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Although the best research-cell efficiency (>25%) of perovskite solar cells (PSCs) is comparable with that of silicon solar cells, the industrial application of PSCs is limited by the further improvement of performance and stability. Here, cesium acetate (CsAc) is introduced into lead iodide (PbI2) precursor, which tunes the morphology and structure of PbI2 and promotes the conversion of PbI2 into stable large perovskite grains. Moreover, the introduction of Cs+ and Ac− can fill up the FA+, I− vacancy and combine with uncoordinated Pb2+, which reduces the trap density. The CsAc introduction not only optimizes the quality of perovskite films, but also reduces the defects in the bulk phase, which facilitates the transportation of carriers and mitigates non-radiative recombination. Consequently, the CsAc optimized PSCs achieve a maximum power conversion efficiency (PCE) of 22.01%. Meanwhile, the unsealed device still maintains an initial PCE of 96% after being exposed in the air for 45 days.

Transition metal phosphates have aroused wide attention and been applied in the field of energy conversion due to their high catalytic properties and low cost, but magnetic metal phosphates are rarely used in DSSC. In this work, the magnetic CoP@FeP4 thin film was prepared on carbon paper (CP) using a two-step process and proposed as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). The morphology of CoP@FeP4@CP with a silkworm-like structure is advantageous to enhance the catalytic ability for the interface reaction, establish a good connection between the electrode material and electrolyte, and accelerate the electron transmission. The characterizations using cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel curves all indicate that the CoP@FeP4@CP CE shows excellent electrochemical catalytic performance for the I−/I3− electrolyte. Under optimal conditions, a high power conversion efficiency of 9.88% is achieved for DSSC with CoP@FeP4@CP CE much higher than that of Pt (7.49%) and CoP@CP (8.73%) CEs. This phenomenon can be attributed to the unique chemical structure and the synergistic effect of CoP@FeP4@CP CE. CoP@FeP4@CP CE with the advantages of efficient, low cost, and facile synthesis is a promising alternative to the expensive Pt CE for the DSSCs in the future.

In this study, a metal-organic gels (MOGs)-coated solid-phase microextraction (SPME) fiber was developed and coupled with gas chromatography-mass spectrometer (GC–MS) for highly sensitive detection of pesticide residues in fruit samples. The MOGs-coated fiber was prepared using a simple in situ hydrothermal growth method, and the influencing factors in preparation process were investigated in detail. The prepared fiber showed high extraction efficiency, and excellent acid and alkali resistance. Under the optimized conditions, the developed SPME-GC–MS method showed wide linearity in the range of 0.01–10.00 ng mL−1 for eleven pesticides. The limits of detection (LODs, S/N=3) and quantification (LOQs, S/N = 10) were in the range of 0.001–0.052 ng mL−1 and 0.005 -0.094 ng mL−1, respectively. The relative standard deviations (RSDs, n = 5) of single steel wire and steel wire to steel wire were all below 10.7%. The method was successfully applied to determine pesticide residues in fruit samples with satisfactory recovery of 79.3% -117.7% and RSDs varying from 2.9% to 9.6%. The MOGs-coated fiber stayed stable after 100 times extractions without significant changes in extraction capacity. The results indicated that the MOGs provided a promising coating for SPME of pesticide residues in complicated matrix.

The quality of the perovskite layer has an important influence on the photovoltaic performance and stability of perovskite solar cells. An appropriate additive can effectively improve the quality of perovskites. In this work, pyrrole is introduced into a cesium-containing triple cation perovskite precursor solution and this strategy is demonstrated to control the crystallinity of perovskite films. The pyrrole ring is hydrophobic, and its nitrogen atom (N) can combine with the lead–iodine (Pb–I) framework by coordinating with Pb ions or pyrrole forms hydrogen bonds with organic cations. XRD patterns and AFM images prove that pyrrole significantly affects the crystallinity and roughness of perovskite films. The pyrrole-modified device exhibits a champion power conversion efficiency of 20.07%, while the pristine device has an efficiency of 18.58% under the same conditions. This approach suggests an important direction for improving the film quality to reduce trap density and charge recombination.

