Query: Interpreting time-resolved photoluminescence of perovskite materials

Candidate papers:

abstract: Time resolved photoluminescence (TRPL) spectroscopy is a powerful technique to investigate excited charge carrier recombinations in semiconductors and molecular systems. The analysis of the TRPL decays of many molecular systems (e.g. molecules and organic materials) is usually fairly straightfoward and can be fitted with an exponential function allowing extraction of the rate constants. Due to the non excitonic nature of charge carriers in lead halide perovskite materials coupled with the presence of localised trap states in their band gap, the TRPL of these materials is much more complicated to interpret. Here we discuss two models used in the literature to simulate charge carrier recombinations and TRPL in perovskites. These models consider the bimolecular nature of direct electron hole recombination but differ in their treatment of trap mediated recombination with one model describing trapping as a monomolecular process whereas the other as a bimolecular process between free carriers and the available trap states. In comparison, the classical analysis of perovskite TRPL decay curves (using a sum of exponentials) can lead to misinterpretation. Here we offer some recommendations for meaningful measurements of lead halide perovskite thin films. The fluence dependence as well as charge carrier accumulation due to incomplete depopulation of all photoexcited carriers between consecutive excitation pulses are discussed for both models.
author_names: Emmanuel V Pean

Stoichko D Dimitrov

Catherine S P De Castro

Matthew L Davies
title: Interpreting time resolved photoluminescence of perovskite materials.
venue: Physical chemistry chemical physics PCCP
year: 2020

abstract: The diffusion length of photogenerated carriers is a crucial parameter in semiconductors for optoelectronic applications. However, it is a challenging task to determine the diffusion length in layered nanoplatelets due to their anisotropic diffusion of photogenerated carriers and nanometer thin thickness. Here, we demonstrate a novel method to determine the in plane diffusion length of photogenerated carriers in layered nanoplatelets using local time resolved photoluminescence. An in plane carrier diffusion length of 1.82 um is obtained for an exfoliated (BA)2PbI4 (BA=CH3(CH2)3NH3) perovskite nanoplatelet. This method is particularly useful for weak luminescent materials and the materials that are easily damaged by long term laser beam because of the high detection sensitivity. This technique is extendable to other layered materials and therefore plays a valuable role in the development and optimization of 2D and 3D semiconductor materials and devices for photovoltaic and photonic applications.
author_names: Chunhua Zhou

Weijian Chen

Shuang Yang

Qingdong Ou

Zhixing Gan

Qiaoliang Bao

Baohua Jia

Xiaoming Wen
title: Determining in plane Carrier Diffusion in Two Dimensional Perovskite using local time resolved photoluminescence.
venue: ACS applied materials interfaces
year: 2020

abstract: Halide perovskite photovoltaic cells have attracted tremendous attention over recent years due to the rapid rise in solar cell efficiencies and their potential for providing high efficiency low cost solar power.1 Solar cell efficiencies have increased from 9% in 2012 to 21% in 2017 and are now competitive with traditional crystalline silicon cells.2,3 Despite this impressive rise in efficiency, the fundamental physics of these materials is not yet fully understood. In this application note time resolved photoluminescence spectroscopy will be shown to be a powerful tool for investigating and optimising the behaviour of perovskite through the measurement of charge carrier lifetimes. Introduction
title: Measuring Charge Carrier Lifetime in Halide Perovskite Using Time Resolved Photoluminescence Spectroscopy
year: 2018

abstract: Abstract We present the localization effects in orthorhombic phase of CH3NH3PbI3 perovskite materials by temperature dependent photoluminescence and time resolved photoluminescence. Our investigations indicate that the tetragonal inclusions in the orthorhombic phase of MAPbI3 at low temperature are the main reason for the formation of localization states with a depth of about 22.3 meV. The coexistence of the tetragonal and orthorhombic phases also results in an abnormal behavior of luminescence intensity from 12 to 80 K. The detailed understanding of luminescence characteristics upon the orthorhombic phase in MAPbI3 at low temperature can expand ideally the application fields of perovskite materials.
author_names: Fu Jen Cheng

S Y Hu

L Y Chen

Y C Lee

Gerald Zheyao Yin

K K Tiong

J L Shen
title: Time resolved photoluminescence studies on localization effects in orthorhombic phase of CH3NH3PbI3 perovskite thin film
year: 2018

abstract: Carrier lifetime characterization in solar cell and light emitting diode materials by time resolved photoluminescence and differential transmission is of high importance, indicating cost efficient streak camera suitable for such tests would be highly demanded. In this work an electro optic deflecting device is extended to full functionality streak camera operating in wide spectral range (200 2000 nm) by using electro optic DKDP crystals. Setup, consisting of picosecond laser for sample excitation, electro optic deflector and imaging spectrograph with silicon and InGaAs cameras, allows spectral and temporal imaging of recombination dynamics in semiconductor materials, with variable bandgap and composition (tested on metal halide perovskite crystal) achieving temporal resolution up to 50 ps. For the case of time resolved differential transmission, broadband <50 ps pulsed or CW xenon light source can be used for absorption change probing.
author_names: Patrik Scajev
title: Time resolved photoluminescence and xenon differential transmission measurement device based on electro optic deflector
venue: OPTO
year: 2021

abstract: A self powered,solution processed perovskite photodetector with sub nanosecond response time is presented. Eliminating charge trapping and removing the constraints from the resistance capacitance constant increases the response speed, which enables them to be applied in a homemade, time resolved photoluminescence system that successfully resolves the decay process of typical fluorescence and phosphorescent materials with a recombination lifetime from several nanoseconds to microseconds.
author_names: Liang Shen

