Dielectric confinement effect on excitons inPbI4-based layered semiconductors

Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells

“…Subsequently, a slower decay of the PB of n=2 QWs also matches well with a relative slower formation of the large-n QWs PB. This relatively slower exciton localisation time is fitted to be ~50 ps.The rapid energy transfer process in the perovskite MQWs can essentially avoid the exciton quenching effect presented in previously reported 2D perovskites 6,7 . Figure 1h shows the light-intensity-dependent PLQE of the NFPI7 film under a 445 nm cw laser excitation.…”

“…The 2D L2MX4 perovskites generally have good film-formation properties 13 . Nevertheless, the PLQEs of the 2D perovskites are rather low at room temperature, owing to fast exciton quenching rates 6,7 . LEDs based on the 2D perovskites have been attempted, while the devices are either very low in efficiency or only operational at cryogenic temperatures [16][17][18] .…”

“…However, the efficiency of their electroluminescence is limited by nonradiative recombination associated with defects and leakage current due to incomplete surface coverage [6][7][8][9] . Here we demonstrate a solution-processed perovskite light-emitting diode (LED) based on self-organised multiple quantum wells (MQWs) with excellent film morphology.…”

“…Because of the quantum confinement effects, the absorption and emission features of the layered perovskites depend on the value of n 6,15 . Previous studies on PbI4-based perovskites showed that the absorption peaks at ~2.4, ~2.2, ~2.0 and ~1.9 eV correspond to excitonic absorption of QWs with n=1, 2, 3 and 4 respectively 6,20,21 . Our results confirm that the (NMA)2PbI4 perovskite film, i.e.…”

“…Here n is the number of semiconducting MX4 monolayer sheets within the two organic insulating layers (cation L), with n=∞ corresponding to the structure of a 3D perovskite SMX3. With smaller numbers of MX4 layers, quantum confinement effects, such as an increase in bandgap and exciton energy, become important 6,15 . In consequence, the layered perovskites naturally form quantum-well structures.…”