Since the end of the last millenium, the microelectronics industry has been facing new issues as far as CMOS devices scaling is concerned. Linear scaling will be possible in the future if new materials are introduced in CMOS device structures or if new device architectures are implemented. Innovations in the electronics history have been possible because of the strong association between devices and materials research. The demand for low voltage, low power and high performance are the great challenges for the engineering of sub 50 nm gate length CMOS devices. Functional CMOS devices in the range of 5 nm channel length have been demonstrated. The alternative architectures allowing to increase devices drivability and reduce power consumption are reviewed. The issues in the field of gate stack, channel, substrate, as well as source and drain engineering are addressed. HiK gate dielectric and metal gate are among the most strategic options to consider for power consumption and low supply voltage management. By introducing new materials (Ge, diamond/graphite carbon, HiK, ...), Si based CMOS will be scaled beyond the ITRS as the future System-on-Chip Platform integrating also new disruptive devices. For example, the association of C-diamond with HiK, as a combination for new functionalized Buried Insulators, will bring new ways of improving short channel effects and suppress self-heating. Because of the low parasitics required to obtain high performance circuits, alternative devices will hardly compete against logic CMOS.

Trap parameters in poly(1-(3,4-difluorophenyl)-2-(4-pentylcyclohexylphenyl)acetylene) (PDPA-2F) based devices have been investigated by using the thermally stimulated current (TSC) technique. The device structure is ITO-PEDOT-(PDPA-2F)-M, where M stands for the cathode metal (Al, Ca/Al, and Au). The results reveal at least three TSC peaks in devices denoted as peaks A, B and C. Comparing trap parameters in ITO-PEDOT-(PDPA-2F)-Au hole-only device and ITO-PEDOT-(PDPA-2F)-Ca Al (Al) bipolar devices, we assigned A and B trap types to hole-like traps and C type traps to electron-like traps. The trap densities are in the range of 1015−1017 cm−3 and the trap levels are 0.12 eV (A type traps), 0.36 eV (B type traps), and 0.25 eV (C type traps).

In this work low bandgap thienylenevinylene and phenylene vinylene copolymers, which possess either 3,4-ethylenedioxylthiophene (EDOT) groups (Polymer 1) or long alkyl side chains (Polymer 2) were investigated and compared in photoinduced electron transfer properties and photovoltaic performance. The results show that the interaction of the photoexcited polymers with an electron acceptor ([6,6]-phenyl C61 – butyric acid methyl ester (PCBM)) leads to charge generation and transfer for both polymers. We found that the long alkyl side chain in Polymer 2 instead of the EDOT group in Polymer 1 enhances the open circuit voltage ( $V_{\it OC})$ but lowers the short circuit current ( $I_{\it SC})$ . On the other hand the long alkyl side chain in Polymer 2 significantly improves the solubility and enhances processability for solar cells fabrication. Optimization of the chemical structure of these low bandgap polymers could lead to a spectral improvement of photocurrent generation in organic solar cells.

We have fabricated heterojunction solar cells comprising active layers of perylene diimide (PDI) or perylene bisbenzimidazole (CONPER, conjugated perylene dye) as electron acceptor and ZnPC as donor. Bilayer solar cells were produced by successive evaporation of zinc phthalocyanine (ZnPC) and perylene diimide (PDI) or perylene bisbenzimidazole (CONPER) on glass substrates coated with indium doped tin oxide. Active layers with different thickness were evaporated. The bilayer cells were characterized under simulated AM 1.5 illumination (100 mW/cm2). The best results were obtained for the device structure of ITO/PEDOT/ZnPC (40 nm)/perylene bisbenzimidazole (60 nm)/Al (70 nm).

