Collaborators R. Norwood, J. Thomas, M. Eralp, S. Tay, G. Li, College of Optical Sciences, S. Marder, Georgia Tech. M. Yamamoto, NDT Corp. N. Peyghambarian University of Arizona College of Optical Sciences Nanoengineered Organic Photonic Materials and Devices

Outline  Organic Nanostructures and Functional Composites  Electronic Transport in Organics and Comparison with Inorganics like Semiconductors  An Example: Photorefractive Polymers, Multi-color Sensitive Polymers  Optimization of Performance by electron transfer Advantages of Organics: Large size Several ft 2, light weight, ease of processing, inexpensive

Organic Nanostructures SemiconductorsOrganics Quantum dotsMolecules or polymers R (nm) L PbS

Example: Thin layer of PS/PMMA film Courtesy: Nanosurf AG 7-DCST C 60 MoleculesPATPD7-DCSTECZC 60 Size (nm) PATPD M W =18,000 Number of units = 28 Organic Nanostructures

SemiconductorsOrganics Band StructureHOMO and LUMO AjAj AiAi Positional Energetical - - Hopping TransportBand Transport

Assembling Organic Nanostructures into Functional Composites for Applications OLEDs Thin layers of pure material evaporated or spin-coated EO Polymer Modulators Organic Photorefractives Application Assembly Nanostructures Mixing of a structural polymer with a single functional component Mixing of several multifunctional components PPV PATPD 7-DCST Alq3 AJ309 C 60

Photorefractivity in Polymer Composites Convert an intensity distribution into a refractive index distribution  Sensitizer  Transport  Chromophore  Plasticizer

SLM Beam- Splitter Reference Beam PR Polymer Film Object Beam Holographic Recording Reading Beam Observer or CCD Rewritable Holographic Recording and Display

Photorefractive Polymer Applications Updatable 3D Display

Energetic and Electron Transport

Photorefractive Polymers (Guest Host Composites) Chromophore Transport Photogeneration of carriers Polymer matrix Sensitizer Electro-optic activity Reducing Tg Plasticizer + Low-cost, ease of fabrication and control over properties - Bias Field

Transport matrix Chromophores Vacuum level PATPD (eV) 5.6 DBDC 7-DCST C Plasticizer PATPD/ECZ/7DCST/DBDC/C 60 – 633 nm PATPD/ECZ/7DCST/TNFDM – 845 nm PATPD/ECZ/7DCST/DBM – 975 and 1550 nm Sensitizer Molecular Energetics TNFDM

Linear Absorption PATPD:7-DCST:APDC:ECZ:DBM / 49:25:25:10:1 PATPD:7-DCST:ECZ:C60 (54.5:25:20:0.5 wt.%) nm 1550nm 775nm Optical Density Wavelength(nm) PR polymer sensitive for green to red PR polymer sensitive to IR

Grating Writing and Reading Thick-grating: Typical values:  = 633 nm d = 20  m  ~ 3  m  Q= 2.3

Performance of PR Polymers M. Eralp, et al, Opt. Lett, Accepted Diffraction efficiencyResponse time Voltage (kV) Int. Diffraction Efficiency jt163 jt223

Two Beam Coupling Gain PATPD:DBDC:ECZ:C60 (49.5:30:20:0.5 wt.%)

SensitizerHole-transportChromophore h Optimization of Photorefractive Polymers

Ip = 5.49 eV Ip = 5.45 eV Ip = 5.27 eV Ip = 5.26 eV Ip = 5.35 eV Polymer Composites: Polystrene doped with TPD derivatives and C60 Polymer Composites: Polystrene doped with TPD derivatives and C60 Tuning the IP of Transport Agents

Consistent with Marcus theory for electron transfer As ionization potential of the transport agent increases, efficiency decreases IP- Dependence of Charge Generation Efficiency

Marcus Theory for Electron Transfer Hopping rate described as: λ - reorganization energy β – distance dependence

This follows the Marcus theory for electron transfer processes Dependence of Charge Generation Eff. on Distance Between Hoping Sites

Performance of All PR Materials Other Groups UAZ *P. Günter (Ed.), Nonlinear Optical Effects and Materials (Springer, NY, 2000) The dashed line connects points of equal sensitivity

Wavelength Sensitivity of PR Materials Arizona

Operation at 532 nm Samplet1t2m 32-1*25ms1.6 s0.54 ~ 45 V/µm 80-90% diffraction efficiency Fast response time (25 ms t1) * Irradiance: 1W/cm : PATPD/FDCST/TPAAc/NF (48/40.6/11.9/0.5)

Grating Recorded by Red Laser Grating Recorded by Green Laser Record two-color information of an object by writing with red and green lasers. This polymer is sensitive at both 532 and 633nm Absorption Characteristics (Two-color samples) Two-Color Sensitive Devices PATPD7DCSTECZC60 JTDA

Cool down naturally for 30s V=0 V=5kV Reading with two writing beams blocked Recording and reading at room temperature CO 2 laser beam On for 2.5-3s Thermal Fixing using CO2 Laser, 0.5mm–Glass, CW Writing CO 2 laser can provide non-contact heating

Conclusions  Optimization of Photorefractive polymers  Demonstration of PR polymers with excellent performance