Reduced Surface Trap States of PbS Quantum Dots by Acetonitrile Treatment for Efficient SnO2-Based PbS Quantum Dot Solar Cells.

The solution-phase ligand-exchange strategy offers a simple pathway to prepare PbS quantum dots (QDs) and their corresponding solar cells. However, the production of high-quality PbS QDs with reduced surface trap state density for efficient PbS QD solar cells (QDSCs) still faces challenges. As the hydroxyl group (-OH) has been demonstrated to be the primary source of the surface trap states on PbS QDs in the general oleic acid method, here, we present an effective and facile strategy for reducing the surface -OH content of PbS QDs by using acetonitrile (ACN) as precipitant to wash the surface of QDs, which significantly decreases the trap state density and enables the preparation of superior PbS QDs. The resulting solar cell with an ITO/SnO2/n-PbS/p-PbS/Au structure obtained an improved photoelectric conversion efficiency (PCE) from 8.53 to 10.49% with an enhanced air storage stability, realizing a high PCE for SnO2-based PbS QDSCs.

Two-dimensional triphenylene cored hole-transporting materials for efficient perovskite solar cells.

Two organic hole-transporting materials comprising a two-dimensional triphenylene core and methoxyl-arylamine terminal units are developed and applied in perovskite solar cells. Enhanced photovoltaic and stability performance are obtained using TPH-T compared with those of spiro-OMeTAD.

Gradient-band-gap strategy for efficient solid-state PbS quantum-dot sensitized solar cells.

To improve charge separation and enhance open-circuit voltage (Voc) in solid-state quantum-dot sensitized solar cells (QDSCs), gradient-band-gap PbS quantum-dots were first and easily constructed by two-step spin-coating the Pb(NO3)2 solution and the mixed solution of Na2S and 1,2-ethanedithiol via successive ionic layer absorption and reaction (SILAR). The fabricated solid-state gradient-band-gap PbS QDSCs exhibited a Voc of 0.70 V, a short-circuit photocurrent density (Jsc) of 9.65 mA·cm-2, a fill factor (FF) of 0.60, and a photoelectric conversion efficiency (PCE) of 4.08%, while the inverse gradient-band-gap PbS QDSCs showed a Voc of 0.59 V, a Jsc of 5.86 mA·cm-2, an FF of 0.49 and a PCE of 1.69%. By optimization, the best solid-state gradient-band-gap PbS QDSCs achieved a Voc of 0.65 V and a PCE of 6.29% under 1 sun, and a Voc of 0.60 V and a PCE of 7.21% under 0.5 sun. The Voc of 0.65 V was relatively high, and the PCE of 6.29% was the highest value among solid-state QDSCs constructed using SILAR.

Br-Doping CH3NH3PbI3-xBrx Thin Films for Efficient TiO2 Nanorod Array Perovskite Solar Cells.

CH3NH3PbI3-xBrx thin films with different Br contents were successfully prepared on TiO2 nanorod array using 1.7 M PbI2 · DMSO complex solution and 0.465 M CH3NH3x(x = Br, I) precursors with different CH3NH3Br contents (molar ratios) by sequential deposition method. The influence of CH3NH3Br contents on the chemical composition, crystallinity, optical absorption and surface morphology of the CH3NH3PbI3-xBrx thin films was systematically investigated, and the photovoltaic performance of the corresponding TiO2 nanorod array perovskite solar cells was evaluated. The results revealed that the CH3NH3PbI3-xBrx solar cells using CH3NH3x precursors with 5% CH3NH3Br exhibited the best photoelectric conversion efficiency (PCE) of 16.47%, along with an open-circuit voltage (Voc) of 1.02 V, short-circuit photocurrent density (Jsc) of 20.99 mA · cm-2 and fill factor (FF) of 0.77, and the average PCE of 16.06 ± 0.52%, along with Voc of 1.02 ± 0.01 V, Jsc of 20.41 ± 0.58 mA · cm-2 and FF of 0.77 ± 0.01 under illumination of simulated AM 1.5 sunlight (100 mA cm-2).

SnS Thin Film Prepared by Pyrolytic Synthesis as an Efficient Counter Electrode in Quantum Dot Sensitized Solar Cells.

The SnS thin films were successfully prepared by pyrolysis procedure for the counter electrodes in quantum dot sensitized solar cells (QDSCs) using the methanol solution containing stannous chloride dihydrate (0.40 mol x L(-1)) and thiourea (0.40 mol x L(-1)) as precursor solution at 300 degrees C in the air atmosphere. The electrochemical catalytic activity of the SnS thin films prepared by pyrolytic synthesis for the redox couple of S(2-)/S(2-) was investigated by electrochemical impedance spectroscopy. The result revealed that the charge transfer resistance of the as-prepared SnS thin film with the dipping-heating cycles of 5 was 106.4 Ω and the corresponded QDSCs gave a short circuit photocurrent density of 8.69 mA x cm(-2), open circuit voltage of 0.42 V, and fill factor of 0.43, yielding the photoelectric conversion efficiency of 1.57%, under the illumination of simulated AM 1.5 sunlight (100 mWx cm(-2)).

A two-layer structured PbI2 thin film for efficient planar perovskite solar cells.

In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm(-2) and a fill factor of 0.67.

Hydrothermal fabrication and characterization of polycrystalline linneite (Co(3)S(4)) nanotubes based on the Kirkendall effect.

In this study, polycrystalline linneite (Co(3)S(4)) nanotubes constructed with nanoparticles have been firstly fabricated using 1D Co(CO(3))(0.35)Cl(0.20)(OH)(1.10) nanowires as the sacrificial templates under hydrothermal conditions. The samples are characterized by means of XRD and TEM. The formation mechanism of the Co(3)S(4) nanotubes can be explained by the nanoscale Kirkendall effect, which results from the difference in diffusion rates between cobalt source and hydrogen sulfide. This simple synthetic route is expected to prepare other nanomaterials with the tubular structures.