Interlayer Cross‐Linked 2D Perovskite Solar Cell with Uniform Phase Distribution and Increased Exciton Coupling

A nonuniform vertical phase distribution and thick insulating barrier can decrease the energy transfer between slices in layered perovskite solar cells (PSCs). Herein, an interlayer cross‐linked Dion–Jacobson (DJ)‐type 2D PSC with 1,4‐butanediamine (BDA) as a short‐chain insulating spacer [formula: (BDA)MA n −1 Pb n I 3 n + 1 ] is reported and demonstrates the vertical phase becoming uniform with enhanced exciton coupling, leading to reduced nonradiative recombination. For n = 1 pure phase perovskite, an exciton binding energy of the DJ phase (BDA)PbI 4 is ≈142 meV, much smaller than ≈435 meV of Ruddlesden–Popper (RP) phase (BA) 2 PbI 4 ( n = 1) perovskite, indicative of exciton‐coupling‐induced efficient energy transfer. Therefore, the high energy emission peaks for the (BDA)MA 3 Pb 4 I 13 film are not observed even in liquid nitrogen temperature (78 K), which can be distinguished from that of the (BA) 2 MA 3 Pb 4 I 13 film. Energy transfer between 2D slices of (BDA)MA 3 Pb 4 I 13 is 100 times faster than that of (BA) 2 MA 3 Pb 4 I 13 . The uniform vertical distribution and exciton coupling mitigate nonradiative energy loss and significantly improve V oc in inverted structures (PEDOT:PSS/(BDA)MA 3 Pb 4 I 13 /PCBM/bathocuproine/Ag) to ≈1.15 V and the control n ‐butylammonium‐based device demonstrates only a V oc = ≈1 V. It is believed that the results would provide a deep understanding of exciton coupling in hybrid multicomponent quantum wells.