Arora, NehaDar, M. IbrahimHinderhofer, AlexanderPellet, NormanSchreiber, FrankZakeeruddin, Shaik MohammedGraetzel, Michael2017-12-042017-12-042017-12-04201710.1126/science.aam5655https://infoscience.epfl.ch/handle/20.500.14299/142570WOS:000414847100040Perovskite solar cells (PSCs) with efficiencies greater than 20% have been realized only with expensive organic hole-transporting materials. We demonstrate PSCs that achieve stabilized efficiencies exceeding 20% with copper(I) thiocyanate (CuSCN) as the hole extraction layer. A fast solvent removal method enabled the creation of compact, highly conformal CuSCN layers that facilitate rapid carrier extraction and collection. The PSCs showed high thermal stability under long-term heating, although their operational stability was poor. This instability originated from potential-induced degradation of the CuSCN/Au contact. The addition of a conductive reduced graphene oxide spacer layer between CuSCN and gold allowed PSCs to retain >95% of their initial efficiency after aging at a maximum power point for 1000 hours under full solar intensity at 60 degrees C. Under both continuous full-sun illumination and thermal stress, CuSCN-based devices surpassed the stability of spiro-OMeTAD-based PSCs.text::journal::journal article::research article