Polymer-Nanomaterial Composite Solar Cells

M. Faisal Halim

Dorsinville Group

Friday, 5th November, 2010

Aim

• To make high efficiency solar cells that are:– Cheap– Mechanically Flexible– Have High Efficiency– Are Solution Processible

• Can take Advantage of Molecular Self Assembly• Processes are highly scalable

– Provide for Ease of Fabrication– Producible by Low Toxicity of Processing Methods

Physical Processes to Effect [1]

• Photon Absorption

• EHP Dissociation

• Electron andHole Conduction

Source: Solar Energy Materials and Solar CellsVolume 87, Issues 1-4, May 2005, Pages 733-746

Composite Components

• Quantum Dots(CdSe)

• Carbon Nanotubes(Single Walled),S-SWCNT,M-SWCNT

• Polymer(Semiconducting, p-type)

Absorption Spectrum of CdSe QDs (aq)

Absorption Spectrum of SWCNTs (aq)

Absorption Spectrum of 6 Layer Film of SWCNT in P3OT

What We Want To Do

• Immobilize/Bind/Self-Assemble Quantum Dots onto SWCNTs. [2-10]

• Encapsulate QD covered SWCNTs with a semiconducting polymer (This will give the Active Material) [11-12]– Encapsulation is required for EHP dissociation from

polymer to M-SWCNT– Amount of M-SWCNT in composite high enough (1%

ww) to allow for percolation• Sandwich by spin coating onto PEDOT:PSS

coated ITO covered substrate and evaporating a metal (Al) electrode

QD Immobilization

• Provides PhysicalContact for electrontransfer fromQD to SWCNT– Treatment of QDs

• ATP [2,4-10]

– Treatment ofSWCNTs

• Depends on typeof attachment [2-10]

QD-SWCNT Encapsulation in Polymer

• Dissociates EHP(preventsrecombination)[11-12] – Electron delocalized

and transported toQD or SWCNT

– Hole localized onpolymer chain

What we need to do

• Ligand exchange of decylamine with a conjugated system

• SWCNT Surface Treatments for Non-covalent binding (self assembly, based on available number of quantum dots)

References1. Solar Energy Materials and Solar Cells Volume 87, Issues 1-4, May 2005, Pages 733-7462. Light-Induced Charge Transfer in Pyrene/CdSe-SWNT Hybrids, Volume 20, Issue 5, pages

939–946, March, 20083. Tailored Single-Walled Carbon Nanotube−CdS Nanoparticle Hybrids for Tunable

Optoelectronic Devices, ACS Nano, 2010, 4 (1), pp 506–5124. Synthesis of high quality zinc-blende CdSe nanocrystals and their application in hybrid solar

cells, Lili Han et al 2006 Nanotechnology 17 47365. CdSe quantum dot-single wall carbon nanotube complexes for polymeric solar cells, Solar

Energy Materials and Solar Cells, Volume 87, Issues 1-4, May 2005, Pages 733-7466. Noncovalent attachment of CdSe quantum dots to single wall carbon nanotubes, Materials

Letters, Volume 60, Issues 29-30, December 2006, Pages 3502-35067. Breakthroughs in the Development of Semiconductor-Sensitized Solar Cells, J. Phys. Chem.

Lett., 2010, 1 (20), pp 3046–30528. Materials, Nanomorphology, and Interfacial Charge Transfer Reactions in Quantum

Dot/Polymer Solar Cell Devices, J. Phys. Chem. Lett., 2010, 1 (20), pp 3039–30459. Ligand-Tuned Shape Control, Oriented Assembly, and Electrochemical Characterization of

Colloidal ZnTe Nanocrystals, Chem. Mater., 2010, 22 (16), pp 4632–464110. Controlling Charge Separation and Recombination Rates in CdSe/ZnS Type I Core−Shell

Quantum Dots by Shell Thicknesses, J. Am. Chem. Soc., 2010, 132 (42), pp 15038–1504511. Why is exciton dissociation so efficient at the interface between a conjugated polymer and an

electron acceptor? APPLIED PHYSICS LETTERS VOLUME 82, NUMBER 2512. Exciton Dissociation in Organic Light Emitting Diodes at the Donor-Acceptor Interface, PRL

98, 176403 (2007)

Results of Discussions from the Meeting

• SWCNTs: we will acid treat them (H2SO4, or something else – I will have to look for what we may need to buy) to create defect sites where the QDs can settle and immobilize for QD-SWCNT electron conduction.

• Devices will need to be built to compare acid treated (SWCNT) vs. untreated device performance.

• Z-scan will need to be done for active materials, though it is unlikely that a difference will be noticable for acid treated vs. untreated SWCNT (with QD) devices.

• At some point pump and probe femto second dynamics of treated vs. untreated devices will have to be measured.

• AFM and TEM are unlikely to be able to distinguish between acid treated and untreated devices, though Raman might be able to tell.

• We may have to do ligand exchange of QD surfactant – need to see what surfactant to buy.