Interfacial engineering is an efficient strategy for enhancing the performance of perovskite photovoltaic cells. Here, we present a novel method to modify the surface of TiO2 with thiourea. X-ray photoelectron spectroscopy indicates that thiourea treatment inactivates the TiO2 surface groups. Kelvin probe force microscopy and ultraviolet photoelectron spectra demonstrate an energy level downshift of the modified TiO2. Photoluminescence spectra reveal the reduced interface charge recombination and an improved charge transportation/extraction. Tafel and Nyquist plots elucidate a decrease of trap-state density and an increase of conductivity of the modified TiO2. Hence, the planar perovskite solar cell based on the TiO2 electron transport layer (ETL) modified with 0.1 M thiourea yields an efficiency of 19.18%, which is 7.5% larger than that of the device based on the pristine TiO2 ETL. The simple procedure and the significant performance improvement render this method promising.

Dispersible cadmium sulfide (CdS) nanoparticles are synthesized by a facile solvothermal reaction and are used for the first time as an electron transport layer (ETL) in inverted planar perovskite solar cells. The CdS ETL has superb electron extraction and transport properties, leading to a solar cell with light hysteresis and a high efficiency of 13.36%.

The 2D/3D composite structure possesses both the excellent stability of 2D perovskite and the excellent performance of 3D perovskite, which recently have attracted special attention. Different from the popular isopropanol, a novel additive solvent-polypropylene glycol bis (2-aminopropyl ether) (A-PPG) is introduced here to dissolve excess PbI

Constructing three-dimensional (3D)/two-dimensional (2D) hybrid perovskite heterojunction has been proved to be a promising approach to improve the power conversion efficiency (PCE) and environmental stability of perovskite solar cells (PSCs). Here, an organic ammonium salt, cyclohexylmethylammonium bromide (CMABr), is deposited atop the primary 3D perovskite film to form ultrathin 2D perovskite with residual PbI2 between the light-absorbing layer and the hole transport layer (HTL). The in-situ wide-band-gap 2D perovskite layer could play a multifunctional role in passivating the surface defects and protecting the underlying 3D perovskite film from humidity, resulting in the significantly suppressed non-radiative recombination process and superior moisture stability. As a result, a maximum PCE of 21.80% was obtained for the 3D/2D PSC as compared to that (19.62%) of pure 3D device. Moreover, the unencapsulated devices with 2D perovskite capping layer exhibited excellent long-term durability and mitigated hysteresis in contrast with the control device. Our study confirms that building 3D/2D perovskite heterojunctions by the utilization of organic ammonium salts is an effective way to develop highly efficient and stable PSCs.

Organic lead halide layer is crucial to a high-efficiency planar perovskite solar cell. In order to reduce defects and improve the crystallinity of the perovskite layer, we introduce formamidinium lead iodide (FAPbI3) as crystal seeds to modulate the growth of methylammonium lead iodide (MAPbI3) crystals and form a mixed-cation perovskite layer (MA1−xFAxPbI3) by a facial two-step spin-coating method. The field-emission scanning electron microscopy and X-ray diffraction pattern show the better crystallinity and larger grain for mixed-cation perovskite layer than the pristine MAPbI3 layer. Time-resolved photoluminescence decay measurements indicate that the mixed perovskite layer has less defect and longer lifetime for charge recombination than pristine MAPbI3 layer. Under optimal conditions, the planar perovskite solar cell based on MA0.5FA0.5PbI3 achieves a champion power conversion efficiency (PCE) of 19.41%, while the planar perovskite solar cell based on pristine MAPbI3 obtains a PCE of 15.95% under the same conditions.

