Getting Power from Plastic – Solar Power Generation Using Blends of Organic Polymers and Nanostructures By Dave Black and Shashi Paul

Solar Power World energy demand increasing Photovoltaics currently <1% Two types –Conventional Semiconductor (CSC) –Excitonic Semiconductor (XSC)

Types of Solar Cell First Generation (CSC) Second Generation (CSC) Third Generation (CSC) Organic (XSC) Hybrid (XSC )

CSC Device Structure Encapsulation P-N junction Bottom Contact Top Contact Typical 1 st and 2 nd generation CSC solar cell structure

CSC Device Structure 3 rd generation CSC multijunction Anti Reflection coating Top Cell (GaInP) Bottom Contact Top Contact Middle Cell (GaAs) Tunnel Junction Bottom Cell (Ge) Substrate (Ge)

XSC Device Structure Transparent Substrate ITO transparent electrode PEDOT:PSS Active layer Exciton blocking layer Al/Ag electrode Typical organic heterojunction solar cell structure.

Why Organic? Potentially Cheap –Materials expensive now –Price decreases as production increases Quick to produce –Simple processes Sputtering Spin coating Thermal Evaporation Printing Flexibility –Plastic substrates –Clothing –Fabric (already used by US Army) The Voltaic Generator, by New York- based Voltaic Systems, is the first solar bag powerful enough to charge a laptop. Photograph: PR

7 Stages of Excitonic Charge Generation Photon incoupling Photon absorption Exciton formation Exciton Migration Exciton Dissociation Charge Transport Charge collection e-e- h+h+ Exciton Nano- particle e-e- h+h+

What is EMTERC Doing? Next generation hybrid PV –Novel blends of polymers and nanostructures –Increased efficiency –Increased absorption –Low cost?

Permittivity Increased Permittivity –Tune Debye Length –Control exciton type –Increase diffusion length Barium Titanate –High permittivity –Ferroelectric –Tetragonal structure

Debye Length Debye length defined as: The scale over which mobile charge carriers screen out electric fields As L D increases so does charge separation.

Increasing Permittivity Increase in relative permittivity with increasing concentration of barium titanate with phosphonic acid ligand.

Increasing Photoconductivity Increase in photo-conductivity in light and dark conditions for polymers with and without novel material.

The EMTERC Hybrid Uses blend of polymer and NP Has diode like behaviour Difference between light and dark states Work in progress

Future Work in EMTERC Incorporating Nanostructures: –Improve the number of incident photons captured by the solar cell –Improve the number and type of excitons produced from incident photons –Increase the exciton diffusion length –Increase the number and quality of interfacial boundaries Transparent electrode Aluminium electrode Nanowires Active polymer matrix

Any Questions?