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The electron-selective layer (ESL) is an indispensable component of perovskite solar cells (PSCs) and is responsible for the collection of photogenerated electrons. Preparing ESL at a low temperature is significant for future fabrication of flexible PSCs. In this work, solution-processed amorphous WO(x) thin film was prepared facilely at low temperature and used as ESL in PSCs. Results indicated that a large quantity of nanocaves were observed in the WO(x) thin film. In comparison with the conventional TiO2 ESL, the WO(x) ESL exhibited comparable light transmittance but higher electrical conductivity. Compared with the TiO2-based PSCs, PSCs that use WO(x) ESL exhibited comparable photoelectric conversion efficiency, larger short-circuit current density, but lower open-circuit voltage. Electrochemical characterization indicated that the unsatisfied open-circuit voltage and fill factor were caused by the inherent charge recombination. This study demonstrated that this material is an excellent candidate for ESL.

We report photovoltaic performances of all-solid state Sn/Pb halide-based perovskite solar cells. The cell has the following composition: F-doped SnO2 layered glass/compact titania layer/porous titania layer/CH3NH3SnxPb(1-x)I3/regioregular poly(3-hexylthiophene-2,5-diyl). Sn halide perovskite itself did not show photovoltaic properties. Photovoltaic properties were observed when PbI2 was added in SnI2. The best performance was obtained by using CH3NH3Sn0.5Pb0.5I3 perovskite. 4.18% efficiency with open circuit voltage 0.42 V, fill factor 0.50, and short circuit current 20.04 mA/cm(2) are reported. The edge of the incident photon to current efficiency curve reached 1060 nm, which was 260 nm red-shifted compared with that of CH3NH3PbI3 perovskite solar cells.

Mesoporous-graphitic-carbon-supported HfO2 (HfO2 -MGC) nanohybrids were synthesized by using a soft-template route. Characterization and a systematic investigation of the catalytic properties, stability, and catalytic mechanism were performed for HfO2 -MGC counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The new HfO2 -MGC as a CE in DSSCs showed a surprisingly high efficiency of 7.75 % for the triiodide/iodide redox couple and 3.69 % for the disulfide/thiolate redox couple, greater than the Pt electrode in the corresponding electrolyte system, which opens up a possibility for its practical application., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Low-cost quantum-dot sensitized solar cells (QDSSCs) were fabricated by using the earth-abundant element SnS quantum dot, novel TiC counter electrodes, and the organic disulfide/thiolate (T(2)/T(-)) redox couple, and reached an efficiency of 1.03 %. QDSSCs based on I(-)/I(3)(-), T(2)/T(-), and S(2-)/S(x)(2-) redox couples were assembled to study the role of the redox couples in the regeneration of sensitizers. Charge-extraction results reveal the reasons for the difference in J(SC) in three QDSSCs based on I(-)/I(3)(-), T(2)/T(-), and S(2-)/S(x)(2-) redox couples. The catalytic selectivity of TiC and Pt towards T(2)/T(-) and I(-)/I(3)(-) redox couples was investigated using Tafel polarization and electrochemical impedance analysis. These results indicated that Pt and TiC show a similar catalytic selectivity for I(-)/I(3)(-). However, TiC possesses better catalytic activity for T(2)/T(-) than for I(-)/I(3)(-). These results indicate the great potential of transition metal carbide materials and organic redox couples used in QDSSCs., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)