Active-layer evolution and efficiency improvement of (CH3NH3 3Bi2I9-based solar cell on TiO2-deposited ITO substrate

We systematically investigated the development of film morphology and crystallinity of methyl-ammonium bismuth (III) iodide (MA(3)Bi(2)I(9)) through onestep spin-coating on TiO2-deposited indium tin oxide (ITO)/glass. The precursor solution concentration and substrate structure have been demonstrated to be critically important in the active-layer evolution of the MA(3)Bi(2)I(9)-based solar cell. This work successfully improved the cell efficiency to 0.42% (average: 0.38%) with the mesoscopic architecture of ITO/compact-TiO2/mesoscopic-TiO2 (meso-TiO2)/MA(3)Bi(2)I(9)/2,2',7,7'-tetrakis(N,N-di-4-methoxyphenylamino)-9,9'spiro-bifluorene (spiro-MeOTAD)/MoO3/Ag under a precursor concentration of 0.45 M, which provided the probability of further improving the efficiency of the Bi3+-based lead-free organic-inorganic hybrid solar cells.