Molecular-Level Switching of Polymer/Nanocrystal Non-Covalent Interactions and Application in Hybrid Solar Cells

Hy brid composites obtained upon blending conjugated polymers and colloidal inorganic semiconductor nanocrystals are regarded as attractive photo-active materials for optoelectronic applications. Here we demonstrate that tailoring nanocrystal surface chemistry permits to exert control on non-covalent bonding and electronic interactions between organic and inorganic components. The pendant moieties of organic ligands at the nanocrystal surface do not merely confer colloidal stability while hindering charge separation and transport, but drastically impact morphology of hybrid composites during formation from blend solutions. The relevance of our approach to photovoltaic applications is demonstrated for composites based on poly(3-hexylthiophene) and Pbs nanocrystals, considered as inadequate before the submission of this manuscript, which enable the fabrication of hybrid solar cells displaying a power conversion efficiency that reaches 3 %. Upon (quasi)steady-state and time-resolved analisys of the photo-induced processes in the nanocomposites and their organic and inorganic components, we ascertained that electron transfer occurs at the hybrid interface yielding long-lived separated charge carriers, whereas interfacial hole transfer appears slow. Here we provide a reliable alternative aiming at gaining control over macroscopic optoelectronic properties of polymer/nanocrystal composites by acting at the molecular-level via ligands' pendant moieties, thus opening new possibilities towards efficient solution-processed hybrid solar cells

The enhancement of excitonic emission crossing Saha equilibrium in trap passivated CH3NH3PbBr3 perovskite

Metal-halide semiconductor perovskites have received great attention for the development of stable and efficient light emitting diodes and lasers, since they combine high charge carrier mobility and light emission spectral-purity with low-cost fabrication methods. Nevertheless, the role of excitons, free carries and trap states in perovskite light emission properties is still unclear due to their interdependence. In this paper we selectively manage trapping and light emission mechanisms by a reversible laser-assisted trap-passivation process performed on a CH3NH3PbBr3 perovskite layer, coupled to the inner modes of a high-quality micro-cavity, which only affects the radiative recombination. We show that photoluminescence is dominated by exciton radiative decay process and that trap states passivation increases the exciton gemination rate by reducing coulombic scattering of free electrons due to the ionized impurities. This picture provides a more general description than the model based on trap states-free Saha thermodynamic equilibrium between photo-generated species. The interdependence of free carries, trap states and excitons in the light emission properties of CH3NH3PbBr3 perovskite thin films and their relationship to device performance is a subject of debate. Here, the authors investigate the role of non-radiative recombination and demonstrate that the photoluminescence is dominated by exciton radiative decay processes

Inclusion of 2d transition metal dichalcogenides in perovskite inks and their influence on solar cell performance

Funding Information: Acknowledgments: V.N. wishes to thank the support from the ERC 3D2DPrint CoG Grant. The authors gratefully acknowledge the project Best4U—“Tecnologia per celle solari bifacciali ad alta Efficienza a 4 terminali per utility scale”. The authors are grateful to the “Progetto Tecnopolo per la Medicina di precisione, Deliberazione della Giunta Regionale n. 2117 del 21 November 2018”.Organic–inorganic hybrid perovskite materials have raised great interest in recent years due to their excellent optoelectronic properties, which promise stunning improvements in photovoltaic technologies. Moreover, two-dimensional layered materials such as graphene, its derivatives, and transition metal dichalcogenides have been extensively investigated for a wide range of electronic and optoelectronic applications and have recently shown a synergistic effect in combination with hybrid perovskite materials. Here, we report on the inclusion of liquid-phase exfoliated molybdenum disulfide nanosheets into different perovskite precursor solutions, exploring their influence on final device performance. We compared the effect of such additives upon the growth of diverse perovskites, namely CH3NH3PbI3 (MAPbI3 ) and triple-cation with mixed halides Csx (MA0.17FA0.83 )(1−x)Pb (I0.83Br0.17 )3 perovskite. We show how for the referential MAPbI3 materials the addition of the MoS2 additive leads to the formation of larger, highly crystalline grains, which result in a remarkable 15% relative improvement in power conversion efficiency. On the other hand, for the mixed cation– halide perovskite no improvements were observed, confirming that the nucleation process for the two materials is differently influenced by the presence of MoS2 .publishersversionpublishe

Polymeric nano-micelles as novel cargo-carriers for LY2157299 liver cancer cells delivery

LY2157299 (LY), which is very small molecule bringing high cancer diffusion, is a pathway antagonist against TGF\u3b2. LY dosage can be diluted by blood plasma, can be captured by immune system or it might be dissolved during digestion in gastrointestinal tract. The aim of our study is to optimize a "nano-elastic" carrier to avoid acidic pH of gastrointestinal tract, colon alkaline pH, and anti-immune recognition. Polygalacturonic acid (PgA) is not degradable in the gastrointestinal tract due to its insolubility at acidic pH. To avoid PgA solubility in the colon, we have designed its conjugation with Polyacrylic acid (PAA). PgA-PAA conjugation has enhanced their potential use for oral and injected dosage. Following these pre-requisites, novel polymeric nano-micelles derived from PgA-PAA conjugation and loading LY2157299 are developed and characterized. Efficacy, uptake and targeting against a hepatocellular carcinoma cell line (HLF) have also been demonstrated.LY2157299 (LY), which is very small molecule bringing high cancer diffusion, is a pathway antagonist against TGF\uce\ub2. LY dosage can be diluted by blood plasma, can be captured by immune system or it might be dissolved during digestion in gastrointestinal tract. The aim of our study is to optimize a \ue2\u80\u9cnano-elastic\ue2\u80\u9d carrier to avoid acidic pH of gastrointestinal tract, colon alkaline pH, and anti-immune recognition. Polygalacturonic acid (PgA) is not degradable in the gastrointestinal tract due to its insolubility at acidic pH. To avoid PgA solubility in the colon, we have designed its conjugation with Polyacrylic acid (PAA). PgA-PAA conjugation has enhanced their potential use for oral and injected dosage. Following these pre-requisites, novel polymeric nano-micelles derived from PgA-PAA conjugation and loading LY2157299 are developed and characterized. Efficacy, uptake and targeting against a hepatocellular carcinoma cell line (HLF) have also been demonstrated

