Multi-Functional Solid Additive Induced Favorable Vertical Phase Separation and Ordered Molecular Packing for Highly Efficient Layer-by-Layer Organic Solar Cells.

Layer-by-layer (LBL) deposition strategy enabling favorable vertical phase distributions has been regarded as promising candidates for constructing high-efficient organic photovoltaic (OPV) cells. However, solid additives with the merits of good stability and reproducibility have been rarely used to fine-tune the morphology of the LBL films for improved efficiency and stability. Herein, hierarchical morphology control in LBL OPV is achieved via a dual functional solid additive. Series of LBL devices are fabricated by introducing the solid additive individually or simultaneously to the donor or acceptor layer to clarify the functions of additives. Additive in the donor layer can facilitate the formation of preferable vertical component distribution, and that in the acceptor layer will enhance the molecular crystallinity for better charge transport properties. The optimized morphology ultimately contributed to high PCEs of 16.4% and 17.4% in the binary and quaternary LBL devices. This reported method provides an alternative way to controllably manipulate the morphology of LBL OPV cells.

Highly Efficient and Super Stable Full-Color Quantum Dots Light-Emitting Diodes with Solution-Processed All-Inorganic Charge Transport Layers.

High performance and super stable all-inorganic full-color quantum dot light-emitting diodes (QLEDs) are constructed by adopting solution-processed Mg-doped NiOx (Mg-NiOx ) nanoparticles as hole transport layer (HTL) and Al-doped ZnO (AZO) as electron transport layer (ETL). Mg-NiOx nanoparticles possess the advantages of low-temperature solution processability, intrinsic stability, and controllable electronic properties. UV-ozone (UVO) treatment is applied to the Mg-NiOx film to modulate its surface composition. By carefully controlling the UVO treating time, favorable energy levels can be achieved to minimize the energy barrier for hole injection. At the cathode side, Al-doping can reduce the conductivity of ZnO ETL and decrease the interface charge transfer, effectively, thus leading to more balanced charge injection and consequent high luminance and efficiency. The maximum luminance and EQE can reach as high as 38 444 cd m-2 and 5.09% for R-QLEDs, 177 825 cd m-2 and 10.1% for G-QLEDs, and 3103 cd m-2 and 2.19% for B-QLEDs. The luminance values are the highest ever reported for all-inorganic QLEDs. Furthermore, the all-inorganic devices show much better resistance to water and oxygen existing in air. The results show that the ion-doped NiOx and AZO nanoparticles would facilitate the design and development of highly efficient and super stable QLEDs.

Facile Method of Solvent-Flushing To Building Component Distribution within Photoactive Layers for High-Performance Organic Solar Cells.

Suitable donor and acceptor distribution in the blended photoactive layer benefits the charge transfer and exciton separation to boost the performance of organic solar cells (OSCs). Herein, we propose a universal solvent-flushing method for building component distribution in photoactive layers based on the different solubilities of the donor and acceptor in acetylacetone (Acac). The donor and acceptor concentration distribution through the photoactive layers is investigated by the time-of-flight secondary-ion mass spectroscopy, and the surface concentration changes are examined by contact angle measurements and atomic force microscopy tests. The charge-transfer properties of OSCs before and after Acac flushing are further investigated by the rectification ratio and light intensity-dependent Jsc and Voc measurements. For inverted OSCs based on PBDB-TF:IT-4F, the power conversion efficiency (PCE) enhances from 12.87 to 14.05%, and for a PBDB-TF:Y6-based device, the PCE also significantly increases from 15.40 to 16.51% because of greatly enhanced Jsc and FF, benefited from enhanced charge transport and suppressed charge recombination by solvent-flushing. Our findings suggest that solvent-flushing is a simply processed and easily controlled method to achieve vertical component distribution in photoactive layers to boost the performance of OSCs.

Enhancing charge transport in an organic photoactive layer via vertical component engineering for efficient perovskite/organic integrated solar cells.

