Natalia Yantara1 Annalisa Bruno1 Azhar Iqbal1 Nur Fadilah Jamaludin1 Cesare Soci1 Subodh Mhaisalkar1 Nripan Mathews1

1, Nanyang Technological University, Singapore, , Singapore

Ruddlesden Popper (RP) perovskites are of great interest in light emitting diodes (LED), due to the efficient energy transfer (funneling) from high bandgap (donor) domains to low bandgap (acceptor) domains which lead to enhanced photoluminescence (PL) intensity, long PL lifetime, and high efficiency LED. However, the influence of reduced effective emitter centers in the active emissive film as well as the implications of electrical injection into the larger bandgap donor material have not been addressed in the context of an active device. We critically assess and modulate the electrical and optical signatures of the energy cascading mechanisms in a model Ruddlesden Popper perovskite series ((C8H17NH3)2(CH(NH2)2)m-1PbmBr3m+1). Optimised devices demonstrated a current efficiency of 22.9 cd A-1 and 5% external quantum efficiency, more than 5 times higher than systems where funneling was absent. The signature of non-ideal funneling in RP perovskites is revealed by the appearance of donor electroluminescence from the device, followed by a reduction in the LED performance