Evidence for photoinduced electron transfer from the excited state of a conducting polymer onto buckminsterfullerene, C(60), is reported. After photo-excitation of the conjugated polymer with light of energy greater than the pi-pi* gap, an electron transfer to the C(60) molecule is initiated. Photoinduced optical absorption studies demonstrate a different excitation spectrum for the composite as compared to the separate components, consistent with photo-excited charge transfer. A photoinduced electron spin resonance signal exhibits signatures of both the conducting polymer cation and the C(60) anion. Because the photoluminescence in the conducting polymer is quenched by interaction with C(60), the data imply that charge transfer from the excited state occurs on a picosecond time scale. The charge-separated state in composite films is metastable at low temperatures.

https://science.sciencemag.org/content/sci/258/5087/1474.full.pdf

Photoinduced electron transfer from a conducting polymer to buckminsterfullerene.

A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

When asked to explain the importance of the discovery of conducting polymers, I offer two basic answers: first they did not (could not?) exist, and second, that they offer a unique combination of properties not available from any other known materials. The first expresses an intellectual challenge; the second expresses a promise for utility in a wide variety of applications.

Semiconducting and Metallic Polymers: The Fourth Generation of Polymeric Materials (Nobel Lecture).

In this paper it is demonstrated that the characteristics of light‐emitting diodes based upon MEH‐PPV [more fully known as poly(2‐methoxy,5‐(2’‐ethyl‐hexoxy)‐1,4‐phenylene‐ vinylene)] are determined by tunneling of both the holes and the electrons through interface barriers caused by the band offset between the polymer and the electrodes. It is shown that manipulating these offsets can control the useful operating voltage of the device as well as its efficiency. A model is developed that clearly explains the device characteristics of a wide range of diodes based upon MEH‐PPV. The turn‐on voltage for an ideal device is shown to be equal to the band gap, i.e., 2.1 eV for MEH‐PPV, and is slightly lower at 1.8 eV for an indium‐tin oxide/MEH‐PPV/Ca device. If there is a significant difference in the barrier height, the smaller of the two barriers controls the I–V characteristics, while the larger barrier determines the device efficiency. In indium‐tin‐oxide/MEH‐PPV/Ca devices, the barrier to hole injection is ...

Carrier tunneling and device characteristics in polymer light‐emitting diodes

Counter-ion induced processibility of conducting polyaniline and of conducting polyblends of polyaniline in bulk polymers

Enhanced order and electronic delocalization in conjugated polymers oriented by gel processing in polyethylene.

Analyse de la conductivite infra-rouge photoinduite, fonction de la frequence, obtenue a partir des mesures d'absorption photoinduites des ces isolants. On part de la theorie du transport des polarons non adiabatiques. La conductivite calculee est en bon accord avec la conductivite experimentale dans l'infra-rouge moyen dans les supraconducteurs et dans les dielectriques «parents», les porteurs sont des polarons habilles avec un nuage de polarisation de phonons

Application of the polaron-transport theory to σ(ω) in Tl 2 Ba 2 Ca 1-x Gd x Cu 2 O 8 , YBa 2 Cu 3 O 7-δ , and La 2-x Sr x CuO 4

We have studied the vibrational and electronic structure and the elementary charged excitations of poly(1,4-phenylene-vinylene) and a series of its (2,5-alkoxy) derivatives including poly(2,5-methoxy-PV), poly(2,5-hexoxy-PV), poly(2,5-octoxy-PV), and poly[2-methoxy,5-(2'ethyl-hexoxy)-PV] by absorption, photoinduced (PI) absorption, and doping-induced (DI) absorption. For the pristine materials, we observe that the band gap decreases by as much as \ensuremath{\sim}0.3 eV with the introduction of alkoxy side chains. We assign the observed ir-active phonons to specific structural vibrations. Upon either PI or DI carrier injection, we observe a series of infrared-active vibrational (IRAV) modes and two subgap electronic absorptions that we associate with the formation of bipolarons. Assignment of the IRAV modes indicates that the charged bipolarons couple strongly to lattice modes of the polymer backbone, and the measured IRAV mode frequencies indicate that the pinning strength of bipolarons in a given system decreases as the length of the side chain increases. In addition, from the energy of the two subgap electronic absorptions, we determine that the confinement parameter \ensuremath{\gamma} increases, the Coulomb interaction energy ${\mathit{U}}_{\mathit{b}}$ remains unchanged, and the Coulomb binding energy ${\mathit{E}}_{\mathit{b}}$ decreases with side-chain length.

Substitution effects on bipolarons in alkoxy derivatives of poly(1,4-phenylene-vinylene).

Comparison of photoinduced local modes (PILM's) of insulating ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.3}$ and ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Ca}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Gd}}_{\mathit{x}}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8}$ with Raman spectra of their metallic counterparts suggests that carrier injection anomalously increases the frequencies of phonons involving z-axis apex-oxygen motion in both the dilute (insulator) and concentrated (metallic) limit. In ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$, we observe PILM's whose frequencies suggest a correspondence with the ``ghost modes'' observed in neutron scattering [Rietschel et al., Physica C 162--164, 1705 (1989)]. These data, together with Raman data on apex-oxygen anharmonicity, enable us to discuss the vibronic mode couplings involved in polaron formation in the three materials.

Anomalous shifts of oxygen-mode frequencies in La 2-x Sr x CuO 4 , YBa 2 Cu 3 O 7-δ and Tl 2 Ba 2 Ca 1-x Gd x Cu 2 O 8 studied by photoinduced infrared absorption and Raman spectroscopy

K. F. Voss

Papers

Enhanced order and electronic delocalization in conjugated polymers oriented by gel processing in polyethylene.

Application of the polaron-transport theory to σ(ω) in Tl 2 Ba 2 Ca 1-x Gd x Cu 2 O 8 , YBa 2 Cu 3 O 7-δ , and La 2-x Sr x CuO 4

Substitution effects on bipolarons in alkoxy derivatives of poly(1,4-phenylene-vinylene).

Anomalous shifts of oxygen-mode frequencies in La 2-x Sr x CuO 4 , YBa 2 Cu 3 O 7-δ and Tl 2 Ba 2 Ca 1-x Gd x Cu 2 O 8 studied by photoinduced infrared absorption and Raman spectroscopy

Infrared reflection of epitaxial tl2ba2cacu2o8 thin films in the normal and superconducting states