Understanding the Role of Lithium Doping in Reducing Nonradiative Loss in Lead Halide Perovskites

Abstract

Adding alkali metal into lead halide perovskites has recently been demonstrated as an effective strategy for reducing nonradiative loss. However, the suggested role of the alkali metal is usually limited to surface passivation, and the semiconductor doping effect is rarely discussed. Here, the mechanism of lithium doping in the photocarrier recombination in solution‐processed methylammonium lead halide films is investigated by photoluminescence and photoelectron spectroscopies. It is demonstrated that lithium doping weakens the electron–phonon coupling and acts as donor in perovskites, which provide solid evidence that lithium enters the lattice rather than just in the surface region. The n‐type doping creates free electrons to fill the trap states in both the bulk and surface regions, leading to suppressed trapping of photocarriers and reduces nonradiative recombination.

Efficient and Hole‐Transporting‐Layer‐Free CsPbI2Br Planar Heterojunction Perovskite Solar Cells through Rubidium Passivation

“…Typically, A 1 and A 2 are the relative amplitudes, B is offset value, τ 1 represents the information for the interface recombination process, and τ 2 reflects the information for the bulk recombination process . The average lifetime τ avg has also been calculated to determine the whole recombination process, as given by Equation : …”

Extending Carrier Lifetimes in Lead Halide Perovskites with Alkali Metals by Passivating and Eliminating Halide Interstitial Defects

“…Fang et al. have observed that lithium can enter the lattice of MAPbI 3 and induce n‐type doping, creating free electrons to fill the trap states such as interstitial iodine, and suppressing nonradiative recombination . Son et al.…”

“…[22] Fang et al have observed that lithium can enter the lattice of MAPbI 3 and induce n-type doping, creating free electrons to fill the trap states such as interstitial iodine,and suppressing nonradiative recombination. [23] Son et al have investigated the role of potassium in passivating defects,reporting that potassium can be easily mixed into FA 0.85 MA 0.1 Cs 0.05 PbI 2.7 Br 0.3 and impede formation of interstitial iodine and other iodine-related Frenkel defects. [24] Thei ntroduction of potassium removes the current-voltage hysteresis,a nd reduces lowfrequency capacitance and trap density.A bdi-Jalebi et al have successfully controlled the nonradiative losses and photoinduced ion migration in perovskite films and interfaces by decorating surfaces and grain boundaries with potassium halide layers.…”

Bright and Effectual Perovskite Light-Emitting Electrochemical Cells Leveraging Ionic Additives

“…This PL trend with lithium doping can be understood from reduced trapping. 20 In the absence of lithium dopants, unfilled trap states are present, potentially due to grain boundaries, vacancies, and other imperfections that create nonradiative decay states in the middle of the optical gap. These trap states must first be filled with electronic carriers before steady PL can be achieved.…”