Charge Carrier Dynamics upon Sub-bandgap Excitation in Methylammonium Lead Iodide Thin Films: Effects of Urbach Tail, Deep Defects, and Two-Photon Absorption

To further understand the optoelectronic properties of metal halide perovskites, we investigate sub-bandgap absorption in methylammonium lead iodide (MAPbI3) films. Charge carrier dynamics are studied using time-resolved microwave conductivity measurements using sub-bandgap excitation. From changes in the decay dynamics as a function of...

Crystal orientation and grain size: Do they determine optoelectronic properties of MAPbI₃ Perovskite?

Growing large, oriented grains of perovskite often leads to efficient devices, but it is unclear if properties of the grains are responsible for the efficiency. Domains observed in SEM are commonly misidentified with crystallographic grains, but SEM images do not provide diffraction information. We study methylammoinium lead iodide (MAPbI<sub...

Charge Carriers Are Not Affected by the Relatively Slow-Rotating Methylammonium Cations in Lead Halide Perovskite Thin Films

Recently, several studies have investigated dielectric properties as a possible origin of the exceptional optoelectronic properties of metal halide perovskites (MHPs). In this study we investigated the temperature-dependent dielectric behavior of different MHP films at different frequencies. In the gigahertz regime, dielectric losses in...

Comparing the Calculated Fermi Level Splitting with the Open-Circuit Voltage in Various Perovskite Cells

While the power conversion efficiency of metal halide perovskite (MHP) solar cells has increased enormously, the open-circuit voltage, V _oc , is still below the conceivable limit. Here, we derive the Fermi level splitting, μ _F , for various types of noncontacted MHPs, which sets a limit for their achievable V <sub>oc<...

Revealing the Fate of Photo-Generated Charges in Metal Halide Perovskites

In this thesis, we have investigated the optoelectronic properties of metal halide perovskites with a special focus on their application in solar cells. In less than a decade of development, metal halide perovskites have yielded solar cells with efficiencies comparable to commercialized technologies. However, there has been limited knowledge...

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to...

Thermally Activated Second-Order Recombination Hints toward Indirect Recombination in Fully Inorganic CsPbI₃ Perovskites

The relationship between the dipole moment of the methylammonium cation and the optoelectronic properties of lead halide perovskites remains under debate. We show that both the temperature-dependent charge carrier mobility and recombination kinetics are identical for methylammonium and cesium lead iodide, indicating that the role of the...

Band-Like Charge Transport in Cs₂AgBiBr₆ and Mixed Antimony-Bismuth Cs₂AgBi_{1- x}Sb_xBr₆ Halide Double Perovskites

Recently, halide double perovskites (HDPs), such as Cs₂AgBiBr₆, have been reported as promising nontoxic alternatives to lead halide perovskites. However, it remains unclear whether the charge-transport properties of these materials are as favorable as for lead-based perovskites. In this work, we study the mobilities of...

Interconversion between Free Charges and Bound Excitons in 2D Hybrid Lead Halide Perovskites

The optoelectronic properties of hybrid perovskites can be easily tailored by varying their components. Specifically, mixing the common short organic cation (methylammonium (MA)) with a larger one (e.g., butyl ammonium (BA)) results in 2-dimensional perovskites with varying thicknesses of inorganic layers separated by the large organic cation...

Photoluminescence from Radiative Surface States and Excitons in Methylammonium Lead Bromide Perovskites

In view of its band gap of 2.2 eV and its stability, methylammonium lead bromide (MAPbBr₃) is a possible candidate to serve as a light absorber in a subcell of a multijunction solar cell. Using complementary temperature-dependent time-resolved microwave conductance (TRMC) and photoluminescence (TRPL) measurements, we demonstrate...

Metal Halide Perovskite Polycrystalline Films Exhibiting Properties of Single Crystals

Metal halide perovskites are generating enormous excitement for use in solar cells and light-emission applications, but devices still show substantial non-radiative losses. Here, we show that by combining light and atmospheric treatments, we can increase the internal luminescence quantum efficiencies of polycrystalline perovskite films from 1...

Vapour-Deposited Cesium Lead Iodide Perovskites: Microsecond Charge Carrier Lifetimes and Enhanced Photovoltaic Performance

Metal halide perovskites such as methylammonium lead iodide (MAPbI3) are highly promising materials for photovoltaics. However, the relationship between the organic nature of the cation and the optoelectronic quality remains debated. In this work, we investigate the optoelectronic properties of fully inorganic vapour-deposited and spin-coated...

Direct-indirect character of the bandgap in methylammonium lead iodide perovskite

Metal halide perovskites such as methylammonium lead iodide (CH₃ NH₃ PbI₃) are generating great excitement due to their outstanding optoelectronic properties, which lend them to application in high-efficiency solar cells and light-emission devices. However, there is currently debate over what drives the second...