Vertically Oriented 2D Layered Perovskite Solar Cells with Enhanced Efficiency and Good Stability

Vertically oriented highly crystalline 2D layered (BA)(2)(MA)(n-1)PbnI3n+1 (BA = CH3(CH2)(3)NH3, MA = CH3NH3, n = 3, 4) perovskite thin-films are fabricated with the aid of ammonium thiocyanate (NH4SCN) additive through one-step spin-coating process. The humidity-stability of the film is certified by the almost unchanged X-ray diffraction patterns after exposed to humid atmosphere (Hr = 55 +/- 5%) for 40 d. The photovoltaic devices with the structure of indium tin oxide(ITO)/poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate)/(BA)(2)(MA)(n-1)PbnI3n+1(n = 3,4)/[6,6]-phenyl-C-61-butyric acid methyl ester/Bathocuproine/Ag are fabricated. The devices based on (BA)(2)(MA)(2)Pb3I10 perovskite (n = 3) with the precursor composition of BAI:methylammonium iodide: PbI2:NH4SCN = 2:2:3:1 (by molar ratio) show an averaged power conversion efficiency (PCE) of 6.82%. In the case of (BA)(2)(MA)(3)Pb4I13 (n = 4), a higher PCE of 8.79% is achieved. Both of the unsealed devices perform unique stability with almost unchanged PCE during the period of storage in purified N-2 glove box. This work provides a simple and effective method to enhance the efficiency of the 2D perovskite solar cell.