Facile electron injection and extraction are two key attributes desired in electron transporting layers to enhance the efficiency of planar perovskite solar cells. Herein it is demonstrated that the incorporation of alkali metal dopants in mesoporous TiO 2 can effectively modulate electronic conductivity and improve the charge extraction process by counterbalancing oxygen vacancies acting as nonradiative recombination centers. Moreover, sulfate bridges (SO 4 2− ) grafted on the surface of K-doped mesoporous titania provide a seamless integration of absorber and electron-transporting layers that accelerate overall transport kinetics. Potassium doping markedly influences the nucleation of the perovskite layer to produce highly dense films with facetted crystallites. Solar cells made from K:TiO 2 electrodes exhibit power conversion efficiencies up to 21.1% with small hysteresis despite all solution coating processes conducted under ambient air conditions (controlled humidity: 25-35%). The higher device efficiencies are attributed to intrinsically tuned electronic conductivity and chemical modification of grain boundaries enabling uniform coverage of perovskite films with large grain size.

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Articles you may be interested inThermal and plasma enhanced atomic layer deposition of TiO2: Comparison of spectroscopic and electric properties J.Rutile-structured TiO2 deposited by plasma enhanced atomic layer deposition using tetrakis(dimethylamino)titanium precursor on in-situ oxidized Ru electrode J. Vac. Sci. Technol. A 32, 01A120 (2014); 10.1116/1.4843515 Plasmonic Au nanoparticles on 8nm TiO2 nanotubes for enhanced photocatalytic water splitting J. Renewable Sustainable Energy 5, 053104 (2013); 10.1063/1.4821177 Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputteringThe authors report the effect of hydrogen plasma treatment on TiO 2 thin films grown by atomic layer deposition as an effective approach for modifying the photoanode materials in order to enhance their photoelectrochemical performance. Hydrogen plasma treated TiO 2 thin films showed an improved absorption in the visible spectrum probably due to surface reduction. XPS analysis confirmed the formation of Ti 3þ states upon plasma treatment. Hydrogen plasma treatment of TiO 2 films enhanced the measured photocurrent densities by a factor of 8 (1 mA/cm 2 at 0.8 V versus normal hydrogen electrode) when compared to untreated TiO 2 (0.12 mA/cm 2 ). The enhancement in photocurrent is attributed to the formation of localized electronic states in mid band-gap region, which facilitate efficient separation and transportation of photo excited charge carriers in the UV region of electromagnetic spectrum.

The authors, report here on the deposition of metallic copper thin films by plasma-assisted atomic layer deposition (ALD) with an air stable and volatile precursor À [Cu((Py)CHCOCF 3 ) 2 ] 2 (Py ¼ pyridine) À that stands out due to its facile synthesis and easy handling under ambient conditions. Copper thin films are obtained by decomposing [Cu((Py)CHCOCF 3 ) 2 ] 2 in hydrogen plasma in a concomitant deposition and recrystallization process. The thermal stability of the precursor prevents thermally induced decomposition, which allows precise control over thickness and film homogeneity. Electrical measurements of the as-deposited samples show clear interdependence of sheet resistance on the substrates surface roughness, thereby, films with higher roughness show higher resistance. Combined X-Ray photoelectron spectroscopy of Cu 2p peak and Cu LMM peak, as well as resistivity values of 58 V & À1 confirm the high quality of copper films without the need of further annealing steps under reducing atmosphere.