In our work on solid-state dye-sensitized solar cells (ssDSSC) we have recently [1] shown that copper phenanthroline complexes can act as an efficient hole transporting material. We prepared ssDSCs with the organic dye LEG4 and copper(I/II)-phenantroline as redox system and achieved power conversion efficiencies of more than 8%. For perovskite solar cells (PSC) our best performance is presently achieved with a mixed composition of iodide/bromide and methyl ammonium/formamidinium [1]. We will report on our work on optimizing the solar cell efficiency that at present shows a certified world record efficiency of 21.0%. With the use of an ALD deposited SnO2 compact underlayer we have constructed a planar perovskite solar cell with a hysteresis free efficiency of above 18% [2]. Based on this configuration we have in collaboration with the group of Prof. Bernd Rech, Helmholtz Zentrum Berlin, prepared a monolithic Perovskite/Silicon-Heterojunction tandem solar cell with an efficiency above 18% [3], pointing out a promising direction for further improvement of tandem cells using PSCs as one of the constituents. Another possibility for a tandem system has been investigated in collaboration with Prof. Segawa and co-workers in which a spectral split-cell, using a combination of a DSSC cell (with a wideband dye DX3) and a perovskite cell, demonstrated an efficiency of 21.5% [4].

[1] Bi et al., Science Advance, accepted

[2] Correa et al., Energy & Envir. Sci., DOI:10.1039/C5EE02608C

[3] Albrect et al., Energy & Envir. Sci., DOI: 10.1039/C5EE02965A

[4] Kinoshita et al., Nature Comm. DOI: 10.1038/ncomms9834