Suitable vertical component distribution within an organic bulk-heterojunction (BHJ) is vital for effective exciton dissociation and smooth charge transport in perovskite/organic integrated solar cells (ISCs). Herein, a bi-continuous interpenetrating network of organic donor/acceptor materials is constructed simply by optimizing their weight ratio, and is further applied in perovskite/organic ISCs. Time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) and scanning Kelvin probe microscopy (SKPM) strongly confirm that this method can effectively restrict vertical stratification and build a desired bi-continuous framework within the organic photoactive layer, which can effectively suppress two potential recombination losses from the viewpoint of kinetics, leading to the PCE increasing from 12.63% to 15.47% for ISCs based on the structure of MAPbI3/PBDB-T : IEICO. Meanwhile, our ISCs combining a UV-vis harvesting layer of MAPbI3 and a near-infrared absorbing layer of PBDB-T : IEICO exhibit a photo-response extending to the whole visible and infrared spectrum (up to 900 nm). This work verifies that tuning the donor/acceptor weight ratio is a feasible strategy for optimizing the morphology of BHJ absorbers and suppressing charge recombination for efficient perovskite/BHJ ISCs.

All-solution-processed perovskite light-emitting diodes with all metal oxide transport layers.

All-solution-processed perovskite light-emitting diodes (PeLEDs) with all metal oxide transport layers were successfully realized based on an ITO/NiOx/CsPbBr3/ZnMgO/Al conventional device structure. A unique perovskite-polymer composite method enables the deposition of solution-processed ZnMgO nanoparticles on the perovskite film. As a result, we achieved highly efficient PeLEDs with a maximum luminance of 17 017 cd m-2, and the efficiency showed little roll-off with increasing current density.

Perfect Complementary in Absorption Spectra with Fullerene, Nonfullerene Acceptors and Medium Band Gap Donor for High-Performance Ternary Polymer Solar Cells.

Because of the mismatch between the solar irradiance spectra and the photoactive layer absorption spectra, only a part of sunlight can be utilized, which fundamentally restricting the power conversion efficiency (PCE) of the polymer solar cells (PSCs). Ternary blend PSCs, with an additional third component, have become an effective approach to extend the absorption spectra and increase the mobility of the charge carriers. Herein, we select the middle band gap PBDTBDD as an electron donor and narrow band gap ITIC and wide band gap PC60BM as electron acceptors to construct ternary blends for simultaneously enhancing the absorption intensity and expanding the absorption band. The optical properties, morphologies, and the charge-/energy-transfer behaviors of the ternary blends are investigated. By attentively adjusting the ratio of the third component, ITIC, the ternary PSCs demonstrate an expanded light-response region and greatly enhanced JSC, giving an improved overall PCE of 10.36%, much higher than that of the binary counterparts based on PBDTBDD:PC60BM (6.63%) and PBDTBDD:ITIC (9.44%). These findings indicate that proper selection of donors and acceptors to construct absorption spectra-complementary ternary blend photoactive layers is an effective way to achieve high-performance PSCs.

Finding the lost open-circuit voltage in polymer solar cells by UV-ozone treatment of the nickel acetate anode buffer layer.

Efficient polymer solar cells (PSCs) with enhanced open-circuit voltage (Voc) are fabricated by introducing solution-processed and UV-ozone (UVO)-treated nickel acetate (O-NiAc) as an anode buffer layer. According to X-ray photoelectron spectroscopy data, NiAc partially decomposed to NiOOH during the UVO treatment. NiOOH is a dipole species, which leads to an increase in the work function (as confirmed by ultraviolet photoemission spectroscopy), thus benefitting the formation of ohmic contact between the anode and photoactive layer and leading to increased Voc. In addition, the UVO treatment improves the wettability between the substrate and solvent of the active layer, which facilitates the formation of an upper photoactive layer with better morphology. Further, the O-NiAc layer can decrease the series resistance (Rs) and increase the parallel resistance (Rp) of the devices, inducing enhanced Voc in comparison with the as-prepared NiAc-buffered control devices without UVO treatment. For PSCs based on the P3HT:PCBM system, Voc increases from 0.50 to 0.60 V after the NiAc buffer layer undergoes UVO treatment. Similarly, in the P3HT:ICBA system, the Voc value of the device with a UVO-treated NiAc buffer layer increases from 0.78 to 0.88 V, showing an enhanced power conversion efficiency of 6.64%.