We recently started a new program at ASU to work on one of the most challenging problems in photovoltaics. How to grow thin wafers of crystalline silicon directly from the gas phase and then process them into solar cells. The program takes advantage of technology that we recently developed to produce record voltages on crystalline silicon solar cells.
The surfaces of silicon solar cells are highly active and a major loss mechanism unless they are made electrical inactive by passivation of the surface defects. Silicon nitride is commonly used to passivate the front surface of solar cells and gives them their blue color. The positive charge in the nitride lowers the electrical activity at the surface of n-type material by repelling minority carrier holes. Recently we demonstrated a techniue to change the charge in silicon nitride from positive to negative. By flipping the charge we will be able to use silicon nitride to passivate p-type. The whole process is done at low temperature and relies on changing a metastable defect.
The results are published in V. Sharma, C. Tracy, D. Schroder, S. Herasimenka, W. Dauksher, and S. Bowden, “Manipulation of K center charge states in silicon nitride films to achieve excellent surface passivation for silicon solar cells,” Applied Physics Letters, vol. 104, no. 5, p. 053503, Feb. 2014. http://dx.doi.org/10.1063/1.4863829
Solar power benefits people across the world. At the solar power lab we focus on the device physics of photovoltaic devices and ways to increase the performance while lowering the cost. We also get out into the community to see how solar power can be used to directly benefi people lives. Most of our outreach takes place closer to home but in the first two weeks of 2014 one of our graduate students, Tim Reblitz, travelled to Uganda to look at how solar is used there. Most of the education was for Tim but we hope that there were also benefits to the local Ugandian community. You can read more about Tim's exploits at his blog
We have recently started cross linking pages between pveducation.org and pvlighthouse.com.au. The animations and interactive graphs at pveducation.org focus on explaining photovoltaic concepts. PV Lighthouse is a repository of more detailed simulation programs for photovoltaics. The programs are free and can be accessed as online calculators or downloadable applications. PV Lighthouse also maintains libraries of photovoltaic data, such as common spectra and the refractive index of materials. Researchers that contribute to PV Lighthouse are given a profile page and are regularly provided with statistics that quantify the global interest in their programs. The ultimate goal of PV Lighthouse is to integrate all programs and data into a single grand unified model of photovoltaics.
This course will focus on the science and technology involved in the manufacturing of solar cells and will provide students with an introduction to important manufacturing concepts such as device design, yields, throughput, process optimisation, reliability, in-line quality control and fault diagnosis. In this class, students will learn about: (i) the fabrication processes of the commercially-dominant screen-printed solar cells; (ii) the impact of various processing and device parameters on performance, yields and product reliability; and (iii) in-line, endof-line and failure-analysis quality control techniques, and (iv) trends in commercial cell technology and the corresponding manufacturing processes. Students will be given the opportunity to take control of a "virtual solar cell production line" to adjust the equipment controls and processing parameters to try and optimise performance and maximise virtual production yields. In-line quality control procedures are available to the student to aid in this optimisation and will prove to be particularly useful in identifying and rectifying weaknesses or problems associated with the production.
The use of photovoltaics (PV) has increased dramatically over the last years, driven by cost reductions in the PV systems. The goal of the course is to be able to calculate, design and understand the components of PV systems; design and optimize a PV system for a range of PV applications; to be able to calculate and analyze the initial and levelized cost of PV electricity; understand and analyze the reliability of the PV systems; and to understand how non-technical barriers and incentives affect PV Systems.
The Solar Power Labs is featured on STEM journals on Cox Ch. 7. It is originally broadcast on Nov 20 at 8 pm and is archived on the web at: http://www.cox7.com/alternative-energy Our section starts at time 12:50.
Surface recombination is a critical parameter that determines the perfromance of thin silicon solar cells. We have developed a passivation process with very low recomination giving very high minority lifetimes in crystalline silicon exceeding 60 ms.
The paper is publlished online at Applied Physics Letters: ]S. Y. Herasimenka, C. J. Tracy, V. Sharma, N. Vulic, W. J. Dauksher, and S. G. Bowden, “Surface passivation of n-type c-Si wafers by a-Si/SiO2/SiNx stack with <1 cm/s effective surface recombination velocity,” Applied Physics Letters, vol. 103, no. 18, p. 183903, Oct. 2013..
At the solar power labs we have opportunities for students starting in Spring 2014. There are Engineering Dean's felllowships available for US Citizens with good grades. For more details on the Dean's fellowships please see the link: