Leijing Liu

Synthesis and photovoltaic properties of novel solution-processable triphenylamine-based dendrimers with sulfonyldibenzene cores

Three conjugated dendrimers containing electron-accepting sulfonyldibenzene (SDB) cores and electron-donating triphenylamine dendrons have been synthesized through a convergent synthetic strategy without any protection/deprotection chemistry. The dendrimers were highly soluble in common organic solvents, and could form good quality optical films by spin coating. Their thermal, optical and electrical properties are manipulated by attaching different peripheral dendrons. Using these dendrimers as donors and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as acceptor, the bulk heterojunction solar cells with a structure of ITO–PEDOT–dendrimers:PCBM–LiF–Al were fabricated. The cell based on dendrimer G0 shows a relatively high power-conversion efficiency (PCE) of 0.34% under AM 1.5 illumination of 100 mW cm−2.

Magnesium‐doped Zinc Oxide as Electron Selective Contact Layers for Efficient Perovskite Solar Cells

The electron-selective contact layer (ESL) in organometal halide-based perovskite solar cells (PSCs) determines not only the power conversion efficiency (PCE) but also the thermostability of PSCs. To improve the thermostability of ZnO-based PSCs, we developed Mg-doped ZnO [Zn1-x Mgx O (ZMO)] as a high optical transmittance ESL for the methylammonium lead trihalide perovskite absorber [CH3 NH3 PbI3 ]. We further investigated the optical and electrical properties of the ESL films with Mg contents of 0-30 mol % and the corresponding devices. We achieved a maximum PCE of 16.5 % with improved thermal stability of CH3 NH3 PbI3 on ESL with the optimal ZMO (0.4 m) containing 10 mol % Mg. Moreover, this optimized ZMO PSC exhibited significantly improved durability and photostability owing to the improved chemical/photochemical stability of the wider optical bandgap ZMO.

Highly efficient and stable low-temperature processed ZnO solar cells with triple cation perovskite absorber

Although ZnO is a compatible electron transport layer (ETL) for perovskite solar cells (PSCs), the fact that MAPbI3 easily undergoes thermal decomposition on a low-temperature processed ZnO surface limits the use of one-step deposition of perovskite and hence the resulting photovoltaic performance. Herein, we demonstrate triple cation perovskite (Csx(MA0.17FA0.83)(100−x)Pb(I0.83Br0.17)3) prepared with a one-step deposition method as a stable light absorber in highly efficient PSCs with low-temperature processed ZnO as the ETL. The photovoltaic performance of the investigated PSCs was dependent on both the annealing temperature of the perovskite film and the composition of the Cs element in the perovskite structure. A remnant PbI2 passivation phase in the perovskite layer, in which the composition is Cs6(MA0.17FA0.83)94Pb(I0.83Br0.17)3 and the annealing temperature is 95 °C, leads to the highest power conversion efficiency of ∼18.9%, which is a record-high so far for low-temperature processed ZnO-based PSCs. Importantly, this PSC exhibits excellent environmental durability and photostability, which are critical characteristics for further commercialization of low-temperature processed PSCs.

Solution-processable two-dimensional conjugated organic small molecules containing triphenylamine cores for photovoltaic application

