Lewis Base Passivation of Quasi-2D Ruddlesden–Popper Perovskite for Order of Magnitude Photoluminescence Enhancement and Improved Stability

Abstract

Quasi-two-dimensional (2D) Ruddlesden–Popper (RP) perovskites are currently considered as the material of choice for the next-generation light-emitting diodes (LEDs) due to their superior optoelectronic properties. Despite their spectacular external quantum efficiency, the excessive surface defect states generated due to the reduced crystal size and phase impurity limit their radiative recombination efficiency. In the present work, we have shown the order of magnitude enhancement of radiative emission in butylamine (BA)-based quasi-2D perovskite (BA)2(MA) n−1Pb n Br3n+1 after passivating with two different Lewis basesa small organic molecule triphenylphosphine oxide (TPPO) and an insulating polymer polymethyl methacrylate (PMMA). The reduction in crystal grain size was observed after passivation, attributed to the complexation of the passivating molecules (PM) on the surface and nanocrystal pinning (A-NCP) phenomena. Both the steady-state and time-resolved photoluminescence study confirmed significant enhancement in fluorescence intensity and improved average lifetime (τavg. = 19.4 ns) after surface passivation. The interaction mechanism between the layered perovskite and PMs was probed with FTIR spectroscopy, XPS, and KPFM study. All these studies confirmed that the CO group in PMMA and PO group in TPPO deactivate the acceptor-type defects (uncoordinated Pb2+ and Br vacancies) in these RP perovskites. Furthermore, the stability of the passivated film enhanced significantly, as confirmed by contact angle measurement. Our study establishes that uncoordinated Pb2+ passivation by a Lewis base provides a viable strategy for photoluminescence (PL) lifetime, intensity, and stability enhancement in quasi-2D perovskite films.

Conductive Phosphine Oxide Passivator Enables Efficient Perovskite Light-Emitting Diodes

“…The as-prepared perovskite films exhibited remarkable robustness against oxygen, moisture, and heat, and the corresponding Pero-LEDs showed a peak EQE of 14% and an operational half-lifetime (T 50 ) of 3.5 h at 4000 cd/m 2 . However, most phosphine oxide molecules used for defect passivation are electrically insulating (Table S1), which is adverse to charge injection and may limit the corresponding device performance. − In this way, it is highly demanded to develop a bifunctional molecule that can perform well in both defect passivation and charge injection. ,, …”

Stable Single‐Mode Lasing from a Hybrid Perovskite–Polymer Fiber

“…This is attributed to the interaction between the C-O-C bond and Lewis's acid Pb 2+ in the PMMA matrix. [16][17][18] Figure 2d fits the decay time of the samples by a single-exponential curve. It is calculated that the corresponding decay time is about 83.6 ns.…”

Light‐Emitting Perovskite Solar Cells: A Tale of Two States

“…[43][44][45] Moreover, it is possible to modulate the phase distribution in quasi-2D perovskites to tune the competition between carrier recombination and collection rates in the same system as different phase components have different bandgaps and simultaneously different exciton binding energies. [46] Second, better-quality quasi-2D perovskite films with less defect states and controlled charge mobility can be synthesized, which is critical for increased photovoltaic and LED efficiency. Third, additive engineering can easily produce better-quality quasi-2D perovskite films.…”