Yanjun Fang

Dong Wang

Yang Bai

Yehao Deng

Mengmeng Wang

Yongfeng Lu

Jinsong Huang
title: A Self Powered, Sub nanosecond Response Solution Processed Hybrid Perovskite Photodetector for Time Resolved Photoluminescence Lifetime Detection.
venue: Advanced materials
year: 2016

abstract: In the quest for better solar panels, we continue to refine our understanding of the physics of photovoltaic absorbers, such as hybrid metal organic perovskites. By scrutinizing photoluminescence transients, the authors explain how to determine fundamental semiconductor properties and estimate the potential open circuit voltage of perovskite thin films. Additionally, they highlight the impacts of photon recycling, doping, and bulk and surface recombination of charge carriers on device performance.
author_names: Florian Staub

Hannes Hempel

Jan-Christoph Hebig

J B Mock

Ulrich Wilhelm Paetzold

Uwe Rau

Thomas Unold

Thomas Kirchartz
title: Beyond Bulk Lifetimes: Insights into Lead Halide Perovskite Films from Time Resolved Photoluminescence
year: 2016

abstract: Owing to their exceptional semiconducting properties, hybrid inorganic organic perovskites show great promise as photovoltaic absorbers. In these materials, long range diffusion of charge carriers allows for most of the photogenerated carriers to contribute to the photovoltaic efficiency. Here, time resolved photoluminescence (PL) microscopy is used to directly probe ambipolar carrier diffusion and recombination kinetics in hybrid perovskites. This technique is applied to thin films of methylammonium lead tri iodide MAPbI$_3$ obtained with two different fabrication routes, methylammonium lead tribromide (MAPbBr$_3$ and an alloy of formamidinium lead tri iodide (FAPbI$_3$ and methylammonium lead bromide FA$_{0.85}$MA$_{0.15}$Pb(I$_{0.85}$Br_${0.15}$_3$ Average diffusion coefficients in the films leading to the highest device efficiencies and longest lifetimes, i.e. in FA$_{0.85}$MA$_{0.15}$Pb(I$_{0.85}$Br$_{0.15}$_3$ and acetonitrile processed MAPbI$_3$ are found to be several orders of magnitude lower than in the other films. Further examination of the time dependence shows strong evidence for non diffusive transport. In particular, acetonitrile processed MAPbI$_3$ shows distinct diffusion regimes on short and long timescales with an effective diffusion constant varying over 2 orders of magnitude. Our results also highlight the fact that increases in carrier lifetime in this class of materials are not necessarily concomitant with increased diffusion lengths and that the PL quantum efficiency under solar cell operating conditions is a greater indication of material, and ultimately device, quality.
author_names: Aravindan Sridharan

Nakita K Noel

Hyeon Jun Hwang

Soroush Hafezian

Barry P Rand

St'ephane K'ena-Cohen
title: Time resolved imaging of non diffusive carrier transport in long lifetime halide perovskite thin films.
year: 2019

abstract: Organic inorganic halide perovskite solar cells are attracting much attention from the photovoltaic community because of their high conversion efficiencies exceeding 20% So far, intrinsic superior optoelectronic properties of this material class have been revealed through comprehensive studies on the thin films and single crystals [1,2] For further improvement of the device architecture and conversion efficiency, the carrier recombination and transport dynamics in actual solar cell devices have to be clarified. The perovskite solar cell is usually implemented as a heterojunction structure consisting of a perovskite absorber layer and charge transport layers as selective contacts, and the carrier injection properties at these heterointerfaces play a crucial role for the device performance. Time resolved photoluminescence (PL) techniques are usually adopted to investigate carrier injection and transport properties [3] However, PL is also additionally affected by traps and defects within the perovskite layer and also at the heterointerface. On the other hand, the photocurrent (PC) measurement can directly assess the net charge carrier flow through the whole device. Therefore a combination of PL and PC enables us to investigate the details of the carrier injection. In addition, perovskite solar cells are prepared by a fast and cost effective low temperature solution process, but this simple preparation method also causes a spatial nonuniformity in the optical and electrical properties [4] Thus, the spatial imaging is invaluable for statistical evaluation of the solar cell characteristics.
author_names: Taketo Handa

Daiki Yamashita

David M Tex

Ai Shimazaki

Atsushi Wakamiya

Yoshihiko Kanemitsu
title: Charge carrier injection at the heterointerface in CH3NH3PbI3 perovskite solar cells studied by time resolved photoluminescence and photocurrent imaging spectroscopy
venue: 2017 Conference on Lasers and Electro Optics Europe European Quantum Electronics Conference (CLEO/Europe EQEC)
year: 2017

abstract: While perovskite nanocrystals (NCs) have shown great promise as materials for efficient light emitting diodes (LEDs) low photoluminescence quantum yield (PLQY) of the blue emitting perovskites is an impediment to the development of white LEDs of which blue is an essential component. Herein, we report that room temperature postsynthetic treatment of weakly blue violet emitting (PLQY 3% CsPbCl3 NCs with CdCl2 results in an instantaneous enhancement of the PLQY to near unity without affecting the PL peak position (406 nm) and spectral width. The time resolved PL and ultrafast transient absorption measurements confirm the removal of nonradiative defect states of the CsPbCl3 NCs in treated sample. The elemental composition and structural data of the treated sample reveal facile doping of Cd2+ into the crystal lattice without affecting the size and shape of the NCs. Extraordinary PLQY, high air stability and photostability and ease of preparation of this Cd doped CsPbCl3 make it by far the most attractive blu.
author_names: Navendu Mondal

Apurba De

Anunay Samanta
title: Achieving Near Unity Photoluminescence Efficiency for Blue Violet Emitting Perovskite Nanocrystals
year: 2019