A micron-scale laminar MAPbBr3 single crystal for an efficient and stable perovskite solar cell.

Nowadays, obtaining a thin and large-area perovskite single-crystal (SC) is still challenging. Herein, we report a novel strategy to prepare a laminar MAPbBr3 SC with a controllable thickness of 16 µm and a size of 6 × 8 mm. Additionally, the SC solar cell achieves an intriguing efficiency of 7.11% with an impressive stability, maintaining 93% initial PCE after aging for 1000 h.

In Situ Growth of 120 cm2 CH3 NH3 PbBr3 Perovskite Crystal Film on FTO Glass for Narrowband-Photodetectors.

Organometal trihalide perovskites have been attracting intense attention due to their enthralling optoelectric characteristics. Thus far, most applications focus on polycrystalline perovskite, which however, is overshadowed by single crystal perovskite with superior properties such as low trap density, high mobility, and long carrier diffusion length. In spite of the inherent advantages and significant optoelectronic applications in solar cells and photodetectors, the fabrication of large-area laminar perovskite single crystals is challenging. In this report, an ingenious space-limited inverse temperature crystallization method is first demonstrated to the in situ synthesis of 120 cm2 large-area CH3 NH3 PbBr3 crystal film on fluorine-doped tin oxide (FTO) glass. Such CH3 NH3 PbBr3 perovskite crystal film is successfully applied to narrowband photodetectors, which enables a broad linear response range of 10-4 -102 mW cm-2 , 3 dB cutoff frequency (f 3 dB ) of ≈110 kHz, and high narrow response under low bias -1 V.

Three-dimensional TiO2/ZnO hybrid array as a heterostructured anode for efficient quantum-dot-sensitized solar cells.

The development of a novel nanoarray photoanode with a heterostructure on a transparent conducting oxide substrate provides a promising scheme to fabricate efficient energy conversion devices. Herein, we successfully synthesize the vertically aligned hierarchical TiO2 nanowire/ZnO nanorod or TiO2 nanowire/ZnO nanosheet hybrid arrays, which are proven to be excellent anode candidates for superior light utilization. Consequently, the quantum-dot-sensitized solar cells based on such hybrid arrays exhibit an impressive power conversion efficiency (PCE) under AM 1.5G one sun illumination with improved short-circuit current density (JSC) and fill factor compared to pristine TiO2 nanowire arrays. Combined with the chemical-bath-deposited Cu2S counter electrode, the eventual PCE can be further optimized to as high as 4.57% for CdS/CdSe co-sensitized quantum dot solar cells.

Achieving Highly Efficient Photoelectrochemical Water Oxidation with a TiCl4 Treated 3D Antimony-Doped SnO2 Macropore/Branched α-Fe2O3 Nanorod Heterojunction Photoanode.

Utilizing photoelectrochemical (PEC) cells to directly collecting solar energy into chemical fuels (e.g., H2 via water splitting) is a promising way to tackle the energy challenge. α-Fe2O3 has emerged as a desirable photoanode material in a PEC cell due to its wide spectrum absorption range, chemical stability, and earth abundant component. However, the short excited state lifetime, poor minority charge carrier mobility, and long light penetration depth hamper its application. Recently, the elegantly designed hierarchical macroporous composite nanomaterial has emerged as a strong candidate for photoelectrical applications. Here, a novel 3D antimony-doped SnO2 (ATO) macroporous structure is demonstrated as a transparent conducting scaffold to load 1D hematite nanorod to form a composite material for efficient PEC water splitting. An enormous enhancement in PEC performance is found in the 3D electrode compared to the controlled planar one, due to the outstanding light harvesting and charge transport. A facile and simple TiCl4 treatment further introduces the Ti doping into the hematite while simultaneously forming a passivation layer to eliminate adverse reactions. The results indicate that the structural design and nanoengineering are an effective strategy to boost the PEC performance in order to bring more potential devices into practical use.

Rational surface engineering of anatase titania core-shell nanowire arrays: full-solution processed synthesis and remarkable photovoltaic performance.

The high-performance of a well-aligned 1D nanostructured electrode relies largely on a smart and rational modification with other active nanomaterials. Herein, we present a facile solution-based route to fabricate a well-aligned metal oxide-based core-shell hybrid arrays on TCO substrate. Demonstrated samples included nanowire@nanoparticle (TNW@NP) or nanowire@nanosheet (TNW@NS) with a unique porous core/shell nanowire arrays architecture in the absence or presence of DETA during the solvothermal treatment process. The "alcoholysis" and "ripening" growth mechanism is proposed to explain the formation of honeycomb-like nanosheets shell on nanowires core. Based on careful control of experimental condition, a novel double layered TiO2 photoanode (DL-TNW@NS-YSHTSs) consisting of 16 µm thick TNW@NS under layer and 6 µm thick yolk-shell hierarchical TiO2 microspheres (YSHTSs) top layer can be obtained, exhibiting an impressive PCE over 10% at 100 mW cm(-2), which can be attributed to the well-organized photoanode composed of hierarchical core-shell arrays architecture and yolk-shell hollow spheres architecture with synergistic effects of high dye loading and superior light scattering for prominent light harvesting efficiency.

