Improved efficiency and photo-stability of methylamine-free perovskite solar cells via cadmium doping

Although perovskite solar cells containing methylamine cation can show high power conversion efficiency,stability is a concern.Here,methylamine-free perovskite material Csx FA1–x PbI3 was synthesized by a one-step method.In addition,we incorporated smaller cadmium ions into mixed perovskite lattice to partially replace Pb ions to address the excessive internal strain in perovskite structure.We have found that the introduction of Cd can improve the crystallinity and the charge carrier lifetime of perovskite films.Consequently,a power conversion efficiency as high as 20.59%was achieved.More importantly,the devices retained 94%of their initial efficiency under 1200 h of continuous illumination.

Photo-stability of CsPbBr_3 perovskite quantum dots for optoelectronic application

Due to their superior photoluminescence(PL)quantum yield(QY) and tunable optical band gap,all-inorganic CsPbBr_3 perovskite quantum dots(QDs) have attracted intensive attention for the application in solar cells,light emitting diodes(LED),photodetectors and laser devices.In this scenario,the stability of such materials becomes a critical factor to be revealed.We hereby investigated the long-term stability of as-synthesized CsPbBr_3 QDs suspended in toluene at various environmental conditions.We found light illumination would induce drastic photo-degradation of CsPbBr_3 QDs.The steady-state spectroscopy,transmission electron microscopy(TEM),and X-ray diffraction(XRD)verified that CsPbBr_3 QDs tend to aggregate to form larger particles under continuous light soaking.In addition,decreasing PL QY of the QDs during light soaking indicates the formation of trap sites.Our work reveals that the main origin of instability in CsPbBr_3 QDs and provides reference to engineer such QDs towards optimal device application.

Tailoring electrical property of the low-temperature processed SnO_2 for high-performance perovskite solar cells

Herein, we for the first time doped Nb^5+into the low-temperature(<100°C) SnO2sol-gel route to tailor the electrical property of SnO2 layers and the band alignment between SnO2 and the normally used mixed perovskites. The results revealed that proper Nb5+doping increased the conductivity of the SnO2 electron transport layer(ETL), and the conduction band(CB) level of the SnO2 ETL was shifted down to approach the CB level of perovskites, which facilitated the electron injection from perovskite to SnO2, accelerated the charge transport, and reduced the non-radiative recombination, leading to improved power conversion efficiency from18.06% to 19.38%. The Nb^5+doping process provided an efficient route for fabricating high-efficiency perovskite solar cells(PSCs) at a temperature lower than 100°C, and promoted the commercialization progress of PSCs.

Intrinsically inert hyperbranched interlayer for enhanced stability of organic solar cells

Device stability becomes one of the most crucial issues for the commercialization of organic solar cells(OSCs) after high power conversion efficiencies have been achieved. Besides the intrinsic stability of photoactive materials, the chemical/catalytic reaction between interfacial materials and photoactive materials is another critical factor that determines the stability of OSC devices. Herein, we design and synthesize a reaction-inert rylene diimide-embedded hyperbranched polymer named as PDIEIE, which effectively reduces the work function of indium tin oxide electrode from 4.62 to 3.65 eV. Meanwhile, PDIEIE shows negligible chemical reaction with high-performance photoactive materials and no catalytic effect under strong ultraviolet illumination, resulting in much better photo-stability of OSCs with PDIEIE cathode interlayer(CIL), relative to the traditional CILs, including most-widely used metal oxides and polyethyleneimine derivatives.

Photostable lysosomal imaging of living cell with hyperspectral stimulated Raman scattering microscopy using a probe based on bisarylbutadiyne

We designed a lysosome-selective Raman probe by conjugating bisphenylbutadiyne with morpholine, a well-known lysosome targeting moiety. This probe, named Lyso-BADY, has a Raman peak 28 times more intense than that of 5-ethynyl-2'-deoxyuridine. Lysosome in living cells was successfully visualized by hyperspectral stimulated Raman scattering (SRS) microscopy with this extracellular probe. Further study showed that the Raman signal of Lyso-BADY remained steady and strong even after a prolonged irradiation time. The photo-stability feature of Lyso-BADY rendered molecules of the similar structure as potentially versatile probe for continuous imaging in the future.

Synthesis,optical properties and self-organization of blue-emitting butterfly-shaped dithienobenzosiloles

Ten novel butterfly-shaped dithienobenzosilole-based luminogens,which are peripherally installed with a variety of substituents including hydrogen,phenyl and substituted phenyl groups,have been readily prepared via an iodine-induced intramolecular electrophilic double-cyclisation reaction and subsequent deiodination or coupling reactions.The optical and electrochemical properties of these compounds were systematically investigated to clarify the relationships between their structures and properties,supported by theoretical calculations.These compounds exhibit deep-blue to sky-blue emissions and high photoluminescence quantum yields up to 0.84 in solution and solid states which are regulated by the functional blades and their steric hindrance on theα–andβ–positions of thiophene rings.Their high thermal-and photo-stabilities have been revealed and mainly attributed to the dithienobenzosilole core.