Tonggang Jiu

Highly Efficient Electron Transport Obtained by Doping PCBM with Graphdiyne in Planar-Heterojunction Perovskite Solar Cells

Organic-inorganic perovskite solar cells have recently emerged at the forefront of photovoltaics research. Here, for the first time, graphdiyne (GD), a novel two dimension carbon material, is doped into PCBM layer of perovskite solar cell with an inverted structure (ITO/PEDOT:PSS/CH3NH3PbI(3-x)Cl(x)/PCBM:GD/C60/Al) to improve the electron transport. The optimized PCE of 14.8% was achieved. Also, an average power conversion efficiency (PCE) of PCBM:GD-based devices was observed with 28.7% enhancement (13.9% vs 10.8%) compared to that of pure PCBM-based ones. According to scanning electron microscopy, conductive atomic force microscopy, space charge limited current, and photoluminescence quenching measurements, the enhanced current density and fill factor of PCBM:GD-based devices were ascribed to the better coverage on the perovskite layer, improved electrical conductivity, strong electron mobility, and efficient charge extraction. Small hysteresis and stable power output under working condition (14.4%) have also been demonstrated for PCBM:GD based devices. The enhanced device performances indicated the improvement of film conductivity and interfacial coverage based on GD doping which brought the high PCE of the devices and the data repeatability. In this work, GD demonstrates its great potential for applications in photovoltaic field owing to its networks with delocalized π-systems and unique conductivity advantage.

A Small‐Molecule Zwitterionic Electrolyte without a π‐Delocalized Unit as a Charge‐Injection Layer for High‐Performance PLEDs

Small-molecule zwitterionic materials were found to be more efficient as charge-injection materials in an organic electronic device than a previously described polymer (see structures). Furthermore, the superior device performance observed for 1 indicates that it is not necessary to focus only on π-delocalized systems and that solid ionic liquids may be promising alternative candidates for charge-injection materials.

Polyelectrolyte based hole-transporting materials for high performance solution processed planar perovskite solar cells

Using polyelectrolytes (P3CT-Na) as hole-transporting materials (HTMs), high performance inverted perovskite solar cells with a PCE of 16.6% could be obtained, which was more than 20% improvement compared with those based on the PEDOT:PSS HTM (PCE of 13.7%). The performance improvement can be ascribed to the desirable match of energy levels as well as the better crystalline properties and larger grain size of CH3NH3PbCl3−xIx films on P3CT-Na. Importantly, rather good performance with PCE over 11% is achievable even if the P3CT-Na thickness ranges from 1 nm to 52 nm. Our work indicated the promising applications of polyelectrolyte based HTMs in perovskite solar cells and may provide some insights into the design and synthesis of new HTMs to further improve the device performance.

Solution-Processed Hybrid Cathode Interlayer for Inverted Organic Solar Cells

A novel hybrid material CdS/2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (CdS·BCP) was prepared from the decomposition of its organic soluble precursor complex Cd(S2COEt)2·(BCP) by low-temperature treatment. CdS·BCP, which integrated the favorable properties of solvent durability, and high electron mobility of CdS as well as the good hole blocking property of BCP, was designed and developed as the interface modification material to improve electron collection in bulk heterojunction organic solar cells (OSCs). The inverted OSCs with CdS·BCP as buffer layer on ITO showed improved efficiency compared with the pure CdS or BCP. Devices with CdS·BCP as interlayer exhibited excellent stability, only 14.19% decay of power conversion efficiencies (PCEs) was observed (from 7.47% to 6.41%) after stored in glovebox for 3264 h (136 days). Our results demonstrate promising potentials of hybrid materials as the interface modification layers in OSCs, and provide new insights for the development of new interface modification materials in the future.

Improving Efficiency by Hybrid TiO2 Nanorods with 1,10-Phenanthroline as A Cathode Buffer Layer for Inverted Organic Solar Cells

We reported a significant improvement in the efficiency of organic solar cells by introducing hybrid TiO2:1,10-phenanthroline as a cathode buffer layer. The devices based on polymer thieno[3,4-b]thiophene/benzodithiophene:[6,6]-phenyl C71-butyric acid methyl ester (PTB7:PC71BM) with hybrid buffer layer exhibited an average power conversion efficiency (PCE) as high as 8.02%, accounting for 20.8% enhancement compared with the TiO2 based devices. The cathode modification function of this hybrid material could also be extended to the poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) system. We anticipate that this study will stimulate further research on hybrid materials to achieve more efficient charge collection and device performance.