Maximizing omnidirectional light harvesting in metal oxide hyperbranched array architectures.

The scrupulous design of nanoarchitectures and smart hybridization of specific active materials are closely related to the overall photovoltaic performance of an anode electrode. Here we present a solution-based strategy for the fabrication of well-aligned metal oxide-based nanowire-nanosheet-nanorod hyperbranched arrays on transparent conducting oxide substrates. For these hyperbranched arrays, we observe a twofold increment in dye adsorption and enhanced light trapping and scattering capability compared with the pristine titanium dioxide nanowires, and thus a power conversion efficiency of 9.09% is achieved. Our growth approach presents a strategy to broaden the photoresponse and maximize the light-harvesting efficiency of arrays architectures, and may lead to applications for energy conversion and storage, catalysis, water splitting and gas sensing.

Multistack integration of three-dimensional hyperbranched anatase titania architectures for high-efficiency dye-sensitized solar cells.

An unprecedented attempt was conducted on suitably functionalized integration of three-dimensional hyperbranched titania architectures for efficient multistack photoanode, constructed via layer-by-layer assembly of hyperbranched hierarchical tree-like titania nanowires (underlayer), branched hierarchical rambutan-like titania hollow submicrometer-sized spheres (intermediate layer), and hyperbranched hierarchical urchin-like titania micrometer-sized spheres (top layer). Owing to favorable charge-collection, superior light harvesting efficiency and extended electron lifetime, the multilayered TiO2-based devices showed greater J(sc) and V(oc) than those of a conventional TiO2 nanoparticle (TNP), and an overall power conversion efficiency of 11.01% (J(sc) = 18.53 mA cm(-2); V(oc) = 827 mV and FF = 0.72) was attained, which remarkably outperformed that of a TNP-based reference cell (η = 7.62%) with a similar film thickness. Meanwhile, the facile and operable film-fabricating technique (hydrothermal and drop-casting) provides a promising scheme and great simplicity for high performance/cost ratio photovoltaic device processability in a sustainable way.

Constructing 3D branched nanowire coated macroporous metal oxide electrodes with homogeneous or heterogeneous compositions for efficient solar cells.

Light-harvesting and charge collection have attracted increasing attention in the domain of photovoltaic cells, and can be facilitated dramatically by appropriate design of a photonic nanostructure. However, the applicability of current light-harvesting photoanode materials with single component and/or morphology (such as, particles, spheres, wires, sheets) is still limited by drawbacks such as insufficient electron-hole separation and/or light-trapping. Herein, we introduce a universal method to prepare hierarchical assembly of macroporous material-nanowire coated homogenous or heterogeneous metal oxide composite electrodes (TiO2 -TiO2 , SnO2 -TiO2 , and Zn2 SnO4 -TiO2 ; homogenous refers to a material in which the nanowire and the macroporous material have the same composition, i.e. both are TiO2 . Heterogeneous refers to a material in which the nanowires and the macroporous material have different compositions). The dye-sensitized solar cell based on a TiO2 -macroporous material-TiO2 -nanowire homogenous composition electrode shows an impressive conversion efficiency of 9.51 %, which is much higher than that of pure macroporous material-based photoelectrodes to date.

Hierarchical macroporous Zn(2)SnO(4)-ZnO nanorod composite photoelectrodes for efficient CdS/CdSe quantum dot co-sensitized solar cells.

A hierarchical macroporous Zn2SnO4-ZnO nanorod composite film is prepared through a drop-casting process of PS@Zn2SnO4 and subsequent hydrothermal growth of ZnO nanorod. CdS/CdSe co-sensitized solar cells based on the macroporous Zn2SnO4-ZnO nanorod composite photoelectrode exhibits an enhancement of 34.4% in power conversion efficiency (1.68%) compared to the pristine macroporous Zn2SnO4 photoelectrode (1.25%). Especially worth noting is that the growth of ZnO nanorods contributes greatly to the enlargement of surface area and improvement of light scattering ability of the composite film, which dominates the increase of Jsc values and eventual power conversion efficiency. QDSSCs based on the optimized 9 µm thick composite photoanode film exhibits a power conversion efficiency of 2.08%, which is the highest value for the reported QDs sensitized solar cells based on the Zn2SnO4 photoelectrode.

Hydrothermal fabrication of hierarchically macroporous Zn2SnO4 for highly efficient dye-sensitized solar cells.

