Lead-free perovskite solar cells using Sb and Bi-based A(3)B(2)X(9) and A(3)BX(6) crystals with normal and inverse cell structures

Research of CH(3)NH(3)PbI(3) perovskite solar cells had significant attention as the candidate of new future energy. Due to the toxicity, however, lead (Pb) free photon harvesting layer should be discovered to replace the present CH(3)NH(3)PbI(3) perovskite. In place of lead, we have tried antimony (Sb) and bismuth (Bi) with organic and metal monovalent cations (CH(3)NH(3) (+), Ag(+) and Cu(+)). Therefore, in this work, lead-free photo-absorber layers of (CH(3)NH(3))(3)Bi(2)I(9), (CH(3)NH(3))(3)Sb(2)I(9), (CH(3)NH(3))(3)SbBiI(9), Ag(3)BiI(6), Ag(3)BiI(3)(SCN)(3) and Cu(3)BiI(6) were processed by solution deposition way to be solar cells. About the structure of solar cells, we have compared the normal (n-i-p: TiO(2)-perovskite-spiro OMeTAD) and inverted (p-i-n: NiO-perovskite-PCBM) structures. The normal (n-i-p)-structured solar cells performed better conversion efficiencies, basically. But, these environmental friendly photon absorber layers showed the uneven surface morphology with a particular grow pattern depend on the substrate (TiO(2) or NiO). We have considered that the unevenness of surface morphology can deteriorate the photovoltaic performance and can hinder future prospect of these lead-free photon harvesting layers. However, we found new interesting finding about the progress of devices by the interface of NiO/Sb(3+) and TiO(2)/Cu(3)BiI(6), which should be addressed in the future study.