Solar cells incorporating lead halide-based perovskite absorbers can exhibit impressive power conversion efficiencies (PCEs), recently surpassing 15%. Despite rapid developments, achieving precise control over the morphologies of the perovskite films (minimizing pore formation) and enhanced stability and reproducibility of the devices remain challenging, both of which are necessary for further advancements. Here we demonstrate vacuum-assisted thermal annealing as an effective means for controlling the composition and morphology of the CH(3)NH(3)PbI(3) films formed from the precursors of PbCl(2) and CH(3)NH(3)I. We identify the critical role played by the byproduct of CH(3)NH(3)Cl on the formation and the photovoltaic performance of the perovskite film. By completely removing the byproduct through our vacuum-assisted thermal annealing approach, we are able to produce pure, pore-free planar CH(3)NH(3)PbI(3) films with high PCE reaching 14.5% in solar cell device. Importantly, the removal of CH(3)NH(3)Cl significantly improves the device stability and reproducibility with a standard deviation of only 0.92% in PCE as well as strongly reducing the photocurrent hysteresis.

COMMUNICATION 1203 wileyonlinelibrary.com www.MaterialsViews.com www.advenergymat.dePolymer solar cells hold the promise for a cost-effective, lightweight solar energy conversion platform, which can benefi t from simple solution processing of the active layer. [1][2][3] At present, bulk hetero-junction polymer solar cells show power conversion effi ciency (PCE) close to or over than 8%. [4][5][6][7][8][9][10] However, the quantum effi ciency of polymer solar cells is mainly limited due to the comparatively low carrier mobility and charge recombination. [1][2][3] A thinner active layer can lower the probability of charge recombination and increase the carrier drift velocity by having higher electric fi eld, thus enhancing the internal quantum effi ciency, while a minimum fi lm thickness is always required to ensure suffi cient photon absorption. [ 11 , 12 ] Therefore, how to increase the light absorption of a polymer fi lm at a limited thickness of fi lm still remains as a challenge. The incorporation of plasmonic structures with photovoltaic devices has been shown to increase solar cell photo-current and may lead to new opportunities for inexpensive, and high effi ciency solar cell designs. [13][14][15][16][17][18][19][20] Recently, metallic nanostructures have been introduced into thin inorganic semiconductor solar cells (e.g. Si and GaAs solar cells) for highly effi cient light harvesting by strong light scattering behavior and concentrated near fi eld through the localized and surface plasmonic effects of different metallic nanostructures. [12][13][14][15][16][17] More recently, metallic nanostructures have been used to enhance the performance of bulk heterojunction polymer solar cells, such as introducing the localized plasmonic nanostructure of metallic nanoparticles (NPs) in carrier transport layer, [18][19][20][21][22] incorporate into active layer of bulk junctions, [23][24][25] both carrier transport layer and active layer [ 26 ] and most of them are concentrated on wide band-gap polymer, such as poly-3(hexylthiophene) (P3HT). Importantly, low bandgap polymer can cover a broad absorption range, it is therefore attractive if we can enhance the PCE of low bandgap polymer solar cell by plasmonic structure. In this study, the low bandgap polymer benzodithiophene polymers (PTB7) [ 6 ] is used to demonstrate the surface plasmonic effects of large-area metallic grating on patterned active layer. By patterning the active layer via a simple imprinting technique [ 26 -29 ] and coating metal oxide/ Ag, grating electrode is introduced to enhance optical properties of polymer solar cells. For a strict comparison, we fi rstly optimize the unpatterned polymer solar cell structures. About 10% of short current density improvement is obtained, and PCE achieves 7.73% for the plasmonic inverted solar cells with the low-bandgap polymer as the active layer. An observable improvement in PCE is mainly ascribed by the surface plasmonic and scattering effects due to the Ag grating.To demonstrate surface plasmonic effects in low...

Chloride (from PbCl 2 or CH 3 NH 3 Cl) has been reported to improve the morphology of perovskite thin film and power conversion efficiency (PCE) of corresponding perovskite solar cells (PSCs). However, the mechanism why chloride functions well in perovskite is unclear. In this work, we investigate the effects of chloric additive (from CH 3 NH 3 Cl) on the morphology, diffusion length, and trap state of perovskite thin film, as well as the PCE of PSC. We find that the chloric additive can significantly increase the hole and electron diffusion length and also reduce the bulk trap-state density in perovskite thin film, which is considered to be the main reason for improving the performance of PSC. These results contribute to better understanding of the function of chloride in perovskite and suggest room to further improve the PCE of PSC via decreasing the trap state in perovskite film.

Until now, the selective (hetero)­aryl C–H alkylation without the assistance of directing groups or preinstallation of functionalities still remains a highly challenging goal. Herein, by developing acid-resistant multispherical cavity carbon-supported cobalt oxide nanocatalysts (CoO x /MSCC) and a hydrogen transfer-mediated activation mode for nonactivated N-heteroaromatics, we present a direct reductive quinolyl and isoquinolyl β-C–H alkylation with various aldehydes as the alkylating agents. The catalytic transformation features broad substrate scope, good functional tolerance, use of Earth-abundant and reusable cobalt catalysts, and no need for prefunctionalizations, demonstrating that the developed nanocatalysts enable one to directly functionalize inert N-heteroaryl systems that are difficult to realize by organometallic complexes.

The combination of metal ions with malic acid (hydroxybutane diacid) and 4,4‘-bipyridine ligands under hydro(solvo)thermal conditions has resulted in the formation of three novel coordination polymers, {[M(C4H4O5)(bipy)0.5]·H2O} n (M = CoII (1), NiII (2), 0.3CoII + 0.7NiII (3); C4H4O5 2- = malate dianion, bipy = 4,4‘-bipyridine). The metal ions were interconnected by α- and β-carboxylates of malate to produce infinite [M(C4H4O5)] n layers, which were further pillared by bridging bipy molecules to form a 3D network. The μ3-malate ligand exhibits a pentadentate coordination mode, with all of the five oxygen atoms participating in the coordination. The magnetic pathways of three compounds are through M−O−C−O−M with nonplanar skew-skew conformations; compound 1 shows antiferromagnetic interactions, while 2 is ferromagnetic, due to different electronic configurations of the metal ions.