The cost of photovoltaic power can be reduced with organic solar concentrators. These are planar waveguides with a thin-film organic coating on the face and inorganic solar cells attached to the edges. Light is absorbed by the coating and reemitted into waveguide modes for collection by the solar cells. We report single- and tandem-waveguide organic solar concentrators with quantum efficiencies exceeding 50% and projected power conversion efficiencies as high as 6.8%. The exploitation of near-field energy transfer, solid-state solvation, and phosphorescence enables 10-fold increases in the power obtained from photovoltaic cells, without the need for solar tracking.

Organic vapor phase deposition was used to grow polycrystalline pentacene channel thin-film transistors. Substrate temperature, chamber pressure during film deposition, and growth rate were used to vary the crystalline grain size of pentacene films on O2-plasma treated SiO2 from 0.2 to 5 μm, leading to room-temperature saturation regime field-effect hole mobilities (μeff) from 0.05±0.02 to 0.5±0.1 cm2/V s, respectively. Surface treatment of SiO2 with octadecyltrichlorosilane (OTS) prior to pentacene deposition resulted in μeff⩽1.6 cm2/V s, and drain current on/off ratios of ⩽108 at room temperature, while dramatically reducing the average grain size. X-ray diffraction studies indicate that the OTS treatment decreases the order of the molecular stacks. This suggests an increased density of flat-lying molecules, accompanying the improvement of the hole mobility at the pentacene/OTS interface.

Solar concentrators can significantly reduce the use of expensive semiconductor materials in photovoltaic (PV) energy conversion. Luminescent solar concentrators (LSCs) are especially promising because they do not need to track the sun to obtain high optical concentration factors. [1][2][3][4][5][6] In this work, we demonstrate LSCs employing phycobilisomes, which are photosynthetic antenna complexes that concentrate excited states in red algae and cyanobacteria. [7,8] The phycobilisomes are cast in a solid-state matrix that preserves their internal Förster energy-transfer pathways and large wavelength shift between absorption and emission. Casting is a simple fabrication technique that also eliminates any need for expensive high-index glass or plastic. By comparing the performance of intact and partly decoupled complexes, we establish that energy transfer within intact phycobilisomes reduces LSC self-absorption losses by approximately (48 AE 5)%. These results suggest that phycobilisomes are a model for a new generation of cast LSCs with improved efficiency at high optical concentrations.LSCs are nontracking concentrators that redirect solar radiation into simple slab waveguides (see Fig. 1a). Light incident on an LSC is absorbed by dyes, re-emitted into a guided mode in the slab, and finally collected by a PV cell mounted at the edge of the slab. The maximum optical concentration of an LSC is theoretically limited by the wavelength shift between absorption and emission in the dye.[9] Larger wavelength shifts reduce the re-absorption of radiation already emitted into the LSC waveguide, [10,11] and alleviate compounding losses if either the photoluminescence efficiency of the dye, h PL , or the fraction of emitted light trapped in the waveguide, h trap , is less than unity.

The performance of a phthalocyanine-based photovoltaic is boosted in the absorption gap between the phthalocyanine Q and Soret bands. Light absorption is decoupled from exciton diffusion using a light absorbing "antenna" layer external to the conventional charge generating layers. Radiation absorbed by the antenna is transferred into the charge generating layers via surface plasmon polaritons in an interfacial thin silver contact. The peak efficiency of energy transfer is measured to be at least ͑51± 10͒%.

The authors demonstrate that thin film organic photovoltaic cells are efficient detectors of surface plasmon polaritons ͑SPPs͒. For = 532 nm radiation in a Kretschmann configuration, the external quantum efficiency in fullerene-copper phthalocyanine photovoltaic cells is doubled at resonance to 12%. In thin heterojunction organic photovoltaics, SPP detection relies on a substantial increase in absorption when the incoming radiation is coupled to guided SPPs rather than unguided photons. SPP scattering and nonradiative losses are negligible; however, optical modeling shows that cathode metal penetration into the neighboring organic semiconductor is a major source of loss for SPP or photonic excitation.