Colloidal quantum dots (CQDs) offer promise in flexible electronics, light sensing and energy conversion. These applications rely on rectifying junctions that require the creation of high-quality CQD solids that are controllably n-type (electron-rich) or p-type (hole-rich). Unfortunately, n-type semiconductors made using soft matter are notoriously prone to oxidation within minutes of air exposure. Here we report high-performance, air-stable n-type CQD solids. Using density functional theory we identify inorganic passivants that bind strongly to the CQD surface and repel oxidative attack. A materials processing strategy that wards off strong protic attack by polar solvents enabled the synthesis of an air-stable n-type PbS CQD solid. This material was used to build an air-processed inverted quantum junction device, which shows the highest current density from any CQD solar cell and a solar power conversion efficiency as high as 8%. We also feature the n-type CQD solid in the rapid, sensitive, and specific detection of atmospheric NO2. This work paves the way for new families of electronic devices that leverage air-stable quantum-tuned materials.

In this work, we describe details of a two-step deposition approach that enables the preparation of continuous and well-structured thin films of Cs 2 SnI 6 , which is a one-half Sndeficient 0-D perovskite derivative (i.e., the compound can also be written as CsSn 0.5 I 3 , with a structure consisting of isolated SnI 6 4− octahedra). The films were characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), UV−vis spectroscopy, photoluminescence (PL), photoelectron spectroscopy (UPS, IPES, XPS), and Hall effect measurements. UV−vis and PL measurements indicate that the obtained Cs 2 SnI 6 film is a semiconductor with a band gap of 1.6 eV. This band gap was further confirmed by the UPS and IPES spectra, which were well reproduced by the calculated density of states with the HSE hybrid functional. The Cs 2 SnI 6 films exhibited n-type conduction with a carrier density of 6(1) × 10 16 cm −3 and mobility of 2.9(3) cm 2 /V•s. While the computationally derived band structure for Cs 2 SnI 6 shows significant dispersion along several directions in the Brillouin zone near the band edges, the valence band is relatively flat along the Γ−X direction, indicative of a more limited hole minority carrier mobility compared to analogous values for the electrons. The ionization potential (IP) and electron affinity (EA) were determined to be 6.4 and 4.8 eV, respectively. The Cs 2 SnI 6 films show some enhanced stability under ambient air, compared to methylammonium lead(II) iodide perovskite films stored under similar conditions; however, the films do decompose slowly, yielding a CsI impurity. These findings are discussed in the context of suitability of Cs 2 SnI 6 for photovoltaic and related optoelectronic applications.

Organic, planar, and electron deficient small molecules were utilized as acceptors in the first reported bilayer heterojunction solar cells, however, current state-of-the-art organic photovoltaic (OPV) cells utilize fullerene derivatives as acceptor molecules. Recently, intensive efforts have been directed towards the development and understanding of soluble, non-fullerene, organic small molecules to fabricate bulk heterojunction (BHJ) solar cells. These efforts have been aimed at overcoming the inherent limitations of fullerene compounds such as the limited spectral breadth, air instability, and the typically higher production costs of fullerenes. In this focused review, we have highlighted the most recent progress over the last couple of years towards developing n-type organic small molecules utilized in BHJ devices in order to provide insight towards improving the overall performance of OPVs. Ala'a F. Eaiha was born in Jerusalem, Palestine. He obtained his BSc and MSc in chemistry from the Hashemite University, Jordan. Ala'a carried out his graduate research under the supervision of both Dr Musa I. El-Barghouthi and Dr Adnan A. Badwan. Aer spending two years doing research at the Jordanian pharmaceutical Manufacturing Company, Jordan, he moved to Canada, where he completed his PhD in surface chemistry under the guidance of Dr Matthew F. Paige at the University of Saskatchewan. Recently, Ala'a has received an NSERC CREATE fellowship to carry out postdoctoral research at

The role of two homologous cyclic sulfate electrolyte additives, trimethylene sulfate (or 1,3,2-dioxathiane-2,2-dioxide, TMS) and ethylene sulfate (or 1,3,2-dioxathiolane-2,2-dioxide, DTD), used either alone or in combination with vinylene carbonate (VC) on the lifetime of LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC)/graphite pouch cells was studied by correlating data from gas chromatography/mass spectroscopy (GC−MS), dQ/dV analysis, ultrahigh precision coulometry, storage experiments, and X-ray photoelectron spectroscopy. For VC alone, more stable and protective SEI films were observed at the surface of both electrodes due to the formation of a polymer of VC, which results in higher capacity retention. For TMS, similar chemical SEI compositions were found compared to the TMS-free electrolytes. When VC was added to TMS, longer cell lifetime is attributed to VC. For DTD, a cell lifetime that competes with VC was explained by a preferential reduction potential and a much higher fraction of organic compounds in the SEI films. When VC was added to DTD, the contribution of both additives to the SEI films is consistent with the initial reactivity observed from dQ/dV and GC−MS analysis.

Dual-source evaporation approach is applied to deposit AgBi2I7, AgBiI4 and Ag2BiI5 films; a planar junction AgBiI4-solar cell is demonstrated.