7/5 Speech， Topic： Scaling Up Thin Film PV Technology
Speaker：Dr. Yulia Galagan
Organization：TNO – Solliance Eindhoven, the Netherlands
Scaling Up Thin Film PV Technology: How the Fundamental Knowledge Helps to Solve the Multidisciplinary Issues Toward Industrial Manufacturing
Date：10:00 , 2019.7.5
Location：Room 243, College of Engineering
Yulia Galagan is a Senior Scientist and Project Manager at TNO/Solliance (the Netherlands Organisation for applied scientific research). She received her Ph.D. in chemistry in 2002 from Kyiv University. During her PhD and the first few years of her research career she worked on the development of superconducting ceramics and polymer/ceramic composites. From 2005 till 2008 Dr. Galagan was employed as a research fellow at National Taiwan University, where she started her research in the field of organic and hybrid solar cells. In 2008 she joined TNO/Holst Centre. Her research interests are focused on organic and perovskite-based electronics (PVs, LEDs, sensors), from fundamental aspects to large area processing. Dr. Galagan has an expertise in the development of emerging materials for sustainable energy conversion, optoelectronics and bio-electronics with adjustable physical properties. Currently, Yulia Galagan is a group leader responsible for scale-up technologies for roll-to-roll manufacturing of perovskite photovoltaics.
Research progress in the field of organic and hybrid perovskite solar cells has increased enormously over the past years, making these technologies very promising candidates for future PV systems. The growing interest to organic and perovskite photovoltaics is driven by their promise for low-cost energy conversion. The low-cost potential is based on the use of low-cost materials and substrates and very high production speeds that can be reached by roll-to-roll printing and coating. However, the presence of a transparent conducting electrode such as indium tin oxide (ITO) limits the reliability and significantly increases the cost of flexible devices as it is brittle and expensive and has high sheet resistance limiting the dimension of the PV cells. Therefore, at the early stage of my research in the field of thin film PVs, a significant effort was put on the development of low-cost printable and highly conductive transparent electrodes [1-3]. I have invented and demonstrated a transparent electrode with the sheet resistance of below 1 Ohm/cm2. The concept is based on the current collecting grids embedded into a substrate , which was further realized in R2R manufacturing . With this invention, I was awarded the first prize “Devices of the year” at the international contest organized at International Summit on OPV stability (ISOS-3, 2010, in Denmark).
A transition from laboratory-scale fabrication to industrial manufacturing requires scaling up the dimension of the devices. In order to maintain high power conversion efficiency (PCE) and to reduce resistive losses, the geometry and the design of the grid have to be optimized. Therefore, my next contribution to the field was in the electrical simulation of the solar cells with different designs and architectures [5-8]. To be first shown in organic solar cells [5-7], the model was further exploited in perovskite photovoltaics . The developed model had good agreement with the experimental results which indicate the large area modules are feasible without efficiency losses.
The next important step toward upscaling is the development of alternative deposition methods to spin coating, which are industrially compatible and maintain high power conversion efficiency of the manufactured devices. One of the bottlenecks towards this development is the toxicity of the solvents used in the fabrication of lab-scale devices. The effect of the solvents and perovskite precursor compositions (inks) on the morphology and properties of perovskite film; and crystallization kinetics of perovskite have been systematically investigated. I used Hansen solubility model to formulate non-toxic inks for deposition of all functional layers in organic and perovskite solar cells in R2R manufacturing. Using the fundamental concepts of surface chemistry, the physical chemistry of interfaces, a coating flow dynamic of the inks were optimized in order to provide a homogenous coating over a large area, maintaining high PCE of the devices [9-12]. Alternative drying and sintering techniques (e.g. photonic flash sintering and IR annealing) and the drying dynamics of printed layers and the amount of consumed energy were also thoroughly investigated [3, 13, 14].
Further, a high PCE of the devices depends on many factors and light management is one of them. In my research, I use optical modeling to optimize the thicknesses of all layers in the devices and thereby push the performance of the devices manufactured on the R2R process towards high efficiency. The optical simulations were used in many different devices such as OPVs with ITO  and ITO-free electrodes, steel substrates , as well in the rigid and flexible perovskite solar cells, which is very important for transparent solar cells to be used in the application of tandem solar cells.
Applying fundamental scientific knowledge into the realization of semi-industrial tasks is a very important integral part of the research which allowed me to develop large area prototype for large area organic and perovskite solar cells modules [7, 9, 10, 17]. The R2R manufactured perovskite devices produced by me are currently the state of the art in terms of technology and PCE . The above works are published in high impact journals  and books [20, 21] for further references.
1. Y. Galagan et al., Sol. Energy Mater. Sol. Cells, 95 (2011) 1339-1343.
2. Y. Galagan et al., Adv. Energy Mater., 2 (2012) 103-110.
3. Y. Galagan et al., Organ. Electron., 14 (2013), 38-46.
4. Y. Galagan et al., Nanotechnology, 24 (2013), 484014.
5. Y. Galagan et al., Sol. Energy Mater. Sol. Cells, 104 (2012) 32-38.
6. Y. Galagan et al., Adv. Energy Mater., 4 (2014), 1300498.
7. Y. Galagan et al., J. Mater. Chem. A, 3 (2015) 7255-7262.
8. Y. Galagan et al., J. Mater. Chem. A, 4 (2016) 5700-5705.
9. Y. Galagan et al., Chem. Eng. Process., 50 (2011) 454-461.
10. Y. Galagan et al., Energy Technology, 3 (2015) 834-842.
11. Y. Galagan et al., Solar RRL, 11 (2017) 1700091.
12. Y. Galagan et al., ACS Appl. Energy Mater., 1 (2018) 6056-6063.
13. Y. Galagan et al., Org. Electron., 34 (2016) 130-138.
14. Y. Galagan et al., ACS Appl. Mater. Interfaces, 8 (2016), 2325-2335.
15. Y. Galagan et al., Appl. Phys. Lett., 98 (2011) 043302.
16. Y. Galagan et al. Org. Electron., 13 (2012), 3310-3314.
17. Y. Galagan et al., Sol. Energy Mater. Sol. Cells, 181 (2018) 53-59.
18. Y. Galagan et al., Adv. Energy Mater., 8 (2012) 1801935.
19. Y. Galagan, J. Phys. Chem. Lett., 9 (2018), 4326–4335.
20. Y Galagan, Flexible substrates and barriers in “Organic Solar Cells: Fundamentals, Devices, and Upscaling” ISBN 978-9814463652, Pan Stanford Publishing, (2014).
21. Y. Galagan, Roll to Roll Manufacturing in Photovoltaic Films in “Roll-to-Roll Manufacturing: Process Elements and Recent Advances”, ISBN: 9781119162209, John Wiley & Sons, Inc., (2018).