The production of strings (disclination lines and loops) has been observed by means the Kibble mechanism domain (bubble) formation in isotropic-nematic phase transition uniaxial nematic liquid crystal 4-cyano-4'-n-pentylbiphenyl. number formed per bubble is about 0.6. This value reasonable agreement with a numerical simulation experiment which used for order parameter space crystal.

We report transient photocurrent measurements on solar cell structures based dye-sensitized, porous TiO2 films filled with a liquid electrolyte. The are interpreted as ambipolar diffusion; under most measurement conditions, the diffusion coefficient is dominated by electrons diffusing in matrix. strong dependence of upon photoexcitation density, has been proposed previously. coefficients vary from 10-8 cm2 s-1 at low density to 10-4 for densities 1018 cm-3. At specified measured using weak...

We propose an experimental procedure for testing the Einstein relation carrier drift and diffusion in semiconductors exhibiting non-Gaussian or dispersive transport. present corresponding hole time-of-flight steady-state photocarrier grating measurements hydrogenated amorphous silicon ( $a\ensuremath{-}\mathrm{S}\mathrm{i}:\mathrm{H}$). For a range of mobilities ${10}^{\ensuremath{-}5}--{10}^{\ensuremath{-}2}\mathrm{cm}{}^{2}/\mathrm{V}\mathrm{s}$ we find that our estimates are approximately...

We report nanosecond domain time-of-flight measurements of electron and hole photocarriers in methylammonium lead iodide perovskite solar cells. The mobilities ranged from 0.06 to 1.4 cm2/Vs at room temperature, but there is little systematic difference between the two carriers. also find that drift are dispersive (time-dependent). dispersion parameters range 0.4–0.7, they imply terahertz will be much larger than mobilities. temperature-dependences consistent with confinement transport...

The temperature and photoexcitation density dependences of the electron transport dynamics in electrolyte-filled mesoporous ${\mathrm{TiO}}_{2}$ nanoparticle films were investigated by transient photocurrent measurements. thermal activation energy diffusion coefficient photogenerated electrons ranged from 0.19--0.27 eV, depending on specific sample studied. also depends strongly density; however, has little, if any, dependence density. light intensity can be used to infer...

We propose a hydrogen-mediated model for defect metastability in hydrogenated amorphous silicon which associates the creation of paramagnetic defects with transfer hydrogen between dilute and clustered phases bonded hydrogen. Hydrogen phase is predominantly paired on sites we identify as weak Si-Si bonds when unhydrogenated. An elementary statistical-mechanics calculation based this accounts observed thermally activated density also rationalizes changes spin following electron irradiation evolution.

We present intensity-modulated photocurrent and infrared transmittance measurements on dye-sensitized solar cells based a mesoporous titania (TiO2) matrix immersed in an iodine-based electrolyte. Under short-circuit conditions, we show that elementary analysis accurately relates the two measurements. open-circuit transmittance, photovoltage yield information characteristic depth at which electrons recombine with ions (the “locus of recombination”). For one particular series samples...

An organic-inorganic hybrid solar cell with a p-i-n stack structure has been investigated. The p-layer was spin coated film of PEDOT:PSS [poly(3,4-ethylenedioxythiophene) poly (styrenesulfonate)]. i-layer hydrogenated amorphous silicon (a-Si:H), and the n-layer microcrystalline (μc-Si). inorganic layers were deposited on top organic layer by hot-wire chemical vapor deposition technique at 200°C. These devices exhibited open circuit voltages (VOC) as large 0.88V conversion efficiencies 2.1%....

Organic/inorganic heterojunction solar cells were fabricated on the (100) face of n-type silicon crystals using acid-doped polyaniline (PANI) with widely varying conductivities. For films conductivities below 10−1S∕cm, open-circuit voltage VOC increases increasing film conductivity as expected when is limited by work function film. Extrapolation these results to higher indicates that PANI could support 0.7V or larger. measurements for saturated at 0.51V. We speculate uncontrolled surface...

