Organic photodetectors are interesting for low cost, large area optical sensing applications. Combining organic semiconductors with discrete absorption bands outside the visible wavelength range with transparent and conductive electrodes allows for the fabrication of visibly transparent photodetectors. Visibly transparent photodetectors can have far reaching impact in a number of areas including smart displays, window-integrated electronic circuits and sensors. Here, we demonstrate a near-infrared sensitive, visibly transparent organic photodetector with a very high average visible transmittance of 68.9%. The transmitted light of the photodetector under solar irradiation exhibits excellent transparency colour perception and rendering capabilities. At a wavelength of 850 nm and at −1 V bias, the photoconversion efficiency is 17% and the specific detectivity is 1012 Jones. Large area photodetectors with an area of 1.6 cm2 are demonstrated.

A method to exchange the counterion of cyanine dyes to Δ-TRISPHAT(-) and PF6(-) is presented. The influence of these counterions on the photophysical and electrochemical properties of the cyanine dye in solution is discussed, and tendencies in the solid packing are highlighted by X-ray crystal structures. The compounds were applied in semitransparent bilayer organic solar cells together with C60, and a power conversion efficiency of 2.2% was achieved while maintaining a high transparency level in the visible region of 66%.

Efficient light detection in the near-infrared (NIR) wavelength region is central to emerging applications such as medical imaging and machine vision. An organic upconverter (OUC) consists of a NIR-sensitive organic photodetector (OPD) and an visible organic light-emitting diode (OLED), connected in series. The device converts NIR light directly to visible light, allowing imaging of a NIR scene in the visible. Here, we present an OUC composed of a NIR-selective squaraine dye-based OPD and a fluorescent OLED. The OPD has a peak sensitivity at 980 nm and an internal photon-to-current conversion efficiency of ∼100%. The OUC conversion efficiency (0.27%) of NIR to visible light is close to the expected maximum. The materials of the OUC multilayer stack absorb very little light in the visible wavelength range. In combination with an optimized semitransparent metal top electrode, this enabled the fabrication of transparent OUCs with an average visible transmittance of 65% and a peak transmittance of 80% at 620 nm. Visibly transparent OUCs are interesting for window-integrated electronic circuits or imaging systems that allow for the simultaneous detection of directly transmitted visible and NIR upconverted light.

Cyanine dyes are fluorescent organic salts with intrinsic conductivity for ionic and electronic charges. Recently ( J. Am. Chem. Soc. 2013 , 135 , 18008 - 18011 ), these features have been exploited in cyanine light-emitting electrochemical cells (LECs). Here, we demonstrate that stacked, constant-voltage driven trimethine cyanine LECs with various counteranions develop a p-i-n junction that is composed of p- and n-doped zones and an intrinsic region where light-emission occurs. We introduce a method that combines spectral photocurrent response measurements with optical modeling and find that at maximum current the intrinsic region is centered at ∼37% away from the anode. Transient capacitance, photoluminescence and attenuance experiments indicate a device situation with a narrow p-doped region, an undoped region that occupies ∼72% of the dye layer thickness and an n-doped region with a maximum doping concentration of 0.08 dopant/cyanine molecule. Finally, we observe that during device relaxation the parent cyanines are not reformed. We ascribe this to irreversible reactions between doped cyanine radicals. For sterically conservative cyanine dyes, this suggests that undesired radical decomposition pathways limit the LEC long-term stability in general.

a b s t r a c tPerovskite solar cells have attracted attention due its high conversion efficiency and low cost. In this work, Nb 2 O 5 is used as an alternative compact hole blocking layer in conjunction with mesoporous TiO 2 and CH 3 NH 3 PbI 3 in perovskite solar cells. The influence of Nb 2 O 5 layer thickness was studied and it was found to strongly influence the J-V hysteresis of the cells. Devices constructed with 50 nm Nb 2 O 5 have small or undetectable hysteresis, which becomes detectable and increases with increasing Nb 2 O 5 layer thickness. For the best device, energy conversion efficiency of up to 12%, short-circuit currents of 17 mA/cm 2 and fill factors of 74% were found. These parameters are comparable to the best performance of similar devices where the compact layer is TiO 2 . In addition, the use of Nb 2 O 5 improved the stability of the solar cells under illumination. These improvements are attributed to a better extraction of photogenerated electrons in the perovskite layer.

Hybrid perovskite crystals with organic and inorganic structural components are able to combine desirable properties from both classes of materials. Electronic interactions between the anionic inorganic framework and functional organic cations (such as chromophores or semiconductors) can give rise to unusual photophysical properties. Cyanine dyes are a well known class of cationic organic dyes with high extinction coefficients and tunable absorption maxima all over the visible and near-infrared spectrum. Here we present the synthesis and characterization of an original 1D hybrid perovskite composed of NIR-absorbing cyanine cations and polyanionic lead halide chains. This first demonstration of a cyanine-perovskite hybrid material is paving the way to a new class of compounds with great potential for applications in photonic devices.

A simple lamination process of the top electrode for perovskite solar cells is demonstrated. The laminate electrode consists of a transparent and conductive plastic/metal mesh substrate, coated with an adhesive mixture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, and sorbitol. The laminate electrode showed a high degree of transparency of 85%. Best cell performance was achieved for laminate electrodes prepared with a sorbitol concentration of ~30 wt% per milliliter PEDOT:PSS dispersion, and using a pre-annealing temperature of 120°C for 10 min before lamination. Thereby, perovskite solar cells with stabilized power conversion efficiencies of (7.6 ± 1.0)% were obtained which corresponds to 80% of the reference devices with reflective opaque gold electrodes.

Tinted and colour-neutral semitransparent organic photovoltaic elements are of interest for building-integrated applications in windows, on glass roofs or on facades. We demonstrate a semitransparent organic photovoltaic cell with a dry-laminated top electrode that achieves a uniform average visible transmittance of 51% and a power conversion efficiency of 3%. The photo-active material is based on a majority blend composed of a visibly absorbing donor polymer and a fullerene acceptor, to which a selective near-infrared absorbing cyanine dye is added as a minority component. Our results show that organic ternary blends are attractive for the fabrication of semitransparent solar cells in general, because a guest component with a complementary absorption can compensate for the inevitably reduced current generation capability of a high-performing binary blend when applied as a thin, semitransparent film.