(34d) Ultrafast Carrier Dynamics in Bimetallic Nanostructures-Enhanced Methylammonium Lead Bromide Perovskites | AIChE

(34d) Ultrafast Carrier Dynamics in Bimetallic Nanostructures-Enhanced Methylammonium Lead Bromide Perovskites

Authors 

Bardhan, R. - Presenter, Vanderbilt University
An unprecedented rise in efficiency has been observed in methylammonium lead trihalide (MAPbX3, X=I, Cl, Br) perovskite solar cells (PSCs) reaching >20% recently. While MAPbI3 perovskites have been the primary focus in PSCs, the poor stability and rapid degradation in humidity has remained a major obstacle in MAPbI3. MAPbBr3 is a promising alternative to MAPbI3 with a large 2.2 eV bandgap which gives rise to a high open circuit voltage, long exciton diffusion length (>1.2 μm) enabling good charge transport in devices, and higher moisture stability due to its stable cubic phase and low ionic mobility relative to the pseudocubic MAPbI3. However, a relatively large exciton binding energy (76 meV) and poor light absorption beyond its band edge at 550 nm has limited the efficiencies for MAPbBr3 solar cells. In this work, we examine the impact of hybrid bimetallic Au/Ag core/shell plasmonic nanostructures on the carrier dynamics of methylammonium lead tribromide (MAPbBr3) mesoporous PSCs.1 Plasmon-enhancedPSCs incorporated with Au/Ag nanostructures demonstrated improved light harvesting and increased power conversion efficiency by 26% relative to reference devices. Two complementary spectral techniques, transient absorption spectroscopy (TAS) and time-resolved photoluminescence (trPL), were employed to gain a mechanistic understanding of plasmonic enhancement processes. TAS revealed a decrease in photobleach formation time which suggests that the nanostructures improve hot carrier thermalization to an equilibrium distribution, relieving hot phonon bottleneck in MAPbBr3 perovskites. TAS also showed a decrease in carrier decay lifetimes indicating nanostructures enhance photoinduced carrier generation and promote efficient electron injection into TiO2 prior to bulk recombination. Further, nanostructure-incorporated perovskite films demonstrated quenching in steady-state PL and decreases in trPL carrier lifetimes, providing further evidence of improved carrier injection in plasmon-enhanced mesoporous PSCs.

1. H. F. Zarick, A. Boulesbaa, A. A. Puretzky, E. M. Talbert, Z. Debra, N. Soetan, D. B. Geohegan, and R. Bardhan*, Nanoscale, 2017, 9, 1475-1483