The theory of trap-controlled dispersive transport based on exponential band-tail traps is extended to include the saturation trap occupancy at high excitation levels. absence effects in transient photocurrent experiment Hvam and Brodsky shown contradict hypothesis this model.

We calculate the maximum optical absorptance enhancements in thin semiconductor films on metals due to structures that diffuse light and couple it surface plasmon polaritons. The calculations can be used estimate plasmonic effects light-trapping solar cells. are based statistical distribution of energy electromagnetic modes structure, which include polariton at metal interface as well trapped waveguide film. enhancement has form 4n2+nλ/h (n – film refractive index, λ wavelength, h...

We have measured the temperature dependence of electron drift mobility using time-of-flight technique for a series undoped hydrogenated amorphous silicon-germanium alloys with band gaps spanning range 1.47--1.72 eV. also developed techniques analyzing dispersion effects in such measurements, which permitted us to compare essentially all previous measurements our own. draw two main conclusions. First, there is substantial agreement between laboratories reduction due Ge alloying. Second, we...

A grossly inhomogeneous, noncolumnar morphology has been observed in doped, plasma-deposited hydrogenated amorphous silicon (a-Si:H) within critical ranges of the diborane to silane ratio gas phase. The level can be as low 5 ppm and depends both on electrode self-bias potential growth rate. Undoped specimens prepared under same deposition conditions have properties typical device-grade a-Si:H. These observations suggest a structural origin for some doping-dependent

We report electron and hole drift mobilities in thin film polycrystalline CdTe solar cells based on photocarrier time-of-flight measurements. For a deposition process similar to that used for high-efficiency cells, the are range of 10−1–100 cm2/V s, holes 100–101 s. The about thousand times smaller than those measured single crystal with time-of-flight; ten smaller. Cells were examined before after vapor phase treatment CdCl2; had little effect mobility, but decreased mobility. able exclude...

Experimental evidence for two regimes in the relationship of defect density to hydrogenation state hydrogenated amorphous silicon (a-Si:H) is presented. A prevoius model based on phases bound hydrogen a-Si:H shown account measured relationship.

We have measured transient photocurrents on several p-i-n solar cells based microcrystalline silicon. For two of these samples, we were able to obtain conclusive hole drift-mobility measurements. Despite the predominant crystallinity temperature-dependent measurements consistent with an exponential-bandtail trapping model for transport, which is usually associated noncrystalline materials. estimated valence bandtail widths about 31meV and band mobilities 1–2cm2∕Vs. The support mobility-edge...

We present temperature-dependent measurements and modeling for a thickness series of hydrogenated amorphous silicon nip solar cells. The comparison indicates that the maximum power density (PMAX) from as-deposited cells has achieved hole-mobility limit established by valence bandtail trapping, PMAX is thus not significantly limited intrinsic-layer dangling bonds or doped layers interfaces. Measurements properties light-soaked show converge below 250 K; model perturbing band tail traps with...

We present a new perspective on defect levels in hydrogenated amorphous silicon (a-Si:H) that unifies relaxation effects inferred from two recent experiments. In particular, we show how earlier calculations of dangling-bond can account for both the level deepening effect reported transient capacitance measurements and shallowing photocurrent under optical bias. The former is due to toward pyramidal bonding configuration, latter planar configuration. comment many-body nature remarkably slow...

Abstract The transient response of an illuminated (‘optically biased’) semiconductor to a small photoexcitation impulse is calculated by linearizing the multiple-trapping model. Both photocurrent and photo-induced absorption responses are treated, including effects finite trap occupancy monomolecular or bimolecular recombination processes. Specific solutions presented for exponentially distributed traps, simple classification these based on thermalization criterion advanced. numerical...

We report photocarrier time-of-flight measurements of electron drift mobilities for the p-type CuIn1−xGaxSe2 films incorporated in solar cells. The range from 0.02 to 0.05 cm2/Vs and are weakly temperature-dependent 100–300 K. These values lower than Hall (2-1100 cm2/Vs) reported n-type polycrystalline thin single crystals. propose that properties disorder-induced mobility edges discuss how this disorder could increase cell efficiencies.