Nanocellulose In Dye Solar Cells 8.3.2016 Katariina Solin Supevisors: Kati Miettunen, Maryam Borghei

Motivation The spatial variation of electrolyte components in conventional DSC The sealing of the cell with liquid electrolyte No leakage Solar Power Breakthrough: New Inexpensive, Environmentally Friendly Solar Cell | PlanetSave

Dye-sensitized Solar Cells (DSC) Thin film solar cells Photoelectrochemical system Semiconductor between photo-sensitized anode and electrolyte Porous layer of TiO 2 nanoparticles + molecular dye (anode) Platinum based catalyst (cathode) When placed in the sun, photons of the sunlight can excite electrons on the p-type side of the semiconductor, a process known as photoexcitation. In silicon, sunlight can provide enough energy to push an electron out of the lower-energy valence band into the higher-energy conduction band. As the name implies, electrons in the conduction band are free to move about the silicon. When a load is placed across the cell as a whole, these electrons will flow out of the p-type side into the n-type side, lose energy while moving through the external circuit, and then flow back into the p-type material where they can once again re-combine with the valence-band hole they left behind. In this way, sunlight creates an electric current.(http://www.specmat.com/Overview%20of%20Solar%20Cells.htm)

Dye-sensitized Solar Cells (DSC) Sunlight creates an electric current: Sunlight passes through the transparent electrode into the dye layer → excite electrons that flow into the TiO 2 → diffusion Flowing through the external circuit → electrons are re-introduced into the cell on a metal electrode Electron flow into the electrolyte The electrolyte transports the electrons back to the dye molecules When placed in the sun, photons of the sunlight can excite electrons on the p-type side of the semiconductor, a process known as photoexcitation. In silicon, sunlight can provide enough energy to push an electron out of the lower-energy valence band into the higher-energy conduction band. As the name implies, electrons in the conduction band are free to move about the silicon. When a load is placed across the cell as a whole, these electrons will flow out of the p-type side into the n-type side, lose energy while moving through the external circuit, and then flow back into the p-type material where they can once again re-combine with the valence-band hole they left behind. In this way, sunlight creates an electric current.(http://www.specmat.com/Overview%20of%20Solar%20Cells.htm) National Institute for Materials Science (NIMS) | http://www.nims.go.jp/group/g_dye-sensitizes-solar-cells/index_e.html

Nanocellulose Bacterial cellulose films and electrospun fibers Derived from abundant and renewable resources, non-toxic Thin films Highly porous Absorbing sponge

Solar Cells with Nanocellulose Method to deposite electrolyte in DSC Nanocellulose absorbs the electrolyte No electrolyte pumping needed → no uneven distribution of electrolyte components Molecular filtering effect No filling holes → simplifies the sealing of the cell Miettunen, K. et. al. Nanocellulose aerogel membranes for optimal electrolyte filling in dye solar cells. Nano Energy. 2014. Vol. 8. pp. 95-102.

Solar Cells with Nanocellulose Bacterial cellulose films and electrospun nanocellulose Cell assembly Miettunen, K. et. al. Nanocellulose aerogel membranes for optimal electrolyte filling in dye solar cells. Nano Energy. 2014. Vol. 8. pp. 95-102.

References Miettunen, K.; Vapaavuori, J.; Tiihonen, A.; Poskela, A.; Lahtinen, P.; Halme, J.; Lund, P. Nanocellulose aerogel membranes for optimal electrolyte filling in dye solar cells. Nano Energy. 2014. Vol. 8. pp. 95- 102. Miettunen, K.; Halme, J.; Lund, P. Spatial distribution and decrease of dye solar cell performance induced eletrolyte filling. Electrochemistry Communications. 2009. Vol. 11. pp. 25-27. Miettunen, K.; Asghar, I.; Mastroianni, S.; Halme, J.; Barnes, P.R.F.; Rikkinen, E.; O'Regan, B.C.; Lund, P. Effect of molecular filtering and electrolyte composition on the spatial variation in performance of dye solar cells. Journal of electroanalytical chemistry. 2012. Vol. 664. pp. 63-72. Miettunen, K.; Barnes, P.R.F.; Li, X.; Law, C.H.; O Regan, B.C. The effect of electrolyte filling method on the performance of dye sensitized solar cells. Journal of Electroanalytical Chemistry. 2012. Vol. 677-680. pp. 41-49. Hashmi, G.; Miettunen, K.; Peltola, T.; Halme, J.; Asghar, I.; Aitola, K.; Toivola, M.; Lund, P. Review of materials and manufacturing options for large area flexible dye solar cells. Renewable & Sustainable Energy Reviews, 2011. Vol. 15, nro 8, pp. 3717-3732. O’Regan, B.; Grätzel, M.; A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature, 1991. Vol 353, pp. 737-740