Smart Windows for Building Integration: A New Architecture for Photovoltachromic Devices

A new architecture for multifunctional photoelectrochemical devices, namely photovoltachromic devices, is disclosed here, capable of producing electric energy by solar conversion also modulating the devices' optical transmittance in a smart and aesthetically sounding fashion. These devices generally consist of a titanium dioxide photoelectrode and of a bifunctional patterned counter electrode made of platinum and amorphous tungsten oxide. The innovative configuration described hereafter proposes to split the single patterned counter electrode into two distinct electrodes, physically overlapped: the central one is suitably drilled in order to allow the electrolyte to fill both communicating chambers. These three electrode devices allow three independent operating modes: photovoltaic, photoelectrochromic, and photovoltachromic. In this paper, we report the optical, electrical, and electrochemical characterization of this innovative device, varying both available catalytic surface area and the type of sensitizing dye. We eventually obtained the following conversion efficiencies, 2.75%, 2.35%, and 1.91%, in samples having different catalytic areas (397, 360, and 320 mm(2), respectively). We inferred that the higher the platinum area on the interposed platinum-poly(ethylene naphthalate)-indium tin oxide counter electrode, the higher the photovoltaic conversion efficiency. On the other hand, a decrease of the intercommunication openings generates a slowdown of bleaching processes

Full spin-coated multilayer structure hybrid light-emitting devices

We report on a multilayer structure hybrid light-emitting device (HLED) using a water/alcohol-soluble polymer poly(9,9-bis{30-[(N,N-dimethyl)-N-ethylammonium}-propyl]-2,7-fluorene dibromide) as an electron-transporting layer and a close-packed quantum dot-layer (QD-layer) as an emitting layer. The device was realized by full spin-coating technology without thermal evaporation process for the deposition of organic layers. The QD-layer was a mixture of QDs with two different sizes, in which large size QD-emitters were dispersed in small size QDs to weaken the concentration quenching. The device achieved a maximum power efficiency of 0.58 lm/W, which nearly quadrupled that of the HLED with a plain large size QD-EML. (C) 2010 American Institute of Physics.[doi: 10.1063/1.3484145

A colour tunable microcavity by weak-to-strong coupling regime transition through a light-switchable material

An organic based microcavity showing fully reversible colour tunability has been achieved for the first time. The emission output changes according to the modulation from pure photonic to polaritonic resonant modes through UV irradiation of the light-switchable matrix

Pure white hybrid light-emitting device with color rendering index higher than 90

The realization of white-light sources with a combination of high color rendering index ( CRI), which is the average of the first eight rendering indices, and the deep-red color rendering R9 is an important challenge in the field of solid-state lighting. Herein, we report on a pure white hybrid light-emitting device combining a deep-blue emission from a polymer with blue, green, and red emissions from ternary CdSe/ZnS quantum dots. By carefully designing the device structure and tuning the ratio of QDs with different sizes, high CRI of 94 and R9 of 92 at 525 cd/m(2) were achieved. (C) 2010 Optical Society of Americ

High quality factor microcavity OLED employing metal-free electrically active Bragg mirrors

A Fabry-Perot microcavity with a high quality Q-factor is an excellent tool to finely tune and narrow the emission spectrum of embedded organic dyes, leading also to a modification of the radiative emission rate (Purcell effect). For a real application of these properties in light emitting diodes and lasers, high Q-factors should be also provided in electrically-driven organic microcavities, that is still a challenge when organic materials are employed. Metallic contacts can be safely deposited onto organic layers, although they result in strong absorption losses. In this work, we successfully integrated an Organic LED architecture within specifically tailored metal-free electrically active Bragg mirrors, finely optimized to achieve simultaneously high reflectivity and good electrical properties. The resulting electroluminescent microcavity showed a Q-factor of more than 200 (emission linewidth of 2.7 nm at a peak wavelength of 555 nm) and a clear proof of the occurrence of Purcell effect leading to a decrease of exciton radiative lifetime by a factor above 6. Finally, we analysed the parameters that still limit the Q-factor of our architecture, paving the way for future improvements. The proposed approach can be exploited for the fabrication of novel monochromatic organic light sources for telecommunications or biological sensing and it represents an important step towards the realization of electrically driven organic lasers

Aryl 5-substitution of a phenyl-pyridine based ligand as a viable way to influence the opto-electronic properties of bis-cyclometalated Ir(III) heteroleptic complexes

This manuscript reports on the synthesis, the photophysical study and the electroluminescent properties of a series of heteroleptic cyclometalated iridium(III) complexes based on 2,5-diaryl-pyridines as (CN)-N-boolean AND cyclometalating ligands and acetylacetonate as ancillary ligand. The complexes were characterised by elemental analysis, ESI-MS, multinuclear NMR, TGA and electrochemistry. Their optical properties were investigated by UV-Vis and photoluminescence. DFT and TD-DFT calculations provided further insights into the effects of the 5-aryl substitution on the electronic and photophysical properties of the new complexes. The presence of suitable pi-extended ligands exerts a beneficial effect on the performances of the corresponding solution-processed light-emitting diodes, leading to a maximum brightness of 10 620 cd m(-2) at a current efficiency of 10.0 cd A(-1)