Current OPV Research Directions

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These are promising directions in organic photovoltaic research being pursued at the CMDITR

Evolution of Solar Cell Efficiency

These are the types of efficiencies that people have been able to reach. For example, with silicon, fill factors of about 0.8 and conversion efficiency, of 24% can be reached.

The Grätzel cell, which is a hybrid cell that has both organic and inorganic components and uses a liquid electronlyge, has a conversion efficiency of about 11%. Michael Grätzel is a professor at the technical school of Lausanne in Switzerland.

With polymers, Allen Heeger has recently reported a conversion efficiency of up to 6%. Our goal at this time is to reach the 10% efficiency in organic cells. However, it does not seem to be very easy to achieve.

Characteristic	Silicon	Organic (Tang)	Organic (Forrest)	Organic (Graetzel)	Polymer	Hybrid nanorods
Open circuit voltage (Voc; V)	0.7	0.45	1.02	0.721	0.63	0.7
Short circuit current density (Jsc; mA/cm2)	43	2.3	9.7	20.53	9.5	5.7
Voc x Jsc (mW/cm2)	30.1	1.035	9.894	14.80213	5.985	3.99
Fill factor (FF)	0.8	0.65	0.59	0.704	0.68	0.4
Illumination intensity (mW/cm2)	100	75	100	100	80	96.4
Conversion efficiency (%)	24.08	0.9	5.7	10.4	5.1	1.7

New materials

Research directions include using multilayers of small molecules, building polymer blends with interpenetrated networks, nanostructured oxide polymers and hybird approaches using doped inorganics in an organic matrix.

Discotic Mesophase Materials

Another kind of thalocyanine that is solution processable form molecules that self-organize into columnar stacks. This the kind of configuration that makes molecules good light absorbers and good conductors.

An AFM visualization of sheets discotic materials that have been deposited on a single crystal substrate.

Dendritic Polymers

Dendritic polymers create a spiky surface which may be able to be combined with an suitable electron acceptor layer to form a finely organized heterojunction.

Nanoparticles

Quantum dot compounds can be can be used as part of the donor or acceptor materials.

Semiconductor nanoparticles built from cadmium selenide 2-5nm in diameter take on interesting electron properties. The particle is capped with ligands to make them processable. The size of the nanoparticle determines the luminescence. The smallest make blue color, the largest makes the red. Used in a solar cell they absorb in the same color ranges.

Tailored interfaces

New hybrid materials could be used to build a solar cell step by step. Light absorbing rods are placed on a transparent base. Then the electron transport rods, and the hole blocking layer.

Fabrication Processes

There are new strategies for producing titanyl phthalocyanine (TiOPc) and C60 heterojunctions. After deposition the material can be solvent annealed resulting in nanotexturing and tunability in the NIR.

TiOPc

See Armstrong

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