Hybrid concepts based on a nanoscale combination of organic and inorganic semiconductors are a promising way to enhance the cost efficiency of solar cells through a better use of the solar spectrum, a higher aspect ratio of the interface, and the good processability of polymers.A new type of solar cells has been investigated. It is based on a heterojunction between regio-regular poly(3-hexylthiophene) as an organic electron donor and silicon as an inorganic electron acceptor. In a first step towards nano-structured devices, cells made of flat thin films of these materials have been studied as a model case of the heterojunction.The materials were characterized through ellipsometry and absorption spectroscopy. The devices were studied by means of their spectral response and their I-V characteristics. By combining these results, the contribution of each layer and the mechanisms of photocurrent generation are explained.The best cells to-date show a power conversion efficiency of 1.6% under AM 1.5 illumination, with a V oc of 0.704 V and a J sc of 4.22 mA/cm2.

This paper presents the application of manganese dioxide to electromagnetic wave absorber. The effective permittivity was calculated by modified Rayleigh mixing formula, and the electromagnetic wave absorbing properties of composites with different volume fractions of manganese dioxide were investigated by the comparison of calculated and experimental values in 2–12 GHz frequencies. It is found that the pure manganese dioxide holds a high dielectric constant, which is a function of frequency. The manganese dioxide composites show high absorbing performance in low frequencies, and the calculated electromagnetic properties fit the experimental values for large volume fractions used in this study.

We present a series of organic photovoltaic (PV) cells based on the bulk-distributed heterojunction where $\pi $ -conjugated polymer poly[1-(4-trimethylsilylphenyl)-2-phenylvinylene], PSDPhV, acts as the donor upon photoexcitation and the substituted perylene based low-molecular-weight compound: N,N`-di(pent-3-yl)-perylene-3,4:9,10-bis(dicarboximide), DPe-PTCDI, as the acceptor of photogenerated electrons. According to both absorption spectra and AFM images of the thin films spin-coated from solution of DPe-PTCDI and PSDPhV in toluene, the DPe-PTCDI is molecularly dissolved in conjugated polymer matrix. Upon exposition of layers to toluene vapors, microcrystals of DPe-PTCDI are progressively formed. The influence of the morphology of DPe-PTCDI inside the polymer matrix on PV cell performance is investigated.

The synthesis and properties of two semiconducting donor-acceptor (D-A) block copolymers and their application in nanostructured bulk heterojunction solar cells are reported. The donor segments were obtained via nitroxide mediated polymerization of either bis(4-methoxyphenyl)-4'-vinylphenylamine or N,N'-bis(4-methoxyphenyl)-N-phenyl-N'-4-vinylphenyl-[1,1'biphenyl]-4,4'-diamine. Narrow-distributed macroinitiators, poly{bis(4-methoxyphenyl)-4'-vinylphenylamine} (PvDMTPA) and poly{N,N'-bis(4-methoxyphenyl)-N-phenyl-N'-4-vinylphenyl-[1,1'biphenyl]-4,4'-diamine} (PvDMTPD) were used to polymerize the acceptor monomer perylene diimide acrylate (PerAcr) to yield block copolymers with well-defined molecular weights. Different diblock copolymers, PvDMTPA-block-PPerAcr and PvDMTPD-block-PPerAcr, with high perylene diimide weight fractions were prepared. The block copolymers exhibited efficient fluorescence quenching. Transmission electron microscopy revealed wire-like and worm-like nanostructures throughout bulk samples. Thin film photovoltaic devices showed short circuit currents $J_{\it SC}$ of up to 1.21 mA/cm2 and power conversion efficiencies ηof 0.32% under AM 1.5 illumination conditions.

