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Perovskite solar cells (PSCs) have reached a formidable power conversion efficiency of 25.7% over the years of development. One of the strategies that has been responsible for the development of stable and highly efficient PSCs is modifications of the monovalent A‐site cations (methylammonium, MA; formamidinium, FA; cesium, Cs, etc.) in lead halide perovskites. Herein, the impact of modifying the monovalent cation (MA, FAMA, CsFAMA, potassium‐passivated CsFAMA, rubidium‐passivated CsFAMA) in lead halide perovskite on their optoelectronic, charge transport, and photovoltaic behavior is systematically studied. Reduced trap density and improved charge carrier mobility after introduction of FA and Cs in the MAPb(I0.85Br0.15)3 system are confirmed. Further passivation of the triple‐cation perovskite with K and Rb enhances the optoelectronic characteristics, charge transport, and charge extraction efficiency in halide perovskite solar cells. [ABSTRACT FROM AUTHOR]

Perovskite-based optoelectronic devices are gaining much attention owing to their remarkable performance and low processing cost, particularly for solar cells. However, for perovskite light-emitting diodes, non-radiative charge recombination has limited the electroluminescence efficiency. Here we demonstrate perovskite-polymer bulk heterostructure light-emitting diodes exhibiting external quantum efficiencies of up to 20.1% (at current densities of 0.1-1 mA cm−2). The light-emitting diode emissive layer comprises quasi-two-dimensional and three-dimensional (2D/3D) perovskites and an insulating polymer. Photogenerated excitations migrate from quasi-2D to lower-energy sites within 1 ps, followed by radiative bimolecular recombination in the 3D regions. From near-unity external photoluminescence quantum efficiencies and transient kinetics of the emissive layer with and without charge-transport contacts, we find non-radiative recombination pathways to be effectively eliminated, consistent with optical models giving near 100% internal quantum efficiencies. Although the device brightness and stability (T50 = 46 h in air at peak external quantum efficiency) require further improvement, our results indicate the significant potential of perovskite-based photon sources. Near-infrared perovskite-polymer light-emitting diodes (LEDs) with external quantum efficiencies of up to 20.1% are reported. [ABSTRACT FROM AUTHOR]

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 increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications. [ABSTRACT FROM AUTHOR]

Herein, the impact of modifying the monovalent cation in lead halide perovskite on their optoelectronic and charge transport behavior is systematically studied. Reduced trap density and improved charge carrier mobility after introduction of formamidinium and Cs in the MAPbI0.85Br0.15 system are confirmed. Further passivation with potassium and rubidium enhances the optoelectronic characteristics and charge transport in perovskite solar cells. More details can be found in article number 2300358, Mojtaba Abdi‐Jalebi and co‐workers. [ABSTRACT FROM AUTHOR]

Impact of A-Site Cation Modification on Charge Transport Properties of Lead Halide Perovskite for Photovoltaics Applications Further passivation with potassium and rubidium enhances the optoelectronic characteristics and charge transport in perovskite solar cells. Herein, the impact of modifying the monovalent cation in lead halide perovskite on their optoelectronic and charge transport behavior is systematically studied. [Extracted from the article]

Scanning nanofocus X-ray diffraction (nXRD) performed at a synchrotron is used to simultaneously probe the morphology and the structural properties of spin-coated CH3NH3PbI3 (MAPI) perovskite films for photovoltaic devices. MAPI films are spin-coated on a Si/SiO2/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) substrate held at different temperatures during the deposition in order to tune the perovskite film coverage. The films are then investigated using nXRD and scanning electron microscopy (SEM). The advantages of nXRD over SEM and other techniques are discussed. A method to visualize, selectively isolate, and structurally characterize single perovskite grains buried within a complex, polycrystalline film is developed. The results of nXRD measurements are correlated with solar cell device measurements, and it is shown that spin-coating the perovskite precursor solution at elevated temperatures leads to improved surface coverage and enhanced solar cell performance. [ABSTRACT FROM AUTHOR]

The effect of incorporating 2.85 nm red luminescent silicon nanoparticles as photoluminescence down-shifters on the efficiency of organic solar cells based on regioregular poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl-C71-butyric acid methyl ester is investigated. The silicon nanoparticles are deposited by spin coating and inkjet printing on different layers of the devices. The presence of the silicon nanoparticles in the organic solar cells does not result in any performance improvement and causes a significant degradation of the power conversion efficiency. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

On page 8221, S. Lilliu and co‐workers show how synchrotron nXRD can be used to simultaneously probe the morphology and the structural properties of spin‐coated CH3NH3PbI3 perovskite films for photovoltaic devices. A method to visualize, selectively isolate, and structurally characterize single perovskite grains buried within a complex, polycrystalline film is developed. [ABSTRACT FROM AUTHOR]

A correction to the article "Detrimental Effect of Silicon Nanoparticles on P3HT:PCBM-Based OPV Devices" published in a previous issue is presented.

The incorporation of noble metal nanoparticles, displaying localized surface plasmon resonance, in the active area of donor-acceptor bulk-heterojunction organic photovoltaic devices is an industrially compatible light trapping strategy, able to guarantee better absorption of the incident photons and give an efficiency improvement between 12% and 38%. In the present work, we investigate the effect of Au and Ag nanoparticles blended with P3HT: PCBM on the P3HT crystallization dynamics by synchrotron grazing incidence X-ray diffraction. We conclude that the presence of (1) 80 nm Au, (2) mix of 5 nm, 50 nm, 80 nm Au, (3) 40 nm Ag, and (4) 10 nm, 40 nm, 60 nm Ag colloidal nanoparticles, at different concentrations below 0.3 wt% for Au and below 0.1% for Ag in P3HT: PCBM blends, does not affect the behaviour of the blends themselves. [ABSTRACT FROM AUTHOR]