Two solution-processable two-dimensional conjugated organic small molecules based on triphenylamine (TPA) cores, TPA-BT-C8 and TPA-3Th, were designed and synthesized. As to TPA-BT-C8, two arms of the TPA core are symmetrically connected with a thiophene donor group and a benzothiadiazole acceptor group, while the third arm consists of a strong acceptor group of 2-(5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (DCM) connected through a trans double bond with the TPA core. For TPA-3Th, two arms of its TPA core are composed of only donor group, terthiophene, whereas the third arm consists of an acceptor group of cyano-n-octyl acetate connected through a trans double bond with the TPA core. The investigation indicated that TPA-BT-C8 has a lower energy band gap and wider absorption than TPA-3Th due to the strong intramolecular charge transfer effect in TPA-BT-C8. The two molecules have a deep highest occupied molecular orbital (HOMO) energy level. Bulk heterojunction photovoltaic devices were fabricated using TPA-BT-C8 or TPA-3Th as the donor and (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as the acceptor. All the devices have a high open-circuit voltage (Voc) of about 0.9 eV. Devices based on TPA-BT-C8 have a much higher short circuit current (Jsc) (8.47 mA cm−2) and power conversion efficiency (PCE) (2.26%) than devices based on TPA-3Th (4.32 mA cm−2, 1.21%), resulting from wider solar light absorption of TPA-BT-C8 and better compatibility and film-formation ability of TPA-BT-C8 with PCBM than TPA-3Th. Incident photon-to-electron conversion efficiency (IPCE) spectra also confirmed that TPA-BT-C8 based devices have a wider and red-shifted response range than TPA-3Th based devices, which leads to a higher performance of the former devices.

A theoretical study of hybrid lead iodide perovskite homologous semiconductors with 0D, 1D, 2D and 3D structures

The electrical properties, optical properties and stabilities of hybrid lead iodide perovskite homologous semiconductors with 0D, 1D, 2D and 3D structures have been investigated based on their electronic structures calculated by density functional theory (DFT). The results indicated that the power conversion efficiencies (PCEs) estimated according to the absorption spectra of 1D perovskite homologues (1.9–10.9%) and 2D perovskite homologues (4.4–6.9%) are similar. However, the charge transport properties of 1D perovskite homologues (only ∼0% of that of the reference, CH3NH3PbI3) are entirely different from those of 2D perovskite homologues (reaching 43% of that of the reference) when a polycrystalline model has been introduced, although both of them are anisotropic materials. More charge transport paths of 2D perovskite homologues have been found in the polycrystalline state, compared with those of 1D perovskite homologues. Our findings have a great realistic significance to understand the properties of polycrystalline perovskite homologues.

Biallele Expression of PEG10 Gene in Primordial Germ Cells Derived from Day 27 Porcine Fetuses

Primordial germ cells (PGCs) from day 27 porcine fetuses have often been isolated to establish pluripotent embryonic germ (EG) cell lines, but little is known regarding their imprinted gene status. In our study, we attempted to detect the imprinted gene expression of cloned embryos and EG cells derived from individual PGC of day 27 and day 35, using single nucleotide polymorphism (SNP) analysis of the paternally expression gene 10 (PEG10) as a sign of parental-origin-specific expression. The results showed biallelic gene expression of the SNP that occurred in EG cell colonies and almost all of the cloned blastocysts, demonstrating that aberrant imprinted gene expression of PEG10 occurs in the day 27 porcine PGCs, whereas monoallelic expression of the PEG10 gene occurs in all the PGC clones derived from day 35 PGCs. In addition, the same imprinted gene status was observed for blastocysts derived from both male and female PGCs, indicating that the parental genomic imprinting is erased in male and female germlines.

Influence of hole transport layers on internal absorption, charge recombination and collection in HC(NH2)2PbI3 perovskite solar cells

A comprehensive study of the internal absorption, charge recombination and collection in HC(NH2)2PbI3 (FAPbI3) perovskite solar cells (PeSCs) with poly(3-hexylthiophene-2,5-diyl) (P3HT) and 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amino)-9,9′-spirobifluorene (spiro-OMeTAD) as the hole transport layers (HTLs) is presented. The optical simulation shows that the optical-field distribution and internal absorption of the perovskite layer are different in the cavity region for wavelength > 500 nm in PeSCs with HTLs of P3HT and spiro-OMeTAD. The transient photo-current (TPC) and photoinduced charge extraction by linearly increasing voltage (photo-CELIV) investigations reveal that the charge recombination in PeSCs is much better restrained by using spiro-OMeTAD as the HTL. The light intensity dependent J–V performance indicates that spiro-OMeTAD is more favorable for efficient charge collection due to its suppressed charge recombination. These results manifest that the HTL can affect the internal absorption of the perovskite layer, and the spiro-OMeTAD HTL is beneficial for reducing the recombination and enhancing the charge collection in PeSCs.