The nanoscale morphology of the active layer in bulk-heterojunction solar cells consisting of regioregular poly(3-hexylthiophene-2, 5-diyl) (P3HT) and methanofullerene([6-6]-phenyl C61 butyric acid methyl ester) (PCBM) was extensively studied using Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and optical microscopy. Different weight ratios of P3HT:PCBM were investigated as a function of annealing temperature and time revealing the occurrence of crystallization of both components. Firstly, the as-prepared films can be described as a semi-crystalline blend. Secondly, it has been demonstrated that for a short annealing time (5 min) at lower annealing temperatures (75–115 °C) an increased crystallization of P3HT occurs. Thirdly, it has been observed that a prolonged annealing at the given temperature range or a short annealing at higher temperatures (≥ 120 °C) leads to the formation of a new ordered crystalline structure of PCBM. These new ordered structures, a few μm up to 100 μm in length, form a network of needle-like and even fan-shaped crystals. Key-parameters to “tune” this new ordered structure of PCBM are blend ratio and annealing conditions. The growth mechanism of these new PCBM-structures is described by means of diffusion.

High conductive and transparent thin films based on carbon nanotube – poly(3,4-ethylene-dioxythiophene)-poly(styrene sulfonate), PEDOT-PSS blends have been used to replace the conventional indium tin oxide (ITO) as the hole collecting electrode in organic photovoltaic cells. Using PEDOT:PSS as the host material, excellent dispersion of functionalized single wall carbon nanotubes can be achieved enhancing the polymer's conductivity, while maintaining its excellent optical transparency. Photovoltaic cells with Poly(3-hexylthiophene), P3HT and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM as the electron donor and acceptor on respectively on polymer-nanotube substrates have been fabricated and characterized. A power conversion efficiency of 1.3%, with a fill factor of 0.4, an open-circuit voltage of 0.6 V and a short-circuit current of 5.6 mA/cm2 under 100 mW/cm2 white light illumination are reported. These values are close with the reference cells made on ITO glass substrates with the same device structure and fabrication process. The only drawback is on the fill factor which is considerably smaller due to the high resistance of the polymer-nanotube film. Nevertheless, the results indicate that the spin casted polymer-nanotubes thin films are a low cost alternative to ITO for organic electronics.

CdSe nanocrystals were modified with small ligand molecules in order to render them compatible with a conducting polymer matrix. Modified NCs were characterized by NMR, optical spectroscopy, electrochemistry. Hybrid materials based on such modified nanocrystals and a conducting polymer (MDMO-PPV, P3HT or P3OT) were prepared, characterized, and tested in photovoltaic devices. Modified NCs quench the polymer PL in solutions as well as in films. Photovoltaic devices display modest power conversion efficiencies mainly due to phase segregation.

In this paper, we consider the two-gap Ginzburg-Landau (G-L) free energy functional including the interactions, and obtain a very simple and explicit formula which presents the relation between the critical current density and temperature. The result shows that the temperature dependence of critical current density of a two-gap superconductor is of the form J c ∝ (T c * − T)1/2 at low temperatures and J c ∝ (T c * − T)3/2 near the critical temperature. Our critical current density expression is in accord with the previous theoretical work and experimental data.

A method has been developed to link the geometry of the trapped charge distribution within irradiated insulators to the mirror plot shape, in a scanning electron microscope. We give a detailed analysis of the geometrical optic approximation which is used to evaluate the mirror image formation. We establish then analytical mirror relations obtained for diverse trapped charge distributions such as homoïdal charge distribution, bipunctual and cylindrical ones. Knowledge of the charge distribution first moments enables us to investigate then their effect on the first terms of the mirror expression limited development. Finally, we apply these analytical expressions to evaluate certain characteristics of the charge distribution from an experimental mirror plot.

Sub-bandgap absorption features ( $\alpha \le 100$  cm−1) have been detected in organic and inorganic semiconductors and their heterojunctions. Photothermal deflection spectroscopy (PDS) is used to increase the detection limit considerably with respect to common absorption spectroscopy. Results are presented on discotic liquid crystals, donor-acceptor complex formation in P3HT:PCBM solar cells and UV-induced defect generation in nanoporous $\mathrm{TiO_2}$ .

