Study and Development of Photovoltaic Structures Based on Quantum Dot Solids of PbS with Various Ligands

The photoconductivity of condensates of lead-sulfide quantum dots (QDs)—QD solids—with various organic ligands is studied. It is demonstrated that the QD solid photoconductivity increases exponentially with a reduction in length of ligand molecules and does not depend on their chemical structures, since it is governed by hopping transport of charge carriers. In contrast, the photocurrent in photovoltaic ITO/PEDOT: PSS/PbS/ZnO/Al elements depends on the ligand structure, since this structure sets the positions of QD energy levels and thus affects the efficiency of charge carrier transfer to electrodes. The difference between mechanisms of generation of photoconductivity and photovoltaic currents is discussed.     

Sensitization of the photoelectric effect in carbazole- and indolocarbazole-containing poly(phenylquinoline)s by benzothiadiazole acceptor molecules

The efficient sensitization of the photoelectric effect in mixed compositions of poly(phenylquinoline)s (PPQ) with 2,1,3-benzothiadiazole (BTDZ) molecules is established. The introduction of 10 wt % BTDZ results in extension of the spectral sensitivity range of PPQ and an increase in the photosensitivity and photocurrent by factors of 4.5 and more than 6, respectively. It is shown that the effect is caused by complex formation between PPQ donor fragments and BTDZ acceptor molecules; the strongest, in comparison with the increase in photosensitivity, is probably caused by the transport of free photogenerated carriers (electrons) over sensitizer molecules introduced into the polymer.     

The influence of the atmosphere on hole transport in poly(diphenylenephthalide) films

The influence of ambient air on hole mobility in thin polydiphenylenephthalide films has been studied. The current-voltage characteristics of samples of diode configuration with unipolar conductivity have been measured in air and inert atmosphere with controllable oxygen and water. It has been shown that the hole mobility measured in the inert atmosphere exceeds the mobility measured in air by no less than 1.5 times.     

The Effect of a Nanosize TiO<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript> Layer on the Performance of an Organic Solar Cell

This work studies the role of a cathodic TiO_x buffer layer in operation of a photovoltaic organic solar cell (OSC) based on a photoactive layer with a bulk heterojunction. Using a liquid solution to obtain a TiO_x layer is of current interest for simplification of process technologies of successive formation of OSC layers. It is found that the optimum thickness of the TiO_x layer is 10 nm; at this thickness, the efficiency of the OSC reaches the value of 4.36%. The effect of air oxygen on the OSC samples is studied and it is found that samples with a TiO_x buffer layer undergo degradation to a lesser extent as compared to the samples with no such layer. The effect of oxygen on operation of the photovoltaic device is discussed.     

The photovoltaic effect and charge carrier mobility in layered compositions of bithiophene or related rotaxane copolymer with C<Subscript>70</Subscript> fullerene derivative

Organic photovoltaic cells with a bulk heterojunction have been manufactured in which the photoactive layer consists of a mixture of bithiophene copolymer or related rotaxane with a fullerene derivative (PC₇₀BM). The mobility of charge carriers in photoactive layers has been determined, the current–voltage characteristics of photovoltaic cells have been measured, and the energy level diagram of cell components has been constructed. It is established that the polyrotaxane component (macrocycle) insulates a part of thiophene fragments of the macromolecule, thus hindering the transport of carriers and leading to large energy losses for exciton dissociation, which results in a decreasing photovoltaic effect.     

Photophysical properties of indolo[3,2-b]carbazoles as a promising class of optoelectronic materials

The photophysical properties of new synthesized indolocarbazoles, i.e., indolo[3,2-b]carbazole and its derivatives, have been comparatively analyzed. It is shown that their photosensitivity (total photosensitivity to (5–8) × 10⁻² (lx s)⁻¹, spectral photosensitivity ∼10⁵ cm² J⁻¹, and free carrier photogeneration quantum yield of 0.1) and transport (effective mobility in 5,11-dioctyl indolo[3,2-b]carbazole is more than 10⁻⁵ cm²/(V s)) parameters significantly exceed those of pentacene, which, among molecular media (organic crystals), exhibits the highest carrier photogeneration quantum yields. The high photoluminescence intensity of synthesized indolo[3,2-b]carbazole derivatives shows promise for their applicability in electroluminescent devices.     

Photophysical and electrical properties of polyphenylquinolines containing carbazole or indolo[3,2-b]carbazole fragments as new optoelectronic materials

Photophysical and electrical properties of new synthesized 2,6-polyphenylquinolines (PPQs) containing an oxygen or phenylamine bridging group between quinoline cycles and, as an arylene radical, alkylated derivatives of carbazole or indolo[3,2-b]carbazole are studied. It is shown that the photosensitivity for new PPQs is 10⁴–10⁵ cm²/J and the photogeneration quantum yield of free carriers is as high as 0.15. Photophysical parameters increase with the phenylamine bridging group in place of the oxygen one and when using indolocarbazole instead of carbazole. It is found that a film of polyphenylquinoline containing an oxygen bridging group and an alkylcarbazole fragment in the polymer repeat unit exhibits “white” luminescence. Both electron and hole transport with a mobility of ∼10⁻⁶ cm²/(V s) are detected in films of all studied polymers. The conductivity value and type can be controlled by varying the chemical structure of the (oxygen or phenylamine) bridging group between PPQ cycles and by choosing carbazole or indolo[3,2-b]carbazole derivatives as an arylene radical.     

Features of the Temperature Dependences of the Photoconductivity of Organometallic CH3NH3PbI3 Perovskite Films

Semiconductors - The effect of temperature on the photoconductivity and its spectral dependence for thin films of organometallic CH3NH3PbI3 perovskite is studied. The measurements performed at...     

Ink-Jet Printing of Polyaniline Layers for Perovskite Solar Cells

Technical Physics Letters - Polyaniline-based water-soluble ink has been developed to form hole-transport layers for perovskite solar cells by the ink-jet printing method. A study of the optical...     

Bistable electronic switching in poly(arylenephthalides)

Experimental and theoretical data show that the phenomenon of bistable switching in thin films of poly(arylenephthalides) (PAPs), which was reported previously, has an electronic nature and is related to the unique properties of PAP molecules. This phenomenon has been studied in metal-PAP-metal and ITO-PAP-ITO structures (ITO = indium tin oxide) with various thicknesses of the polymer film. First results are reported that demonstrate the principal possibility of using thin PAP films as a basis for resistive nonvolatile electronic memory cells. These data show that the bistable switching is related primarily to the electronic properties of the polymer film and is not influenced by the oxidation of electrodes and/or the growth of metal filaments from the electrodes.