Effects of FK209-doping and layer-stackings for DPPS hole transport layers in perovskite solar cells

Doping and stacking effects for decaphenylcyclopentasilane (DPPS) hole transport layers in perovskite photovoltaic devices were investigated. Tris(2-(1 H -pyrazol-1-yl)-4- tert -butylpyridine)cobalt(III) tri[bis(trifluoromethane)sulfonimide] (FK209) was added to DPPS as dopant, and the conversion efficiency of the DPPS stacked devices doped with FK209 increased over 12 % after 43 days, which is almost same as that of spiro-OMeTAD, a conventional hole transport material. A three-layered perovskite/DPPS stacking structure also improved the conversion efficiencies of the devices. The first-principles calculation indicated the hole transport mechanism of DPPS. The calculated adsorption energy of DPPS with cations in the perovskite was found to be high, which would contribute to suppressing the desorption of CH 3 NH 3 . The present results indicated that equivalent efficiencies can be obtained using only chemically stable materials such as DPPS and FK209, without using unstable materials such as spiro-OMeTAD and Li-TFSI.