Silica nanoparticles based on an AIE-active molecule for ratiometric detection of RNS in vitro

Nitric oxide (NO), known as a reactive nitrogen species (RNS), has been considered to be a significant factor in many cell-related biological processes. There is a great desire to develop fluorescent probes that can highly sensitively and selectively detect NO in living cells. Herein, a fluorescent probe, a tetraphenylethene (TPE) derivative TPE-2NH2, with aggregation induced emission (AIE) properties was designed and synthesized. Then silica nanoparticles based on TPE-2NH2 were fabricated for ratiometric detection of NO in vitro with high sensitivity and selectivity. In the presence of NO, the fluorescence of the silica nanoparticles changes from 519 nm (green) to 655 nm (red) because of the chemical reaction between NO and o-phenylenediamine in TPE-2NH2. The silica nanoparticles exhibited very high sensitivity and selectivity towards NO in aqueous buffer, and the response time was as short as 5 minutes. Moreover, the silica nanoparticles can also highly sensitively and selectively respond to NO produced in living cells. When MCF-7 cancer cells were activated by lipopolysaccharides (LPS), which can effectively induce the production of NO, the red emission signal of the silica nanoparticles obviously increased. This demonstrated that the silica nanoparticles showed fine imaging contrast towards NO in MCF-7 cancer cells, which provides a facile tool to detect intracellular NO.

Chloride treatment for highly efficient aqueous-processed CdTe nanocrystal-based hybrid solar cells

This work presents the influence of chloride treatment on the photovoltaic performance, microstructure, charge carrier dynamics, and surface chemical composition of aqueous-processed CdTe nanocrystal (NC)-based hybrid solar cells (HSCs). By applying CdCl2 treatment on the CdTe films through a spin-coating method, the power conversion efficiency (PCE) of the HSCs is largely improved from 4.49% to 6.01%. We show that the main role of chloride treatment is to promote the grain growth of the CdTe NCs, which leads to an increase in charge carrier lifetime. It is also demonstrated that CdCl2 treatment can prevent the generation of detrimental surface oxides and improve the wettability of the CdTe films.

Label-Free Aptamer-Based Biosensor for Specific Detection of Chloramphenicol Using AIE Probe and Graphene Oxide

A facile, sensitive, and label-free aptamer-based fluorescent biosensor (aptasensor) for chloramphenicol (CAP) detection was successfully developed based on an aggregation-induced emission (AIE) probe and graphene oxide (GO). In this aptasensor, the specific aptamer of CAP (C-Apt) is used as the recognition part, an AIE molecule, 9,10-distyrylanthracene (DSA) derivative with short alkyl chains (9,10-bis{4-[2-(N,N,N-trimethylammonium)-ethoxy]styrene}anthracene dibromide, DSAC2N), as the fluorescent probe, and GO with a low oxidation degree as the fluorescent quencher. Initially, the AIE probe DSAC2N and C-Apt could be adsorbed on GO through π-stacking interactions, and the fluorescence of DSAC2N could be efficiently quenched due to the energy transfer between DSAC2N and GO. When CAP is added, C-Apt can preferentially bind with CAP and the newly formed complex (C-Apt–CAP) can be released from GO, resulting in the recovery of the fluorescence signal of DSAC2N. Thus, with the aid of GO, turn-on detection of CAP can be readily realized by monitoring the fluorescence signal of DSAC2N from “off” to “on”. Under the optimized conditions, the aptasensor exhibits a high sensitivity toward CAP with a limit of detection of 1.26 pg/mL. Besides, we have successfully applied this aptasensor to the detection of CAP in spiked milk.