Incorporation of Cl into sequentially deposited lead halide perovskite films for highly efficient mesoporous solar cells.

Organic-inorganic lead halide perovskites have been widely used as absorbers on mesoporous TiO2 films as well as thin films in planar heterojunction solar cells, yielding very high photovoltaic conversion efficiencies. Both the addition of chloride and sequential deposition methods were successfully employed to enhance the photovoltaic performance. Here, both approaches are combined in a sequential method by spincoating PbCl2 + PbI2 on a mesoporous TiO2 film followed by the perovskite transformation. The role of Cl in determining the optical, electrical, structural and morphological properties is correlated with the photovoltaic performance. The highest photovoltaic efficiency of 14.15% with the V(oc), FF and J(sc) being 1.09 V, 0.65 and 19.91 mA cm(-2) respectively was achieved with 10 mol% of PbCl2 addition due to an increase of the film conductivity induced by a better perovskite morphology. This is linked to an improvement of the hysteresis and reproducibility of the solar cells.

Lead-free halide perovskite solar cells with high photocurrents realized through vacancy modulation.

Lead free perovskite solar cells based on a CsSnI3 light absorber with a spectral response from 950 nm is demonstrated. The high photocurrents noted in the system are a consequence of SnF2 addition which reduces defect concentrations and hence the background charge carrier density.

Cobalt dopant with deep redox potential for organometal halide hybrid solar cells.

In this work, we report a new cobalt(III) complex, tris[2-(1H-pyrazol-1-yl)pyrimidine]cobalt(III) tris[bis(trifluoromethylsulfonyl)imide] (MY11), with deep redox potential (1.27 V vs NHE) as dopant for 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD). This dopant possesses, to the best of our knowledge, the deepest redox potential among all cobalt-based dopants used in solar cell applications, allowing it to dope a wide range of hole-conductors. We demonstrate the tuning of redox potential of the Co dopant by incorporating pyrimidine moiety in the ligand. We characterize the optical and electrochemical properties of the newly synthesized dopant and show impressive spiro-to-spiro(+) conversion. Lastly, we fabricate high efficiency perovskite-based solar cells using MY11 as dopant for molecular hole-conductor, spiro-OMeTAD, to reveal the impact of this dopant in photovoltaic performance. An overall power conversion efficiency of 12% is achieved using MY11 as p-type dopant to spiro-OMeTAD.

High efficiency electrospun TiO2 nanofiber based hybrid organic-inorganic perovskite solar cell.

The good electrical and morphological characteristics of TiO2 nanofibers and the high extinction coefficient of CH3NH3PbI3 perovskite are combined to obtain a solar cell with a power conversion efficiency of 9.8%. The increase of the film thickness dramatically diminishes the performance due to the reduction in porosity of the TiO2 nanofiber framework. The optimum device (∼413 nm film thickness) is compared to a planar device, where the latter produces higher V(oc) but lower J(sc), and consequently lower efficiency at all measured light intensities.

Flexible, low-temperature, solution processed ZnO-based perovskite solid state solar cells.

A ZnO compact layer formed by electrodeposition and ZnO nanorods grown by chemical bath deposition (CBD) allow the processing of low-temperature, solution based and flexible solid state perovskite CH3NH3PbI3 solar cells. Conversion efficiencies of 8.90% were achieved on rigid substrates while the flexible ones yielded 2.62%.