Hierarchical macroporous Zn(2)SnO(4) consisting of nanoparticles has been synthesized for the first time through an in situ hydrothermal and a following annealing process in the presence of a polystyrene (PS) template. Zn(2)SnO(4) macropore sizes are tuned in the range of 180-650 nm by selecting the appropriate size of PS spheres, and the building unit size of the Zn(2)SnO(4)macropore is 4.2 nm regardless of the PS sizes. The photovoltaic performances of the dye-sensitized solar cell based on hierarchical macroporous Zn(2)SnO(4) with 200, 400, 600 and 750 nm PS spheres are 5.01, 4.76, 4.39 and 3.92%, respectively. The smaller pore size of Zn(2)SnO(4) exhibits higher photovoltaic performance, which is ascribed to the higher dye loading, faster electron transport rate and slower electron recombination rate. These are confirmed by UV-vis absorption spectroscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy and electrochemical impedance spectroscopy. The double layered photoelectrode based on a Zn(2)SnO(4) nanoparticles dye adsorption layer (4.2 nm in particle size, 15 µm in film thickness) and a macroporous light scattering layer (180 nm in macropore size, 4.0 µm in thickness) shows a remarkable enhancement in power conversion efficiency (6.10%) compared to that of Zn(2)SnO(4) nanoparticles photoelectrode (5.36%) because of its superior light scattering ability.

Hierarchical oriented anatase TiO2 nanostructure arrays on flexible substrate for efficient dye-sensitized solar cells.

The vertically oriented anatase single crystalline TiO2 nanostructure arrays (TNAs) consisting of TiO2 truncated octahedrons with exposed {001} facets or hierarchical TiO2 nanotubes (HNTs) consisting of numerous nanocrystals on Ti-foil substrate were synthesized via a two-step hydrothermal growth process. The first step hydrothermal reaction of Ti foil and NaOH leads to the formation of H-titanate nanowire arrays, which is further performed the second step hydrothermal reaction to obtain the oriented anatase single crystalline TiO2 nanostructures such as TiO2 nanoarrays assembly with truncated octahedral TiO2 nanocrystals in the presence of NH4F aqueous or hierarchical TiO2 nanotubes with walls made of nanocrystals in the presence of pure water. Subsequently, these TiO2 nanostructures were utilized to produce dye-sensitized solar cells in a backside illumination pattern, yielding a significant high power conversion efficiency (PCE) of 4.66% (TNAs, J(SC) = 7.46 mA cm(-2), V(OC) = 839 mV, FF = 0.75) and 5.84% (HNTs, J(SC) = 10.02 mA cm(-2), V(OC) = 817 mV, FF = 0.72), respectively.

A double layered TiO2 photoanode consisting of hierarchical flowers and nanoparticles for high-efficiency dye-sensitized solar cells.

We report the innovative development of a double layered photoanode made of hierarchical TiO2 flowers (HTFs) as the overlayer and TiO2 nanoparticles (TNPs) as the underlayer, for dye-sensitized solar cells (DSSCs). They were prepared via a mild and simple one-step hydrothermal reaction of TiO2 nanoparticles/FTO glass substrate in an alkaline solution. The underlayer made of TNPs with a small size (20 nm in diameter) serves as a transparent photoanode for efficient dye adsorption. The overlayer consisting of HTFs (3-5 µm in diameter) embedded by TiO2 nanosheets plays multiple roles in enhancing light-scattering and fast electron transport. DSSCs based on this novel double layered photoanode (5 µm TNPs + 5 µm HTFs) exhibit greater than 7.4% power conversion efficiency (PCE), which is higher than that of single layer TNP based photoanodes (6.59%) with similar thickness (∼10 µm), and this is mainly attributed to the superior light scattering ability and fast electron transport of the former. Meanwhile, the thickness of the TNP underlayer has been optimized to further improve the PCE and an excellent PCE of over 9% has been achieved based on a 15 µm TNP + a 5 µm HTF double layered photoanode, accompanied by a short-circuit photocurrent density of 17.85 mA cm(-2), an open-circuit voltage of 763 mV and a fill factor of 0.67.

Hydrothermal fabrication of hierarchically anatase TiO2 nanowire arrays on FTO glass for dye-sensitized solar cells.

Hierarchical anatase TiO(2) nano-architecture arrays consisting of long TiO(2) nanowire trunk and numerous short TiO(2) nanorod branches on transparent conductive fluorine-doped tin oxide glass are successfully synthesized for the first time through a facile one-step hydrothermal route without any surfactant and template. Dye-sensitized solar cells based on the hierarchical anatase TiO(2) nano-architecture array photoelectrode of 18 µm in length shows a power conversion efficiency of 7.34% because of its higher specific surface area for adsorbing more dye molecules and superior light scattering capacity for boosting the light-harvesting efficiency. The present photovoltaic performance is the highest value for the reported TiO(2) nanowires array photoelectrode.