One-Pot Electrodeposition of Compact Layer and Mesoporous Scaffold for Perovskite Solar Cells

In this study, we report a facile method to sequentially electrodeposit a TiO₂ compact layer and a mesoporous scaffold from a single solution. This bilayer TiO₂ structure offers good controllability on the thickness and morphology by simply adjusting the depositing parameters. Currently, perovskite solar cell containing an electrodeposited TiO₂ bilayer exhibits similar power conversion efficiency when compared with the one using double spin-coating techniques, showing great potential to replace conventional tedious TiO₂ film fabrication

Crystal Growth and Dissolution of Methylammonium Lead Iodide Perovskite in Sequential Deposition: Correlation between Morphology Evolution and Photovoltaic Performance

Crystal morphology and structure are important for improving the organic–inorganic lead halide perovskite semiconductor property in optoelectronic, electronic, and photovoltaic devices. In particular, crystal growth and dissolution are two major phenomena in determining the morphology of methylammonium lead iodide perovskite in the sequential deposition method for fabricating a perovskite solar cell. In this report, the effect of immersion time in the second step, i.e., methlyammonium iodide immersion in the morphological, structural, optical, and photovoltaic evolution, is extensively investigated. Supported by experimental evidence, a five-staged, time-dependent evolution of the morphology of methylammonium lead iodide perovskite crystals is established and is well connected to the photovoltaic performance. This result is beneficial for engineering optimal time for methylammonium iodide immersion and converging the solar cell performance in the sequential deposition route. Meanwhile, our result suggests that large, well-faceted methylammonium lead iodide perovskite single crystal may be incubated by solution process. This offers a low cost route for synthesizing perovskite single crystal

Layered Double Hydroxides as an Effective Additive in Polymer Gelled Electrolyte based Dye-Sensitized Solar Cells

Layered double hydroxides (LDH), a class of anionic clay materials, were developed as an effective additive for polymer gelled electrolytes for use in dye-sensitized solar cells (DSSC). Carbonate and chloride intercalated Zn-Al LDHs, ZnAl-CO₃ LDH, and ZnAl-Cl LDH were prepared with coprecipitation methods. The addition of the two LDHs significantly improved, in terms of power conversion efficiency (PCE), over the plain poly­(vinylidene fluoride-<i>co</i>-hexafluoropropylene) (PVDF-HFP) gelled electrolyte and competed favorably with the liquid electrolyte based DSSCs, 8.13% for the liquid electrolyte, 7.48% for the plain PVDF-HFP gelled electrolyte, 8.11% for the ZnAl-CO₃ LDH/PVDF-HFP gelled electrolyte, and 8.00% for the ZnAl-Cl LDH/PVDF-HFP gelled electrolyte based DSSCs. The good performance in PCEs achieved by the LDH-loaded DSSCs came mainly from the significant boost in open circuit voltages (<i>V</i>_oc), from 0.74 V for both the liquid electrolyte and PVDF-HFP gelled electrolyte based DSSCs to 0.79 V for both the ZnAl-CO₃ LDH/PVDF-HFP and ZnAl-Cl LDH/PVDF-HFP gelled electrolyte based DSSCs. The boost in <i>V</i>_oc was contributed mainly by the positive shift in redox potential of the redox couple, I^–/I₃^–, as revealed from cyclic voltammetry analyses. As for the long-term stability, PCE retention rates of 96 and 99% after 504 h were achieved by the ZnAl-CO₃ LDH/PVDF-HFP and ZnAl-Cl LDH/PVDF-HFP gelled electrolyte based DSSCs, respectively, appreciably better than 92% achieved by the liquid electrolyte based one after 480 h

Direct Electroplated Metallization on Indium Tin Oxide Plastic Substrate

Looking foward to the future where the device becomes flexible and rollable, indium tin oxide (ITO) fabricated on the plastic substrate becomes indispensable. Metallization on the ITO plastic substrate is an essential and required process. Electroplating is a cost-effective and high-throughput metallization process; however, the poor surface coverage and interfacial adhesion between electroplated metal and ITO plastic substrate limits its applications. This paper develops a new method to directly electroplate metals having strong adhesion and uniform deposition on an ITO plastic substrate by using a combination of 3-mercaptopropyl-trimethoxysilane (MPS) self-assembled monolayers (SAMs) and a sweeping potential technique. An impedance capacitive analysis supports the proposed bridging link model for MPS SAMs at the interface between the ITO and the electrolyte

A Significant Improvement in the Electrocatalytic Stability of N‑Doped Graphene Nanosheets Used as a Counter Electrode for [Co(bpy)₃]^3+/2+ Based Porphyrin-Sensitized Solar Cells

