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

Vertically oriented highly crystalline 2D layered (BA) 2 (MA) n −1 Pb n I 3 n +1 (BA = CH 3 (CH 2 ) 3 NH 3 , MA = CH 3 NH 3 , n = 3, 4) perovskite thin‐films are fabricated with the aid of ammonium thiocyanate (NH 4 SCN) 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 ( H r = 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 Pb n I 3 n +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 Pb 3 I 10 perovskite ( n = 3) with the precursor composition of BAI:methylammonium iodide:PbI 2 :NH 4 SCN = 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 Pb 4 I 13 ( 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.