Synergetic Exterior and Interfacial Approaches by Colloidal Carbon Quantum Dots for More Stable Perovskite Solar Cells Against UV.

The achievement of both efficiency and stability in perovskite solar cells (PSCs) remains a challenging and actively researched topic. In particular, among different environmental factors, ultraviolet (UV) photons play a pivotal role in contributing to device degradation. In this work, by harvesting simultaneously both the optical and the structural properties of bottom-up-synthesized colloidal carbon quantum dots (CQDs), a cost-effective means is provided to circumvent the UV-induced degradation in PSCs without scarification on their power conversion efficiencies (PCEs). By exploring and optimizing the number of CQDs and the different locations/interfaces of the solar cells where CQDs are applied, a synergetic configuration is achieved where the photovoltaic performance drop due to optical loss is completely compensated by the increased perovskite crystallinity due to interfacial modification. As a result, on the optimized configurations where CQDs are applied both on the exterior front side as an optical layer and at the interface between the electron transport layer and the perovskite absorber, unencapsulated PSCs with PCEs >20% are fabricated which can maintain up to ≈94% of their initial PCE after 100 h of degradation in ambient air under continuous UV illumination (5 mW cm-2).

Dicopper(I) Complexes Incorporating Acetylide-Functionalized Pyridinyl-Based Ligands: Synthesis, Structural, and Photovoltaic Studies.

Heteroaryl incorporated acetylide-functionalized pyridinyl ligands (L1-L6) with the general formula Py-C≡C-Ar (Py = pyridine and Ar = thiophene-2-yl, 2,2' -bithiophene]-5-yl, 2,2' :5',2″ -terthiophene]-5-yl, thieno[2,3- b]thiophen-2-yl, quinoline-5-yl, benzo[c][1,2,5]thiadiazole-5-yl) have been synthesized by Pd(0)/Cu(I)-catalyzed cross-coupling reaction of 4-ethynylpyridine and the respective heteroaryl halide. Ligands L1-L6 were isolated in respectable yields and characterized by microanalysis, IR spectroscopy, 1H NMR spectroscopy, and ESI-MS mass spectrometry. A series of dinuclear Cu(I) complexes 1-10 have been synthesized by reacting L1-L6 with CuI and triphenylphosphine (PPh3) (R1) or with an anchored phosphine derivative, 4-(diphenylphosphino) benzoic acid (R2)/2-(diphenylphosphino)benzenesulfonic acid (R3), in a stoichiometric ratio. The complexes are soluble in common organic solvents and have been characterized by analytical, spectroscopic, and computational methods. Single-crystal X-ray structure analysis confirmed rhomboid dimeric structures for complexes 1, 2, 4, and 5, and a polymeric structure for 6. Complexes 1-6 showed oxidation potential responses close to 0.9 V vs Fc0/+, which were chemically irreversible and are likely to be associated with multiple steps and core oxidation. Preliminary photovoltaic (PV) results of these new materials indicated moderate power conversion efficiency (PCE) in the range of 0.15-1.56% in dye-sensitized solar cells (DSSCs). The highest PCE was achieved with complex 10 bearing the sulfonic acid anchoring functionality.

Long-Term Stable Near-Infrared-Short-Wave-Infrared Photodetector Driven by the Photothermal Effect of Polypyrrole Nanostructures.

Polypyrrole (PPy) is a conductive polymer and widely applied in different applications owing to its broadband absorption in the UV-visible, near-infrared (NIR), and short-wave-infrared (SWIR) spectrum, excellent conductivity, and strong photothermal effect. In this work, we explored for the first time the photothermal effect of PPy nanoparticles (PPy-NPs) in a photothermal-induced detector structure and developed a new type of air-stable hybrid PPy-NPs/Pt photodetector (PD) with NIR/SWIR sensitivity. By combining PPy-NPs with a platinum (Pt)-resistive pattern, we fabricated PPy-NPs/Pt PDs that are sensitive to illumination in the wavelength range from 800 to 2000 nm. Under the illumination of λ = 1.5 µm, the maximum photoresponsivity was measured to be ∼1.3 A/W with a 131 µs photoresponse rise time. Owing to the excellent material stability from both PPy-NPs and the Pt pattern, the current photodetectors show long-term stable photoresponsivity when they were stored in air without encapsulation. The results suggest that the PPy-NPs/Pt hybrid PDs are promising candidates for a new type of low-cost and broadband due to their multiple advantages such as free of toxic heavy metals, air stability, and solution processing.