The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201901673.Low-dimensional Ruddlesden-Popper perovskites (RPPs) exhibit excellent stability in comparison with 3D perovskites; however, the relatively low power conversion efficiency (PCE) limits their future application. In this work, a new fluorine-substituted phenylethlammonium (PEA) cation is developed as a spacer to fabricate quasi-2D (4FPEA) 2 (MA) 4 Pb 5 I 16 (n = 5) perovskite solar cells. The champion device exhibits a remarkable PCE of 17.3% with a J sc of 19.00 mA cm −2 , a V oc of 1.16 V, and a fill factor (FF) of 79%, which are among the best results for low-dimensional RPP solar cells (n ≤ 5). The enhanced device performance can be attributed as follows: first, the strong dipole field induced by the 4-fluoro-phenethylammonium (4FPEA) organic spacer facilitates charge dissociation. Second, fluorinated RPP crystals preferentially grow along the vertical direction, and form a phase distribution with the increasing n number from bottom to the top surface, resulting in efficient charge transport. Third, 4FPEA-based RPP films exhibit higher film crystallinity, enlarged grain size, and reduced trap-state density. Lastly, the unsealed fluorinated RPP devices demonstrate superior humidity and thermal stability. Therefore, the fluorination of the long-chain organic cations provides a feasible approach for simultaneously improving the efficiency and stability of low-dimensional RPP solar cells. Perovskite Solar CellsOrganic-inorganic hybrid perovskites have attracted tremendous attention due to their high absorption coefficients, [1] high charge carrier mobility, [2] high defect tolerance, [3] and long diffusion lengths. [4] Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached 23.32% in the past few years, the intrinsic material instability of 3D perovskites still remain unresolved, which hinder the future commercialization of perovskite solar cells. [5] Compared

This brief review summarizes non-fullerene acceptors based on perylene diimides used in bulk-heterojunction solar cells which were reported mainly during 2014–2016.

Substituting the hydrogen atoms on the conjugated side chain of a wide-bandgap polymer J52 with chlorine atoms can simultaneously increase the J sc , V oc , and FF of nonfullerene OSCs, leading to an efficiency boost from 3.78 to 11.53%, which is among the highest efficiencies for as-cast OSCs reported to date. To illustrate the impressive 3-fold PCE enhancement, the chlorination effect on the optical properties and energy levels of polymers, film morphology, and underlying charge dynamics is systematically investigated. Grazing incidence wide-angle X-ray scattering studies show that chlorinated J52-2Cl exhibits strong molecule aggregation, the preferred face-on orientation, and enhanced intermolecular π−π interactions, hence increasing the charge carrier mobility by 1 order of magnitude. Moreover, chlorination modifies the miscibility between the donor and acceptor and consequently optimizes the phase separation morphology of J52-2Cl:ITIC blend films. These results highlight chlorination as a promising approach to achieve highly efficient as-cast OSCs without any extra treatment.

No abstract

The incorporation of one 3,4-ethylenedioxythiophene (EDOT) building block into a diketopyrrolopyrrole (DPP) based D–A conjugated polymer could facilitate the p-doping of a D–A conjugated polymer and improve thermoelectric performance.

No abstract

The geometries of acceptors based on perylene diimides (PDIs) are important for improving the phase separation and charge transport in organic solar cells. To fine-tune the geometry, biphenyl, spiro-bifluorene, and benzene were used as the core moiety to construct quasi-three-dimensional nonfullerene acceptors based on PDI building blocks. The molecular geometries, energy levels, optical properties, photovoltaic properties, and exciton kinetics were systematically studied. The structure-performance relationship was discussed as well. Owing to the finest phase separation, the highest charge mobility and smallest nongeminate recombination, the power conversion efficiency of nonfullerene solar cells using PDI derivatives with biphenyl core (BP-PDI) as acceptor reached 7.3% when high-performance wide band gap donor material poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] was blended.

No abstract