Optimization of the Ag/PCBM interface by a rhodamine interlayer to enhance the efficiency and stability of perovskite solar cells.

Effective control of the interface between the metal cathode and the electron transport layer (ETL) is critical for achieving high performance p-i-n planar heterojunction perovskite solar cells (PSCs). Several organic molecules have been explored as interlayers between the silver (Ag) electrode and the ETL for the improvement in the photovoltaic conversion efficiency (PCE) of p-i-n planar PSCs. However, the role of these organic molecules in the charge transfer at the metal/ETL interface and the chemical degradation processes of PSCs has not yet been fully understood. In this work, we systematically explore the effects of the interfacial modification of the Ag/ETL interface on PSCs using rhodamine 101 as a model molecule. By the insertion of rhodamine 101 as an interlayer between Ag and fullerene derivatives (PC60BM and PC70BM) ETLs improve the PCE as well as the stability of p-i-n planar PSCs. Atomic force microscopy (AFM) characterization reveals that rhodamine passivates the defects at the PCBM layer and reduces the band bending at the PCBM surface. In consequence, charge transfer from the PCBM towards the Ag electrode is enhanced leading to an increased fill factor (FF) resulting in a PCE up to 16.6%. Moreover, rhodamine acts as a permeation barrier hindering the penetration of moisture towards the perovskite layer as well as preventing the chemical interaction of perovskite with the Ag electrode. Interestingly, the work function of the metal cathode remains more stable due to the rhodamine incorporation. Consequently, a better alignment between the quasi-Fermi level of PCBM and the Ag work function is achieved minimizing the energy barrier for charge extraction. This work contributes to reveal the relevance of proper interfacial engineering at the metal-cathode/organic-semiconductor interface.

High Performance Metal Oxide Field-Effect Transistors with a Reverse Offset Printed Cu Source/Drain Electrode.

Nonvacuum and photolithography-free copper (Cu) films were prepared by reverse offset printing. The mechanical, morphological, structural, and chemical properties of the Cu films annealed at different temperatures were examined in detail. The Ostwald ripening-induced coalescence and grain growth in the printing Cu films were enhanced with increasing annealing temperature in N2 ambient up to 400 °C. Simultaneously, unwanted chemical impurities such as oxygen, hydrogen, and carbon in the Cu films decreased as the annealing temperature increased. The high electrical conductivity (∼6.2 µΩ·cm) of the printing Cu films annealed at 400 °C is attributed to the enlargement of the grain size and reduction of the incorporation of impurities. A printing Cu film was adopted as a source/drain (S/D) electrode in solution processable zinc tin oxide (ZTO) field-effect transistors (FETs), where the ZTO film was prepared by simple spin-coating. The ZTO FETs fabricated at a contact annealing temperature of 250 °C exhibited a promising field-effect mobility of 2.6 cm(2)/(V s), a threshold voltage of 7.0 V, and an ION/OFF modulation ratio of 2 × 10(5).

CTR9, a component of PAF complex, controls elongation block at the c-Fos locus via signal-dependent regulation of chromatin-bound NELF dissociation.

PAF complex (PAFc) is an RNA polymerase II associated factor that controls diverse steps of transcription. Although it is generally associated with actively transcribed genes, a repressive PAFc has also been suggested. Here, we report that PAFc regulates the transition from transcription initiation to transcription elongation. PAFc repressed IL-6-induced, but not TNF-α-induced, immediate early gene expression. PAFc constitutively associated with the 5'-coding region of the c-Fos locus, then transiently dissociated upon IL-6 stimulation. When CTR9, a component of PAFc, was depleted, higher levels of serine 5-phosphorylated or serine 2-phosphorylated forms of RNA Polymerase II were associated with the unstimulated c-Fos locus. We also observed an increased association of CDK9, a kinase component of the pTEF-b elongation factor, with the c-Fos locus in the CTR9-depleted condition. Furthermore, association of negative elongation factor, NELF, which is required to proceed to the elongation phase, was significantly reduced by CTR9 depletion, whereas elongation factor SPT5 recruitment was enhanced by CTR9 depletion. Finally, the chromatin association of CTR9 was specifically controlled by IL-6-induced kinase activity, because a JAK2 kinase inhibitor, AG-490, blocked its association. In conclusion, our data suggest that PAFc controls the recruitment of NELF and SPT5 to target loci in a signal- and locus-specific manner.

hCTR9, a component of Paf1 complex, participates in the transcription of interleukin 6-responsive genes through regulation of STAT3-DNA interactions.

PAF, which is composed of Paf1, Cdc73, Ctr9, Leo1, and Rtf1, is a novel complex with multiple functions in transcription-related activities. The PAF complex interacts with histone-modifying enzymes and RNA polymerase II to regulate transcription. With general transcription regulatory potential in yeast, Hyrax/Cdc73 has been reported to associate with beta-catenin to control Wnt/Wg signal-specific transcription in Drosophila. Here, we present the first evidence of IL-6 signal-specific transcriptional regulation by SH2BP1/CTR9 in mammals. Upon LPS injection of mice, we observed transient induction of the mammalian PAF complex in the liver. Inhibition of CTR9 specifically abrogated expression of IL-6-responsive genes, but had no effect on genes constitutively expressed or induced by interferon-beta, TNFalpha, or IL-1beta. The PAF complex was found in the promoter regions of IL-6-responsive HP and FGGgamma, but not in the promoter region of constitutively active GAPDH. Transcriptional activation by STAT3 was inhibited when CTR9 siRNA was introduced, whereas transcriptional activation was enhanced by mCtr9 overexpression. IL-6-activated Stat3 was found to co-localize and interact with CTR9. In CTR9-depleted cells, decreased STAT3 association with the promoter regions, as well as impaired K4-trimethylation of histone H3 in the coding regions, of target genes was observed. These data suggest that CTR9 participates in the transcription of IL-6-responsive genes through the regulation of DNA association of STAT3 and modification of histone methylation.