Inkjet Printing Efficient Defined-Pixel Matrix Perovskite Light-Emitting Diodes with a Polar Polymer Modification Layer

Perovskite light-emitting diodes (PeLEDs) for full-color displays based on inkjet printing technology are increasingly attractive. For potential applications, fabricating high-quality perovskite films with defined-pixel sizes is crucially important. The key issue is how to control the contact properties between the perovskite ink and a hole transport layer (HTL). In this study, a novel strategy is proposed by using the poly[(9,9-bis(3 '-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (PFN-Br) polar polymer to modify the HTL surface, instead of conventional O-2 plasma method. The PFN-Br can enhance the surface energy of HTLs, including PVK, Poly-TPD, TFB, etc., and improve the wettability of perovskite inks on the HTL due to its polar quaternary ammonium groups. Besides, the PFN-Br acts as the easier nucleation to induce a tiny crystallization of perovskites. On the other hand, the diphenyl phosphate liver (DPA) is first used to mix in perovskite inks to optimize the perovskite film phase distribution and the elimination of uncoordinated Pb2+, resulting from interactions between PEA(+) and DPA, Pb2+ and DPA, respectively. As a result, a defined-pixel matrix green quasi-2D PeLED with the peak external quantum efficiency over 10% via inkjet printing technique is achieved, which is the most efficient matrix green PeLEDs fabricated by inkjet printing technique so far.