Organic and Perovskite-based Photovoltaics on Flexible substrates: Roll-to-roll Fabrication and Encapsulation
Hasitha Weerasinghe, Doojin Vak, Dechan Angmo, Mei Gao, Andrew Scully
Commonwealth Scientific and Industrial Research Organization – CSIRO, Manufacturing, Clayton, Victoria 3168, Australia.
Email: Hasitha.Weerasinghe@csiro.au,
Website: https://www.csiro.au/en/Research/EF/Areas/Solar/Photovoltaics
Perovskite-based and Organic-based solar cells (PeSCs and OPVs) fabricated on plastic substrates are attracting worldwide attention due to advantages such as flexibility, large-scale printability, lightweight, solution processability, and potential utility for new products. These properties allow PeSCs and OPVs to be manufactured by cost-effective industrial roll-to-roll processes on flexible substrates and makes the material as a good alternative of conjugated organic materials which have been widely used in printed solar films (PSFs). In this presentation, CSIRO’s activity on the roll-to-roll production of PSFs as well as the typical roll-to-roll printing processes will be introduced and requirements of materials/processes to be used in roll-to-roll production will be addressed. CSIRO has been working on organic based PSFs for a decade and now tackling printability (roll-to-roll compatibility) of perovskites as well as other components of PeSCs. Roll-to-roll processed/compatible electrode, charge transport layers and perovskite layers [1-2] will be presented and challenges toward the manufacturing of fully printed PeSCs will be discussed. Recently, we have demonstrated roll-to-roll processed perovskite-based devices using a modified sequential deposition method. This printing-friendly sequential deposition has been used in air with slot die coating, an industrial up-scaling technique, to produce a perovskite solar cell on flexible substrates up to 11.0% PCE.
However, poor long‐term stability of PeScs and OPVs limits the future commercial application. Exposure of these devices to atmospheric oxygen and water vapour is known to cause rapid device degradation. Encapsulation using materials having ultra-low permeability to these atmospheric constituents is required to achieve sufficient operational lifetimes for commercial applications. We have found that pre-entrained moisture in the encapsulation materials, and post-encapsulation ingress of moisture/oxygen through adhesive layers and around electrical contacts are significant lifetime-limiting factors. Encapsulation architectures were developed using a variety of flexible barrier films and adhesives to address these issues, and the lifetime of encapsulated large-area (active area ~50 cm2) fully-printed OPV having efficiency >3% modules were assessed under various storage conditions. New encapsulation architectures were found to significantly enhance the durability of printed OPV modules, with results showing modules exhibiting a shelf-life of more than 5 years under ambient conditions and durability of more than 4 years under exposure to outdoor conditions [3-4]. The effect of encapsulation on improving the operational lifetime of flexible perovskite-based solar cells prepared on polymer substrates having efficiency exceeding 13% was also studied. The lifetime of the encapsulated flexible PSC devices was extended significantly compared with that of the non-encapsulated devices. Permeation testing revealed that the post-encapsulation ingress of moisture through the adhesive layers and around electrical contacts constitutes a significant lifetime-limiting factor [5].
References
[1] K. K. Sears, M. Fievez, M. Gao, H. C. Weerasinghe, C. D. Easton, and D. Vak, Solar RRL (2017) 1, 1700059.
[2] Y.-J. Heo, J.-E. Kim, H. Weerasinghe, D. Angmo, T. Qin, K. Sears, K. Hwang, Y.-S. Jung, J. Subbiah, D.J. Jones, M. Gao, D.-Y. Kim, D. Vak, Nano Energy, 41 (2017) 443-451
[3] H.C. Weerasinghe, N. Rolston, D. Vak, A.D. Scully, R.H. Dauskardt, Solar Energy Materials and Solar Cells, 152 (2016) 133-140
[4] D. Vak, H. Weerasinghe, J. Ramamurthy, J. Subbiah, M. Brown, D.J. Jones, Solar Energy Materials and Solar Cells, 149 (2016) 154-161
[5] H.C. Weerasinghe, Y. Dkhissi, A.D. Scully, R.A. Caruso, Y.-B. Cheng, Nano Energy, 18 (2015) 118-125.
Fig 1. (a) Fully-printed 10cm × 10cm size OPV module, (b) Schematic diagram of printing-friendly sequential slot die coating of a perovskite layer
Fig 2. (a) Roll-to-roll slot die coating of Perovskite and (b) roll-to-roll coating of organic photo-active layer. (C)Fully-printed 30cm-wide organic PSFs produced at CSIRO.