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Electrical generation and transduction of polarized electron spins in semiconductors are of central interest in spintronics and quantum information science. While spin generation in semiconductors has been frequently realized via electrical injection from a ferromagnet, there are significant advantages in nonmagnetic pathways of creating spin polarization. One such pathway exploits the interplay of electron spin with chirality in electronic structures or real space. Here, utilizing chirality‐induced spin selectivity (CISS), we demonstrate efficient creation of spin accumulation inn‐doped GaAs via electric current injection from a normal metal (Au) electrode through a self‐assembled monolayer of chiral molecules (α‐helix L‐polyalanine, AHPA‐L). The resulting spin polarization is detected as a Hanle effect in then‐GaAs, which is found to obey a distinct universal scaling with temperature and bias current consistent with chirality‐induced spin accumulation. The experiment constitutes a definitive observation of CISS in a fully nonmagnetic device structure and demonstration of its ability to generate spin accumulation in a conventional semiconductor. The results thus place key constraints on the physical mechanism of CISS and present a new scheme for magnet‐free semiconductor spintronics.

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Abstract Electroluminescence efficiencies and stabilities of quasi-two-dimensional halide perovskites are restricted by the formation of multiple-quantum-well structures with broad and uncontrollable phase distributions. Here, we report a ligand design strategy to substantially suppress diffusion-limited phase disproportionation, thereby enabling better phase control. We demonstrate that extending the π-conjugation length and increasing the cross-sectional area of the ligand enables perovskite thin films with dramatically suppressed ion transport, narrowed phase distributions, reduced defect densities, and enhanced radiative recombination efficiencies. Consequently, we achieved efficient and stable deep-red light-emitting diodes with a peak external quantum efficiency of 26.3% (average 22.9% among 70 devices and cross-checked) and a half-life of ~220 and 2.8 h under a constant current density of 0.1 and 12 mA/cm 2 , respectively. Our devices also exhibit wide wavelength tunability and improved spectral and phase stability compared with existing perovskite light-emitting diodes. These discoveries provide critical insights into the molecular design and crystallization kinetics of low-dimensional perovskite semiconductors for light-emitting devices. 

Halide perovskites, such as methylammonium lead halide perovskites (${\mathrm{MAPbX}}_3$,$\mathrm{X}=\mathrm{I}$, Br, and Cl), are emerging as promising candidates for a wide range of optoelectronic applications, including solar cells, light-emitting diodes, and photodetectors, due to their superior optoelectronic properties. All-inorganic lead halide perovskites${\mathrm{CsPbX}}_3$are attracting a lot of attention because replacing the organic cations with${\mathrm{Cs}}^{+}$enhances the stability, and its halide-mixing derivatives offer broad bandgap tunability covering nearly the entire visible spectrum. However, there is evidence suggesting that the optical properties of mixed-halide perovskites are influenced by phase segregation under external stimuli, especially illumination, which may negatively impact the performance of optoelectronic devices. It is reported that the mixed-halide perovskites in forms of thin films and nanocrystals are segregated into a low-bandgap I-rich phase and a high-bandgap Br-rich phase. Herein, we present a critical review on the synthesis and basic properties of all-inorganic perovskites, phase-segregation phenomena, plausible mechanisms, and methods to mitigate phase segregation, providing insights on advancing mixed-halide perovskite optoelectronics with reliable performance.

 

Perovskite light‐emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi‐2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light‐emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi‐2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi‐2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi‐2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m⁻²and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs.