International audienc

Nanostructured photovoltaic devices were fabricated using a porous n-type TiO2 film, a thin layer of CdS acting as the absorber, and a transparent p-type CuSCN filling the pores. The cell showed an internal quantum efficiency of ∼100% and significant cell efficiency of 1.3% at 1 sun, as well as high photovoltage (0.85 V) and a filling factor of 0.65. Though the cell concept was already proposed by others, this cell clearly shows a significant performance and it demonstrates the potentiality of such cells made with very thin absorber layers (<10−20 nm) and largely structured porous films (roughness factor >100). Description of component characterization and explanation of identified issues are presented.

New metal complexes of the type [M(H3tcterpy)LY]+ (where M = Os(II) or Ru(II), L = substituted or unsubstituted bipyridine or pyridylquinoline, and Y = Cl-, I-, or SCN-) have been designed, synthesized, and characterized in view of their application for dye-sensitized solar cells (DSSCs). The Os dyes show a very broad absorption, and correspondingly, the DSSCs show an unprecedented spectral response in the NIR, with an onset at 1100 nm, reaching values of about 50% at 900 nm. The integrated photocurrent of some of such Os dyes is similar to that of the well-known [Ru(Htcterpy)(NCS)3](TBA) and superior to that of the [Ru(Hdcbpy)2(NCS)2](TBA)2 sensitizer. The Ru dyes show absorption and DSSC spectral response between those of the red and black dyes. Their advantage is their potential superior stability due to the reversible oxidative electrochemistry.

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Photovoltaic cells with the structure of nanocrystalline TiO2/Sb2S3/(LiSCN)CuSCN were prepared following the extremely thin absorber cell concept and characterized under different gas atmospheres. The cells showed an important light soaking effect in which the cell performance typically evolved from an initial lower efficiency into a higher one in contact with ambient air. Oxygen was shown to be involved with the effect. The best cell efficiency was 3.7% at ∼1 sun, with a photocurrent J sc normalized at 1 sun of 11.6 mA/cm2, an open-circuit voltage V oc of 0.56 V, and a filling factor, ff, of 0.58. The cells are shown to run more than 300 days, keeping the efficiency higher than 1.5% at ∼1 sun. The need for taking into account the influence of oxygen and humidity during photovoltaic measurement is emphasized for further investigation of this type of cell.