Hydroiodic Acid Additive Enhanced the Performance and Stability of PbS-QDs Solar Cells via Suppressing Hydroxyl Ligand.

The recent emerging progress of quantum dot ink (QD-ink) has overcome the complexity of multiple-step colloidal QD (CQD) film preparation and pronouncedly promoted the device performance. However, the detrimental hydroxyl (OH) ligands induced from synthesis procedure have not been completely removed. Here, a halide ligand additive strategy was devised to optimize QD-ink process. It simultaneously reduced sub-bandgap states and converted them into iodide-passivated surface, which increase carrier mobility of the QDs films and achieve thicker absorber with improved performances. The corresponding power conversion efficiency of this optimized device reached 10.78%. (The control device was 9.56%.) Therefore, this stratege can support as a candidate strategy to solve the QD original limitation caused by hydroxyl ligands, which is also compatible with other CQD-based optoelectronic devices.

2D Lead Dihalides for High-Performance Ultraviolet Photodetectors and their Detection Mechanism Investigation.

2D halide semiconductors, a new family of 2D materials in addition to transition metal dichalcogenides, present ultralow dark current and high light conversion yield, which hold great potential in photoconductive detectors. Herein, a facile aqueous solution method is developed for the preparation of large-scale 2D lead dihalide nanosheets (PbF2-x Ix ). High-performance UV photodetectors are successfully implemented based on 2D PbF2-x Ix nanosheets. By modulating the components of halogens, the bandgap of PbF2-x Ix nanosheets can be tuned to meet varied detection spectra. The photoresponse dependence on incident power density, wavelength, detection environment, and temperature are systematically studied to investigate their detection mechanism. For PbI2 photodetectors, they are dominantly driven by a photoconduction mechanism and show a fast response speed and a low noise current density. A high normalized detectivity of 1.5 × 1012 Jones and an ION /IOFF ratio up to 103 are reached. On the other hand, PbFI photodetectors demonstrate a photogating mechanism mediated by trap states showing high responsivity. The novel 2D halide materials with wide bandgaps, superior detection performance, and facile synthesis process can enrich the Van der Waals solids family and hold great potential for a wide variety of applications in advanced optoelectronics.

High Quantum Yield Blue Emission from Lead-Free Inorganic Antimony Halide Perovskite Colloidal Quantum Dots.

Colloidal quantum dots (QDs) of lead halide perovskite have recently received great attention owing to their remarkable performances in optoelectronic applications. However, their wide applications are hindered from toxic lead element, which is not environment- and consumer-friendly. Herein, we utilized heterovalent substitution of divalent lead (Pb2+) with trivalent antimony (Sb3+) to synthesize stable and brightly luminescent Cs3Sb2Br9 QDs. The lead-free, full-inorganic QDs were fabricated by a modified ligand-assisted reprecipitation strategy. A photoluminescence quantum yield (PLQY) was determined to be 46% at 410 nm, which was superior to that of other reported halide perovskite QDs. The PL enhancement mechanism was unraveled by surface composition derived quantum-well band structure and their large exciton binding energy. The Br-rich surface and the observed 530 meV exciton binding energy were proposed to guarantee the efficient radiative recombination. In addition, we can also tune the inorganic perovskite QD (Cs3Sb2X9) emission wavelength from 370 to 560 nm via anion exchange reactions. The developed full-inorganic lead-free Sb-perovskite QDs with high PLQY and stable emission promise great potential for efficient emission candidates.

Improving the Performance of PbS Quantum Dot Solar Cells by Optimizing ZnO Window Layer.

Comparing with hot researches in absorber layer, window layer has attracted less attention in PbS quantum dot solar cells (QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on. Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V oc of 18%, J sc of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.

Extraction of nano-silicon with activated carbons simultaneously from rice husk and their synergistic catalytic effect in counter electrodes of dye-sensitized solar cells.

The extraction of renewable energy resources particularly from earth abundant materials has always been a matter of significance in industrial products. Herein, we report a novel simultaneous extraction of nano-silicon with activated carbons (nano-Si@ACs) from rice husk (RH) by chemical activation method. As-extracted nano-Si@ACs is then used as an energy harvesting materials in counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). The morphology, structure and texture studies confirm the high surface area, abundant active sites and porous structure of nano-Si@ACs. Electrochemical impedance spectroscopy and cyclic voltammetry analyses reveal that the nano-Si@ACs is highly beneficial for fast I3- reduction and superior electrolyte diffusion capability. The nano-Si@ACs CE based DSSC exhibits enhanced power conversion efficiency of (8.01%) in contrast to pristine Pt CE (7.20%). These favorable results highlight the potential application of RH in low-cost, high-efficiency and Pt-free DSSCs.