Lead halide perovskite quantum dots (QDs) possess color-tunable and narrow-band emissions and are very promising for lighting and display applications, but they suffer from lead toxicity and instability. Although lead-free Bi-based and Sn-based perovskite QDs (CsSnX3, Cs2SnX6 and (CH3NH3)3Bi2X9) have been reported, they all showed low photoluminescence quantum yield (PLQY) and poor stability. Here we report the synthesis of Cs3Bi2Br9 perovskite QDs with high PLQY and excellent stability. Via a green and facile process using ethanol as the anti-solvent, as-synthesized Cs3Bi2Br9 QDs show a blue emission at 410 nm with a PLQY up to 19.4%. The whole series of Cs3Bi2X9 (X = Cl, Br, I) QDs by mixing precursors could cover the PL emission range from 393 to 545 nm. Furthermore, Cs3Bi2Br9 QDs show excellent photostability and moisture stability due to the all-inorganic nature and the surface passivation by BiOBr, which enables the one-pot This article is protected by copyright. All rights reserved. 3 synthesis of Cs3Bi2Br9 QDs/silica composite. A lead-free perovskite white light emitting diode (W-LED) is fabricated by simply combine the composite of Cs3Bi2Br9 QDs/silica with Y3Al5O12 (YAG) phosphor. As a new member of lead-free perovskite QDs, Cs3Bi2Br9 QDs open up a new route for the fabrication of optoelectronic devices due to their excellent stability and photophysical characteristics.

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Metal halide perovskite quantum dots (QDs) recently have attracted great research attentions. However, blue-emitting perovskite QDs generally suffer from low photoluminescence quantum yield (PLQY) because of easily formed defects and insufficient surface passivation. Replacement of lead with low toxicity elements is also preferred toward potential commercial applications. Here, we apply Cl-passivation to boost the PLQY of MABiBr QDs to 54.1% at the wavelength of 422 nm, a new PLQY record for blue emissive, lead-free perovskite QDs. Because of the incompatible crystal structures between MABiBr and MABiCl and the careful kinetic control during the synthesis, Cl anions are engineered to mainly locate on the surface of QDs acting as passivating ligands, which effectively suppress surface defects and enhance the PLQY. Our results highlight the potential of MABiBr QDs for applications of phosphors, scintillators, and light-emitting diodes.

Defects present in the absorber layer largely dictate photovoltaic device performance. Recently, a binary photovoltaic material, Sb2Se3, has drawn much attention due to its low‐cost and nontoxic constituents and rapid performance promotion. So far, however, the intrinsic defects of Sb2Se3 remain elusive. Here, through a combined theoretical and experimental investigation, we revealed that shallow acceptors, SeSb antisites, are the dominant defects in Sb2Se3 produced in an Se‐rich environment, where deep donors, SbSe and VSe, dominate in Sb2Se3 produced in an Se‐poor environment. We further constructed a superstrate CdS/Sb2Se3 thin‐film solar cell achieving 5.76% efficiency through in situ Se compensation during Sb2Se3 evaporation and through careful optimization of absorber layer thickness. The understanding of intrinsic defects in Sb2Se3 film and the demonstrated success of in situ Se compensation strategy pave the way for further efficiency improvement of this very promising photovoltaic technology. Copyright © 2017 John Wiley & Sons, Ltd.

Sb 2 Se 3 is a promising candidate for thin-film photovoltaics, with a suitable band gap, benign grain boundaries, Earth-abundant and nontoxic constituents, and excellent stability. However, the low doping density (10 13 cm −3 ) of Sb 2 Se 3 absorber and back contact barrier limit its efficiency. Here we introduced a PbS colloidal quantum dot (CQD) film as the hole-transporting layer (HTL) to construct a n-i-p configured device and overcame these problems. Through simulation-guided optimization, we have significantly improved the efficiency of a Sb 2 Se 3 thin-film solar cell to a new certified record of 6.5%. The PbS CQD HTL not only minimized carrier recombination loss at the back contact and boosted carrier collection efficiency but also contributed photocurrent by its own nearinfrared absorption. Furthermore, these n-i-p devices also demonstrated improved device uniformity, achieving 6.39% in a 1.02 cm 2 device.

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The binary semiconductor of antimony selenide (Sb 2 Se 3 ) has received wide attention as potential solar cell absorber material recently due to its attractive optoelectronic properties such as proper bandgap (1.17 eV direct and 1.03 eV indirect), large absorption coefficient (>10 5 cm −1 ), decent carrier mobility (≈10 cm 2 V −1 s −1 ), and long carrier lifetime (≈60 ns) as well as its low toxicity, low cost, and earth-abundant constituents. [1] Based on the rapid thermal evaporation (RTE) deposition technology, power conversion efficiencies (PCE) were achieved in superstrate CdS-based Sb 2 Se 3 and Sb 2 (S x ,Se 1−x ) 3 thin film solar cells as 5.6% and 5.79%, [2] respectively. Simultaneously, the substrate Sb 2 Se 3 solar cells with CdS buffer layer were also rapidly developed with PCE over 4% reported by several groups. [3] The traditional CdS buffer layer is toxic to human and environment, and the device reveals low

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