A significant improvement in efficiency is achieved for porphyrin (YD2-o-C8) based dye-sensitized solar cells, coupled with [Co­(bpy)₃]^3+/2+ mediator electrolyte. However, the poison of the counter electrode (CE) by the [Co­(bpy)₃]^3+/2+ mediator remains a significant barrier to producing a reliable high-performance device. In this paper, nitrogen-doped graphene nanosheets (NG) are produced using a low-cost solution-based process and are used as the CE for [Co­(bpy)₃]^3+/2+ based porphyrin-sensitized solar cells. These produce significantly better electrocatalytic activity than the commonly used Pt CE. The superior performance is a result of the increased number of catalytic sites and the wettable surface that is caused by the substitution of pyridinic and pyrrolic N into the carbon-conjugated lattice. To the authors’ best knowledge, the significantly improved cycling stability (>1000 times) of NG CE for [Co­(bpy)₃]^3+/2+ redox complexes is demonstrated for the first time

A Significant Improvement in the Electrocatalytic Stability of N‑Doped Graphene Nanosheets Used as a Counter Electrode for [Co(bpy)₃]^3+/2+ Based Porphyrin-Sensitized Solar Cells

A significant improvement in efficiency is achieved for porphyrin (YD2-o-C8) based dye-sensitized solar cells, coupled with [Co­(bpy)₃]^3+/2+ mediator electrolyte. However, the poison of the counter electrode (CE) by the [Co­(bpy)₃]^3+/2+ mediator remains a significant barrier to producing a reliable high-performance device. In this paper, nitrogen-doped graphene nanosheets (NG) are produced using a low-cost solution-based process and are used as the CE for [Co­(bpy)₃]^3+/2+ based porphyrin-sensitized solar cells. These produce significantly better electrocatalytic activity than the commonly used Pt CE. The superior performance is a result of the increased number of catalytic sites and the wettable surface that is caused by the substitution of pyridinic and pyrrolic N into the carbon-conjugated lattice. To the authors’ best knowledge, the significantly improved cycling stability (>1000 times) of NG CE for [Co­(bpy)₃]^3+/2+ redox complexes is demonstrated for the first time

Structurally Simple and Easily Accessible Perylenes for Dye-Sensitized Solar Cells Applicable to Both 1 Sun and Dim-Light Environments

The need for low-cost and highly efficient dyes for dye-sensitized solar cells under both the sunlight and dim light environments is growing. We have devised <b>GJ</b>-series push–pull organic dyes which require only four synthesis steps. These dyes feature a linear molecular structure of donor–perylene–ethynylene–arylcarboxylic acid, where donor represents <i>N</i>,<i>N</i>-diarylamino group and arylcarboxylic groups represent benzoic, thienocarboxylic, 2-cyano-3-phenylacrylic, 2-cyano-3-thienoacrylic, and 4-benzo­[<i>c</i>]­[1,2,5]­thiadiazol-4-yl-benzoic groups. In this study, we demonstrated that a dye without tedious and time-consuming synthesis efforts can perform efficiently. Under the illumination of AM1.5G simulated sunlight, the benzothiadiazole-benzoic-containing <b>GJ-BP</b> dye shows the best power conversion efficiency (PCE) of 6.16% with <i>V</i>_OC of 0.70 V and <i>J</i>_SC of 11.88 mA cm^–2 using liquid iodide-based electrolyte. It also shows high performance in converting light of 6000 lx light intensity, that is, incident power of ca. 1.75 mW cm^–2, to power output of 0.28 mW cm^–2 which equals a PCE of 15.79%. Interestingly, the benzoic-containing dye <b>GJ-P</b> with a simple molecular structure has comparable performance in generating power output of 0.26 mW cm^–2 (PCE of 15.01%) under the same condition and is potentially viable toward future application

Performance Characterization of Dye-Sensitized Photovoltaics under Indoor Lighting

Indoor utilization of emerging photovoltaics is promising; however, efficiency characterization under room lighting is challenging. We report the first round-robin interlaboratory study of performance measurement for dye-sensitized photovoltaics (cells and mini-modules) and one silicon solar cell under a fluorescent dim light. Among 15 research groups, the relative deviation in power conversion efficiency (PCE) of the samples reaches an unprecedented 152%. On the basis of the comprehensive results, the gap between photometry and radiometry measurements and the response of devices to the dim illumination are identified as critical obstacles to the correct PCE. Therefore, we use an illuminometer as a prime standard with a spectroradiometer to quantify the intensity of indoor lighting and adopt the reverse-biased current–voltage (<i>I</i>–<i>V</i>) characteristics as an indicator to qualify the <i>I</i>–<i>V</i> sampling time for dye-sensitized photovoltaics. The recommendations can brighten the prospects of emerging photovoltaics for indoor applications