Stable decaphenylcyclopentasilane hole transport layers for double-stacked perovskite photovoltaic devices fabricated under ambient atmosphere

Stable decaphenylcyclopentasilane (DPPS) hole transport layers were developed for guanidinium-, formamidinium-, or ethylammonium-added double-stacked CH 3 NH 3 PbI 3 perovskite photovoltaic devices without using 2,2′,7,7′-tetrakis ( N,N -di- p -methoxyphenylamino)-9,9′-spirobifluorene, which is a typical hole transport layer. Stacking two types of perovskite compounds inserted within the DPPS layer enabled the fabrication of stable perovskite solar cells under ambient atmosphere at 190 ​°C, which reduced the trap density and improved the photovoltaic properties of the devices. As expected, the DPPS-inserted layers functioned as a stable hole transport layer for perovskite solar cells. (a) Schematic illustration of the process used to fabricate the DPPS-inserted double stacked perovskite solar cells. (b) Changes in the conversion efficiencies and (c) energy level diagram of the present cells. • Stable DPPS hole transport layers were developed for perovskite solar cells. • Stacking two types of perovskite compounds was effective for the efficiencies. • DPPS suppressed trap densities and improved the photovoltaic properties. • DPPS could be expected as one of the alternative materials to spiro-OMeTAD.