LAUSR

Abstract In a nutshell, this study outlines the efficacy of mixed dimensional (2D/3D) hybrid perovskites by developing a new class of triple-cation quasi-2D perovskites having (S 0.97 S′ 0.03 ) 2 [Cs 0.05 (FA 0.97 MA 0.03 ) 0.95 ] n-1 Pb n (I 0.07 Br 0.03 ) 3n+1 general composition, in which a mixture of ý5-ammonium valeric acid ýiodideý‏ (S) and ‏tetra-n-octylammonium ýbromide (S′) was employed ýas a spacer.ý The effect of the 2D and 3D structures molar ratios (i.e., C=2D/2D+3D) in the range of 0-100 % on photovoltaic performance of the deposited photoanodes was systemically studied. Drawing a comparison between such compounds and an analogous triple-cation 3D counterpart (i.e., Cs 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I 0.83 Br 0.17 ) 3 ) as a reference (i.e., C=0) showed that the C=10 film containing 10 % 2D and 90 % 3D perovskites had optimal properties for solar cell applications. The pronounced (0 k 0) peak series at low angles and the blue shift of the 3D perovskites peaks observed in X-ray diffraction set forth that quasi-2D perovskites were formed in the layers. The C=10 film having the bandgap of around 1.62 eV exhibited the optimal photon ýabsorption, light harvesting, and crystallinity compared to all the deposited layers, ensuring ýadequate photocurrent. CuInS 2 nanoparticles were employed as a novel hole-transporting material to assemble solar cells. The C=10 cell also indicated the highest power conversion efficiency (i.e., 12.33 %), recombination resistance (i.e., 1650.23 Ω), and electron lifetime (20.73 μs) as well as the lowest series resistance of 10.23 Ω amongst all the 2D/3D films, demonstrated by electrochemical impedance spectroscopy (EIS). Although the efficiency of this cell was not yet sufficient to compete with that of the C=0 (i.e., 12.87 %), it could retain 80 % of its own performance over 2500 h in ambient conditions without encapsulation, endowing more stability than its 3D counterpart which sustained 64 % of the initial efficiency. Therefore, developing triple-cation 2D/3D perovskites is a facile, straightforward strategy for fabricating stable, efficient solar cells.