Ion-Exchange Polymer Network Enhanced Interfacial Compatibility for Stable and Efficient Inverted Perovskite Solar Cells.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a low-cost and water-processable hole transport material has been widely used in various optoelectronic devices. Although the incorporation of anionic polyelectrolyte PSS in PEDOT contributes to superior water solubility, the trade-off between efficiency and stability remains a challenging issue, limiting its reliable application in perovskite solar cells (PSCs). Herein, we proposed an ion-exchange (IE) strategy to effectively control the doping degree, interfacial charge dynamics, and reliability of PEDOT:PSS in PSCs. This IE approach based on hard cation-soft anion rules enabled effective anion exchange between PEDOT:PSS and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), which favored enhancing the film conductivity, regulating the perovskite crystallization, and reducing the carrier losses at the interfaces. Consequently, a notable increase of the open-circuit voltage from 0.88 to 1.02 V was realized, resulting in a champion efficiency of 18.7% compared to the control (15.4%) in inverted PSCs. More encouragingly, this IE strategy significantly promoted the thermal and environmental stability of unsealed devices by maintaining over 80% of initial efficiencies after 2000 h. This work provides an effective way to regulate the doping state of the PEDOT-based hole transport material and guides the development of robust polymeric conducting materials for efficient perovskite photovoltaics.

Sequential Molecule-Doped Hole Conductor to Achieve >23% Perovskite Solar Cells with 3000-Hour Operational Stability.

Although hole transport layers (HTLs) based on solution-processed doped Spiro-OMeTAD are extremely popular and effective for their remarkable performance in n-i-p perovskite solar cells (PSCs), their scalable application is still being held back by poor chemical stability and unsatisfied scalability. Essentially, the volatile components and hygroscopic nature of ionic salts often cause morphological deformation that deteriorate both device efficiency and stability. Herein, a simple and effective molecular implantation-assisted sequential doping (MISD) approach is strategically introduced to modulate spatial doping uniformity of organic films and fabricate all evaporated Spiro-OMeTAD layer in which phase-segregation free HTL is achieved accompanied with high molecular density, uniform doping composition, and superior optoelectronic characteristics. The resultant MISD-based devices attain a record power conversion efficiency (PCE) of 23.4%, which represents the highest reported value among all the PSCs with evaporated HTLs. Simultaneously, the unencapsulated devices realize considerably enhanced stability by maintaining over 90% of their initial PCEs in the air for 5200 h and after working at maximum power point under illumination for 3000 h. This method provides a facile way to fabricate robust and reliable HTLs toward developing efficient and stable perovskite solar cells.

Isolation and structural characterization of two very large, and largely empty, endohedral fullerenes: Tm@C(3v)-C(94) and Ca@C(3v)-C(94).

The structures of two newly synthesized endohedral fullerenes, Tm@C(3v)-C(94) and Ca@C(3v)-C(94), have been determined by single crystal X-ray diffraction on samples cocrystallized with Ni(II)(octaethylporphyrin). Both compounds exhibit the same cage geometry and conform to the isolated pentagon rule (IPR). The metal ions within these rather large cages are localized near one end and along the C(3) axis. While the calcium ion is situated over a C-C bond at a 6:6 ring junction, the thulium ion is positioned above a six-membered ring of the fullerene.

Detection of a family of gadolinium-containing endohedral fullerenes and the isolation and crystallographic characterization of one member as a metal-carbide encapsulated inside a large fullerene cage.

A series of di-gadolinium endohedrals that extends from Gd(2)C(90) to Gd(2)C(124) has been detected by mass spectrometry of the o-dichlorobenzene extract of the carbon soot produced by direct current arcing of graphite rods filled with a mixture of Gd(2)O(3) and graphite powder. Chromatographic separation has led to the isolation of pure samples of two isomers of Gd(2)C(94) and the complete series from Gd(2)C(96) to Gd(2)C(106). Endohedral fullerenes of the type M(2)C(2n) can exist as the conventional endohedral, M(2)@C(2n), or as the carbide-containing endohedral, M(2)C(2)@C(2n-2). Crystallographic characterization of the more rapidly eluting isomer of Gd(2)C(94) reveals that it possesses the carbide structure, Gd(2)C(2)@D(3)(85)-C(92). Computational studies suggest that the more slowly eluting isomer of Gd(2)C(94) may be a conventional endohedral, Gd(2)@C(2)(121)-C(94).

Molecular simulation of adsorption and separation of mixtures of short linear alkanes in pillared layered materials at ambient temperature.

Grand canonical Monte Carlo and configurational-bias Monte Carlo techniques are carried out to simulate the adsorption of ternary and quaternary mixtures of short linear alkanes, involving methane, ethane, propane, and n-butane, in pillared layered materials at ambient temperature, T=300 K. In the simulation, a pillared layered pore is modeled by a uniform distribution of pillars between two layered walls built by making two separate talc lamellas parallel each other with a given size of interlayer distance. The interaction between fluid molecules and two layered walls is measured by storing potentials calculated in advance at a series of grid points. The interaction between fluid molecules and pillars is also calculated by a site-to-site method. The potential model proposed in this work is proved to be effective because of the simulation result being good agreement with the experimental data for the adsorption of nitrogen at 77 K. Then, the adsorption isotherms of mixtures of short linear alkanes in pillared layered pores with three different porosities psi=0.98, 0.93 and 0.85, and three pore widths H=1.02, 1.70 and 2.38 nm at 300 K are obtained by taking advantage of the model. The simulation results tell us that the longer chain component is preferentially adsorbed at low pressures, and its adsorption increases and then decreases as the pressure increases while the shorter chain component is still adsorbed at high pressures. Moreover, the sorption selectivity of pillared layered materials for the longest chain component in alkane mixtures increases as the mole fraction of methane in the gas phase increases. The selectivity of pillared layered materials for the longest chain component in alkane mixtures also increases as the pore width decreases and the porosity increases.