Molecular passivation of MAPbI3 perovskite films follows the Langmuir adsorption rule

Abstract

Surface defect passivation through additional molecular bonding plays a crucial role in optimization of perovskite-based photovoltaic devices. So far, quantization of the defect site coverage by molecular passivation remains unclear from a macroscopic view. We herein unravel the coverage possibility of the surface defect sites of perovskite films by the added molecule passivators upon an MAPbI3 perovskite system. Concerns of inconsistent time-resolved photoluminescence (TRPL) spectroscopic measurements are dispelled by vapor-deposition fabrications of highly uniform perovskite films. The surface defect densities of perovskite films are derived from global fittings of the charge carrier dynamics to the measured TRPL decays. It is revealed the Langmuir adsorption relationship of the defect site coverage with respect to the added amount of tri-n-octylphosphine oxide passivation molecules. Our work supplements the dynamical bonding model of the molecular passivation process and provides reliable knowledge upon the bonding process between molecules and defects, which leads to rationalized surface passivation methodologies in perovskite photovoltaics communities.

Fully Textured, Production‐Line Compatible Monolithic Perovskite/Silicon Tandem Solar Cells Approaching 29% Efficiency

“…Carrier dynamics fittings were also applied to the PL decays by using surface recombination velocity (SRV) to describe the loss rate of carriers at interface, as based on our previous works. [45,46] Detailed simulation and fitting procedures are provided in Supporting Information. Results suggest an SRV of 150 cm s −1 for NiO x /2PACz that is consistently one order of magnitude lower than the NiO x -only sample (2000 cm s −1 ), in line with the comparison of the defect densities between both samples as measured by tDOS.…”

Microwave-facilitated crystal growth of defect-passivated triple-cation metal halide perovskites toward efficient solar cells

“…Such types of Lewis bases have been reported to reduce the dangling bond density by establishing Pb-O bonds, which eliminates the ionic defects of Pb 2+ ions. [23][24][25] Among them, TOPO exhibits a strong coordination ability of the oxygen atom in the PvO group to Pb 2+ ions, thereby suppressing non-radiative recombination by a reduction in ionic defects acting as trap sites. Therefore, TOPO has been an appealing defect passivator for enhancing the device performance in photovoltaics and lightemitting diodes based on metal halide perovskites, regardless of the dimensions.…”

Variation of Charge Carrier Dynamics for Polycrystalline Perovskite Films by One-Step Solution and Vapor-Deposition Methods

“…We then probe the carrier dynamics for each film by using TRPL spectroscopy. Following our previous works, ,, we introduced surface recombination velocity (SRV) to describe the boundary conditions of 1-D carrier diffusion–recombination model as given by eq . , .25ex2ex normald n ( x , t ) normald t = D ∂ 2 n ( x , t ) ∂ x 2 − k 1 n ( x , t ) − k 2 n 2 ( x , t ) D ∂ n false( x , t false) ∂ x | x = 0 = S 0 n ( 0 , t ) D ∂ n false( x , t false) ∂ x | x = L = prefix− S L n ( L , t ) …”

“…Our analysis is based on time-resolved photoluminescence spectroscopy (TRPL) measurements combining simulation of the carrier diffusion–recombination process. First, in order to secure the reliability of TRPL measurements, we fabricated MAPbI 3 perovskite films with special care on the uniformity in terms of the consistent PL decays over the film, following our previous works. − We particularly denote the air-contact surface of the film as the top-side and the buried contact with the substrate as the bottom-side in the following context. The solution-processed films were prepared using the one-step spin-coating method, and the vapor-deposited films were realized by a dual-source coevaporation process, as illustrated in Scheme .…”

“…We then probe the carrier dynamics for each film by using TRPL spectroscopy. Following our previous works, ,, we introduced surface recombination velocity (SRV) to describe the boundary conditions of 1-D carrier diffusion–recombination model as given by eq . , where n ( x , t ) is the charge carrier density, D is the diffusion coefficient, k 1 and k 2 correspond to the widely known monomolecular and germinate recombination rates, respectively, and S 0 and S L are top- and bottom-SRVs, respectively.…”