Manipulating surface ligands of copper sulfide nanocrystals: synthesis, characterization, and application to organic solar cells.

CuS NCs were synthesized via a facile sol-gel method without post-thermal treatment. The as-prepared CuS NCs were analyzed and confirmed by XRD, HR-TEM, EDS and XPS as hexagonal covellite CuS. The average diameter of the samples was about 3nm with narrow size distribution. CuS NCs can form a thin and smooth film without ligand-exchange that can be used as hole transport layer in organic solar cell. These hydrophilic CuS NCs with pyridine ligands can be exchanged with OAm and OA rapidly at room temperature and present hydrophobic characteristic, resulting in forming oil-soluble CuS NCs. This makes it possible tuning the surface property of CuS NCs and has the potential application for different fields.

Synthesis of Chlorine-Substituted Graphdiyne and Applications for Lithium-Ion Storage

Chlorine-substituted graphdiyne (Cl-GDY) is prepared through a Glaser-Hay coupling reaction on the copper foil. Cl-GDY is endowed with a unique π-conjugated carbon skeleton with expanded pore size in two dimensions, having graphdiyne-like sp- and sp2 - hybridized carbon atoms. As a result, the transfer tunnels for lithium (Li) ions in the perpendicular direction of the molecular plane are enlarged. Moreover, benefiting from the bottom-to-up fabrication procedure of graphdiyne and the strong chemical tailorability of the alkinyl-contained monomer, the amount of substitutional chlorine atoms with appropriate electronegativity and atom size is high and evenly distributed on the as-prepared carbon framework, which will synergistically stabilize the Li intercalated in the Cl-GDY framework, and thus generate more Li storage sites. Profiting from the above unique structure, Cl-GDY shows remarkable electrochemical properties in lithium ion half-cells.

Solvents Induced ZnO Nanoparticles Aggregation Associated with Their Interfacial Effect on Organic Solar Cells

ZnO nanofilm as a cathode buffer layer has surface defects due to the aggregations of ZnO nanoparticles, leading to poor device performance of organic solar cells. In this paper, we report the ZnO nanoparticles aggregations in solution can be controlled by adjusting the solvents ratios (chloroform vs methanol). These aggregations could influence the morphology of ZnO film. Therefore, compact and homogeneous ZnO film can be obtained to help achieve a preferable power conversion efficiency of 8.54% in inverted organic solar cells. This improvement is attributed to the decreased leakage current and the increased electron-collecting efficiency as well as the improved interface contact with the active layer. In addition, we find the enhanced maximum exciton generation rate and exciton dissociation probability lead to the improvement of device performance due to the preferable ZnO dispersion. Compared to other methods of ZnO nanofilm fabrication, it is the more convenient, moderate, and effective to get a preferable ZnO buffer layer for high-efficiency organic solar cells.

High-Performance Inverted Solar Cells Based on Blend Films of ZnO Naoparticles and TiO2 Nanorods as a Cathode Buffer Layer

We reported the favorable cathode buffer layer based on a blend of ZnO nanoparticles (NPs) and TiO2 nanorods (NRs) applied to inverted solar cells. In addition to the high optical transmittance, the resultant blend film gave a relatively dense film with lower roughness than that of the respective single-component film. This improved the interface contact between the buffer layer and photoactive layer and therefore reduced the contact resistance and leakage current. Moreover, the combination of NRs and NPs increased the efficiency of electron transport and collection by providing both a direct path for electron transport from TiO2 NRs and a large contact area between ZnO NPs and the active layer. Consequently, both the short-circuit current density (Jsc) and fill factor (FF) in the device were improved, leading to an improvement of the device performance. The best power conversion efficiency (PCE) based on the blend film as the buffer layer reached 8.82%, which was preferable to those of a single ZnO NP film (7.76%) and a TiO2 NR-based device (7.66%).

Highly Efficient Organic Photovoltaics via Incorporation of Solution-Processed Cesium Stearate as the Cathode Interfacial Layer

Highly efficient organic solar cells were successfully demonstrated by incorporating a solution-processed cesium stearate between the photoactive layer and metal cathode as a novel cathode interfacial layer. The analysis of surface potential change indicated the existence of an interfacial dipole between the photoactive layer and metal electrode, which was responsible for the power conversion efficiency (PCE) enhancement of devices. The significant improvement in the device performance and the simple preparation method by solution processing suggested a promising and practical pathway to improve the efficiency of the organic solar cells.