Record high efficiencies for a polymer‐based solar cell are reported here for an inorganic/organic composite photovoltaic device containing a single polymer film rather than a polymer/polymer or polymer/nanoparticle blend. The high efficiencies are reported to be due to device construction (see Figure) and the electronic properties of the phenylamino‐p‐phenylenevinylene‐based polymer used.

By studying the photoluminescence emission and photovoltaic properties of blends of polyphenylenevinylene (PPV)-based electron donating and accepting polymers, the authors observed a strict anticorrelation between relative exciplex emission in the solid state and photovoltaic efficiency of corresponding blend devices. Comparative studies on defined bilayer geometries showed that the overall shape of the current-voltage characteristics under illumination is independent of device geometry and layer thickness. Consequently, they conclude that the photocurrent in PPV-based blends is mainly determined by the efficiency to form free carriers rather than by free carrier recombination.

Thin-film small molecule/polymer hybrid bilayer photovoltaic cells have been constructed, exhibiting power conversion efficiencies of 0.71% under 80 mW/cm2 white light illumination. The parameters influencing the photovoltage of these devices are explored by reversing the order of the photoactive layers while maintaining the same electrode configuration. It has been found that the properties of the organic photoactive layers play an important role in determining the direction of current flow and the photovoltage of the device. Comparison is made to analogous pure small molecule bilayer devices, and conclusions about some of the factors influencing device efficiency are drawn. It has been shown that ordering of the band offsets of the two organic materials plays an important role in determining the polarity of the photocurrent and the photovoltage of the device.

We have studied thin films of the conjugated polymer poly[2-methoxy-5-(2‘-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), prepared from polymer samples whose weight-average molecular weight (M w) was varied in the broad range of 10−1600 kg/mol. Anisotropic refractive index measurements by means of waveguide prism coupling and reflectometry as well as polarized infrared spectroscopy were used to analyze the polymer chain orientation in the films. We found that the film morphology depends significantly on the molecular weight, especially in the range M w < 400 kg/mol. Thin films of high molecular weight MEH-PPV have most polymer chain segments oriented parallel to the film planein contrast to low molecular weight samples which have nearly random orientation of the chain segments. Appropriate choice of molecular weight enables fine-tuning of the refractive index of slab waveguides and reduction of their mode propagation losses to less than 1 dB/cm.

Among the various applications for reversible holographic storage media, a particularly interesting one is time-gated holographic imaging (TGHI). This technique could provide a noninvasive medical diagnosis tool, related to optical coherence tomography. In this technique, biological samples are illuminated within their transparency window with near-infrared light, and information about subsurface features is obtained by a detection method that distinguishes between reflected photons originating from a certain depth and those scattered from various depths. Such an application requires reversible holographic storage media with very high sensitivity in the near-infrared. Photorefractive materials, in particular certain amorphous organic systems, are in principle promising candidate media, but their sensitivity has so far been too low, mainly owing to their long response times in the near-infrared. Here we introduce an organic photorefractive material -- a composite based on the poly(arylene vinylene) copolymer TPD-PPV -- that exhibits favourable near-infrared characteristics. We show that pre-illumination of this material at a shorter wavelength before holographic recording improves the response time by a factor of 40. This process was found to be reversible. We demonstrate multiple holographic recording with this technique at video rate under practical conditions.