Cu(In,Ga)Se2 based solar cells have reached efficiencies close to 23%. Further knowledge-driven improvements require accurate determination of the material properties. Here, we present refractive indices for all layers in Cu(In,Ga)Se2 solar cells with high efficiency. The optical bandgap of Cu(In,Ga)Se2 does not depend on the Cu content in the explored composition range, while the absorption coefficient value is primarily determined by the Cu content. An expression for the absorption spectrum is proposed, with Ga and Cu compositions as parameters. This set of parameters allows accurate device simulations to understand remaining absorption and carrier collection losses and develop strategies to improve performances.

We show that tris (8-hydroxyquinoline) aluminum (Alq3) thin films produced and characterized under ultrahigh vacuum conditions present a well-defined squared-law dependence of the injected current on the applied voltage at applied electric fields of the order of 0.25–1 MV/cm. From this, one derives an electric-field-independent electron mobility of the order of 10−7 cm2/(V s), with a variation between different samples of about one order of magnitude. Observations of current–voltage characteristics with clear indications of trap-filling and space-charge-limited conduction at high fields in Alq3 excludes the existence of traps with an exponential distribution of trap energies, as is commonly assumed in amorphous materials.

Configurationally locked polyene crystals grown in the absence and in the presence of their tailor-made auxiliaries, which are slightly modified substrate molecules, were investigated. The effects of the tailor-made auxiliaries on the crystal characteristics were investigated by X-ray crystal structure analysis and nonlinear optical and photoluminescent measurements. The substrate crystals of 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (DAT2) and 2-{3-[2-(4-pyrrolidinphenyl)-vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (PyT1) exhibit a strong powder second harmonic generation signal of about 140 and 80 times that of urea at a fundamental wavelength of 1.9 µm. Although the investigated substrate polyene molecules DAT2 and PyT1 show very similar crystal structures in the absence of auxiliaries, in the presence of the tailor-made additives with the same modification of the corresponding substrate molecules, the DAT2 crystal exhibits a morphological change and the PyT1 crystal exhibits a polymorphic change.

Amplified spontaneous emission (ASE) in single crystals of para-sexiphenyl grown in the β phase by vapor transport is demonstrated upon photoexcitation at 355nm. Excitation with femtosecond laser pulses leads to dual wavelength ASE at 427 and 450nm, while excitation with nanosecond laser pulses leads to ASE only at 450nm. The threshold fluences for nanosecond and femtosecond pumpings are determined to be 885 and 110μJ∕cm2, respectively. Additionally, the singlet exciton annihilation rate is measured to be γss=(1.2±0.1)×10−6cm3s−1.

We report growth as well as structural, optical, and charge-transport properties of highly ordered thin films of a fused thiophene derivative, 6,69-di-n-hexyl-[2,29]bi(dithieno[3,2-b:29,39d]thiophenyl) (DH-BDT). DH-BDT was synthesised with the aim of fabricating high quality, molecularly aligned thin films for organic electronic applications. Structural phase transitions are observed upon heating from room temperature, indicating the existence of three different polymorphs, denoted a, b and c. The transition temperatures are T aAb = 92 ¡ 2 uC and T bAc = 140 ¡ 2 uC. The growth of thin films of DH-BDT can be controlled to afford either the b-or the c-phase. Thermal annealing leads to the formation of large single crystalline grains with areas as large as 7 6 10 4 mm 2 . The molecules in the c-phase are cofacially aligned and show horizontally layered thin film growth. The good crystallinity and the large grain size in the c-phase lead to hole mobilities up to m c = 0.09 cm 2 V 21 s 21 , based on the measurement of space-chargelimited currents (SCLC). The b-phase consists of mutually shifted molecules, resulting in a lower hole mobility of 4.4 6 10 25 cm 2 V 21 s 21 but improving the relative luminescence quantum yield by 140% relative to that of the c-phase. Field-effect transistors of DH-BDT in the c-phase have been fabricated and yield hole mobilities which are of the same order of magnitude as the SCLC mobilities.