacking. Through a combination of device modeling, fabrication and laser processing experiments, and transmission electron microscopy studies, the quantitative degree of CSPC band bending and band gaps; effect of thermal crystallization on optical absorption, implied open-circuit voltage and defect content; and independent control of dopant activation, crystallization, grain growth, and dopant diffusion will be investigated to provide the photovoltaic industry a better understanding of CSPC for is manufacturing adoption. The novelty of the aim of this study lies in the use of pulsed laser processing of CSPC to provide a non-contact way of annealing the device with surface heating only. This work will provide a fundamental understanding of the interface properties at the atomic and nanoscale level and relate these studies to the optical and electronic properties as well as to device performance of a full-area state-of-the-art CSPC device. This project will have a broad impact by training an interdisciplinary, interuniversity, and diverse team of graduate and undergraduate students across two universities.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.