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Metal‐halide perovskites have proven to be a versatile group of semiconductors for optoelectronic applications, with ease of bandgap tuning and stability improvements enabled by halide and cation mixing. However, such compositional variations can be accompanied by significant changes in their charge‐carrier transport and recombination regimes that are still not fully understood. Here, a novel combinatorial technique is presented to disentangle such dynamic processes over a wide range of temperatures, based on transient free‐space, high‐frequency microwave conductivity and photoluminescence measurements conducted simultaneously in situ. Such measurements are used to reveal and contrast the dominant charge‐carrier recombination pathways for a range of key compositions: prototypical methylammonium lead iodide perovskite (MAPbI3), the stable mixed formamidinium‐caesium lead‐halide perovskite FA0.83Cs0.17PbBr0.6I2.4 targeted for photovoltaic tandems with silicon, and fully inorganic wide‐bandgap CsPbBr3 aimed toward light sources and X‐ray detector applications. The changes in charge‐carrier dynamics in FA0.83Cs0.17PbBr0.6I2.4 across temperatures are shown to be dominated by radiative processes, while those in MAPbI3 are governed by energetic disorder at low temperatures, low‐bandgap minority‐phase inclusions around the phase transition, and non‐radiative processes at room temperature. In contrast, CsPbBr3 exhibits significant charge‐carrier trapping at low and high temperatures, highlighting the need for improvement of material processing techniques for wide‐bandgap perovskites. [ABSTRACT FROM AUTHOR]

Owing to the bandgap‐bowing effect, mixed lead‐tin halide perovskites provide ideal bandgaps for the bottom subcell of all‐perovskite tandem photovoltaic devices that offer fundamentally elevated power‐conversion efficiencies. However, these materials suffer from degradation in ambient air, which worsens their optoelectronic properties and hinders their usability for photovoltaic applications. Such degradation pathways are not yet fully understood, especially for the perovskites in the middle of the APbxSn1‐xI3 solid solution line, which offer the narrowest bandgaps across the range. This study unravels the degradation mechanisms of APbxSn1‐xI3 perovskites, reporting clear differences between mixed lead‐tin (x = 0.5) and tin‐only (x = 0) perovskites. The dynamic optoelectronic properties, electronic structure, crystal structure, and decomposition products of the perovskite thin films are examined in situ during air exposure. Both perovskite compositions suffer from the formation of defects over the timescale of hours, as indicated by a significant reduction in their charge‐carrier diffusion lengths. For tin‐only perovskite, degradation predominantly causes the formation of energetically shallow tin vacancies and hole doping. However, for mixed lead‐tin perovskite, deep trap states are formed that significantly accelerate charge‐carrier recombination, yet leave mobilities relatively unaffected. These findings highlight the need for passivation strategies tailored specifically to mixed lead‐tin iodide perovskites. [ABSTRACT FROM AUTHOR]

Silver‐bismuth based semiconductors represent a promising new class of materials for optoelectronic applications because of their high stability, all‐inorganic composition, and advantageous optoelectronic properties. In this study, charge‐carrier dynamics and transport properties are investigated across five compositions along the AgBiI4–CuI solid solution line (stoichiometry Cu4x(AgBi)1−xI4). The presence of a close‐packed iodide sublattice is found to provide a good backbone for general semiconducting properties across all of these materials, whose optoelectronic properties are found to improve markedly with increasing copper content, which enhances photoluminescence intensity and charge‐carrier transport. Photoluminescence and photoexcitation‐energy‐dependent terahertz photoconductivity measurements reveal that this enhanced charge‐carrier transport derives from reduced cation disorder and improved electronic connectivity owing to the presence of Cu+. Further, increased Cu+ content enhances the band curvature around the valence band maximum, resulting in lower charge‐carrier effective masses, reduced exciton binding energies, and higher mobilities. Finally, ultrafast charge‐carrier localization is observed upon pulsed photoexcitation across all compositions investigated, lowering the charge‐carrier mobility and leading to Langevin‐like bimolecular recombination. This process is concluded to be intrinsically linked to the presence of silver and bismuth, and strategies to tailor or mitigate the effect are proposed and discussed. [ABSTRACT FROM AUTHOR]

The efficiency and longevity of metal-halide perovskite solar cells are typically dictated by nonradiative defect-mediated charge recombination. In this work, we demonstrate a vapor-based amino-silane passivation that reduces photovoltage deficits to around 100 millivolts (>90% of the thermodynamic limit) in perovskite solar cells of bandgaps between 1.6 and 1.8 electron volts, which is crucial for tandem applications. A primary-, secondary-, or tertiary-amino-silane alone negatively or barely affected perovskite crystallinity and charge transport, but amino-silanes that incorporate primary and secondary amines yield up to a 60-fold increase in photoluminescence quantum yield and preserve long-range conduction. Amino-silane-treated devices retained 95% power conversion efficiency for more than 1500 hours under full-spectrum sunlight at 85°C and open-circuit conditions in ambient air with a relative humidity of 50 to 60%.

Successful chemical doping of metal halide perovskites with small amounts of heterovalent metals has attracted recent research attention because of its potential to improve long-term material stability and tune absorption spectra. However, some additives have been observed to impact negatively on optoelectronic properties, highlighting the importance of understanding charge-carrier behavior in doped metal halide perovskites. Here, we present an investigation of charge-carrier trapping and conduction in films of MAPbBr 3 perovskite chemically doped with bismuth. We find that the addition of bismuth has no effect on either the band gap or exciton binding energy of the MAPbBr 3 host. However, we observe a substantial enhancement of electron-trapping defects upon bismuth doping, which results in an ultrafast charge-carrier decay component, enhanced infrared emission, and a notable decrease of charge-carrier mobility. We propose that such defects arise from the current approach to Bi-doping through addition of BiBr 3 , which may enhance the presence of bromide interstitials.