Efficient charge transfer between a newly synthesizedlow band gap (LBG) conjugated polymer and the C60 derivativePCBM is demonstrated. Spectral and time-resolved photoluminescence(PL) measurements show strong quenching and charge separation inthe picosecond time range. The charge transfer is furtherconfirmed by light-induced electron paramagnetic resonance (EPR)measurements of both the positive polarons and the fullereneradicals, which can be resolved in high-frequency EPR. Thepotential for the LBG polymer to act as acceptor was examined inblends with the para-phenylene-vinylene polymer MDMO-PPV. Nocharge transfer, but instead energy transfer from MDMO-PPV to LBGoccurs in these blends, as shown by PL spectroscopy.

Single planar heterojunction organic solar cells based on CuPc-C60 small molecule active layer have been optimised using ITO anode electrode obtained by ion beam sputtering (IBS). The main interests in IBS process is an easy control of layer thickness and light transmission, and a better roughness of the anode compared to commercially available ITO, which can allow a PEDOT-PSS layer thickness optimisation.Comparison of two identical solar cells with commercially available ITO and our ITO obtained by IBS leads to a power conversion efficiency enhancement from 0.5% to 0.7%. Surprisingly, decreasing the serial resistance by increasing ITO thickness does not lead to further improvements, and this feature has been attributed to an increase of the ITO absorption and a possible cathode breaking due to a too thick cell structure. Better roughness of our ITO has permitted to decrease the PEDOT-PSS layer thickness, leading to an enhancement of the power conversion efficiency up to 1.3%. Optimising the cathode by adding an exciton blocking layer (BCP or LiF) has allowed us to decrease the active layer thickness, leading to a decrease of the cell serial resistance and giving rise to near 1.9% power conversion efficiency.

Chlorobenzene cast films of poly(3-hexylthiophene)-blend-[6,6]-phenyl C61 butyric acid methyl ester (P3HT-blend-PCBM) in 1:1 ratios were used in photovoltaic cells with the structure glass/ITO/PEDOT-blend-PSS/P3HT-blend-PCBM/LiF/Al. By varying the molecular weights of the P3HTs from 4500 to 280 000 g mol−1, it was found that P3HT molecular weight distributions had an important impact on cell characteristics and the most effective annealing temperature required.

Novel dyads containing [60]fullerene–perylenediimide units were developed as light-harvesting acceptors for the preparation of efficient solar cells. The antenna was grafted onto C60 with the aim to improve the absorption spectrum of materials used in bulk-heterojunction devices. Electrochemical and photophysical studies of these dyads in solution have revealed that there was no significant ground-state electronic interaction between the covalently bonded PDI and fullerene moieties. Steady-state fluorescence experiments evidenced an effective photoinduced energy transfer from the PDI moiety to C60. The potential use of these light-harvesting fullerenes in organic solar cells was estimated with their incorporation in bulk-heterojunctions using poly(3-hexylthiophene) as the conjugated $\pi $ -donor polymer.

In spite of the high potential of polymer photovoltaic (PV) cells, considerable improvement of their stability under operational conditions needs to be achieved. The few published data on the stability of such cells are devoted to accelerated indoor testing at elevated temperatures. The acceleration factor is undoubtedly dependent on the PV materials, the cell architecture and may vary with the degradation. We report preliminary results of long-term evaluation of PV performance of polymer cells under real sun operational conditions. The studied devices include three types of encapsulated polymer/fullerene cells which differed by the configuration and content of the photoactive layer: (1) bulk heterojunction of MEH-PPV:PCBM; (2) bulk heterojunction of P3HT:PCBM; (3) bilayer heterojunction P3CT-C60. The MEHPPV-PCBM cell exhibited the fastest degradation. The degradation of PV performance of the P3HT-PCBM cell was much slower while the P3CT-C60 device was found to be the most stable. Effect of restoration of I sc and V oc was found when the P3HT-PCBM and P3CT-C60 cells were kept in the dark overnight. The first I sc and V oc measurements every morning yielded the highest values compared to those during the rest of a day. While I sc recovered only partly and exhibited significant degradation during a month, V oc values recovered completely every night and showed almost no reduction on a long-term time scale.