As game-changers in the photovoltaic community, perovskite solar cells are making unprecedented progress while still facing grand challenges such as improving lifetime without impairing efficiency. Herein, two structurally alike polyaromatic molecules based on naphthalene-1,8-dicarboximide (NMI) and perylene-3,4-dicarboximide (PMI) with different molecular dipoles are applied to tackle this issue. Contrasting the electronically pull-pull cyanide-substituted PMI (9CN-PMI) with only Lewis-base groups, the push-pull 4-hydroxybiphenyl-substituted NMI (4OH-NMI) with both protonic and Lewis-base groups can provide better chemical passivation for both shallow- and deep-level defects. Moreover, combined theoretical and experimental studies show that the 4OH-NMI can bind more firmly with perovskite and the polyaromatic backbones create benign midgap states in the excited perovskite to suppress the damage by superoxide anions (energetic passivation). The polar and protonic nature of 4OH-NMI facilitates band alignment and regulates the viscosity of the precursor solution for thicker perovskite films with better morphology. Consequently, the 4OH-NMI-passivated perovskite films exhibit reduced grain boundaries and nearly three-times lower defect density, boosting the device efficiency to 23.7%. A more effective design of the passivator for perovskites with multi-passivation mechanisms is provided in this study.

Hole transport materials (HTMs) play an important role for achieving high performance and stable perovskite solar cells (PSCs). Although the state-of-the-art HTM, spiro-OMeTAD, has been successfully applied in PSCs, it exhibits an inferior conductivity and hole mobility, which hampers its future application in commercial PSCs. In this study, a common and strong inorganic oxidant, kalium persulfate (KPS), is introduced as a p-type dopant into spiro-OMeTAD for PSCs with a regular n-i-p architecture. By the introduction of KPS into spiro-OMeTAD films, we systematically investigated the morphology, optoelectrical properties and energy level of KPS-doped hole transport layer (HTL). The results indicate that the incorporation of KPS could not only oxidize spiro-OMeTAD efficiently, but also suppress ion migration by passivating the defect states at the perovskite surface. Accordingly, the KPS-modified PSC with a champion PCE of 20.23% delivered a stabilized output efficiency of 19.59%, while the control device exhibited an inferior PCE of 18.29% with a stabilized power output of 17.51%. More importantly, the devices employed KPS-doped spiro-OMeTAD exhibited less hysteresis and superior long-term stability. Our study provides an insight for HTL engineering by using a low-cost inorganic oxidant for highly efficient and stable PSCs.

The perovskite layer is the most crucial factor for the high performance perovskite solar cells. Based on solvent engineering, we develop a ternary-mixed-solvent method for the growth of high-quality [Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3] cation-anion-mixed perovskite films by introducing N-methyl-2-pyrrolidone (NMP) into the precursor mixed solution. By controlling rapid nucleation and retarding crystal growth via intermediate phase PbI2-NMP (Lewis acid-base adduct), a dense, large grain, pinhole-free and long charge carrier lifetime perovskite film is obtained. By optimizing the precursor solvent composition, the perovskite solar cell achieves an impressive power conversion efficiency of 19.61% under one-sun illumination. The research presented here provides a facile, low-cost and highly efficient way for the preparation of perovskite solar cells.

Electron transport layer (ETL) plays an important role in improving charge transportation, suppressing current-voltage hysteresis and enhancing photovoltaic performance of perovskite solar cells (PSCs). Here we successfully synthesize anatase titania nanoparticles (TiO2 NPs) with an average diameter about 3.6 nm by a facile and low-cost solvothermal method. Using the as-synthesized TiO2 NPs as ETL, the planar perovskite solar cells exhibit good photovoltaic performance. Encouragingly, when the TiO2 NPs are modified with titanium acetylacetonate [TiO(acac)2], a pinhole-free, dense, low charge transfer resistance and high charge extraction TiO2 ETL is formed and the power conversion efficiency of the planar perovskite solar cell is enhanced from 17.25% to 19.21%, accompanied by a significant decrease of J-V hysteresis. The facile process and significant performance improvement suggest that acetylacetonate modified TiO2 nanoparticles could be good ETL candidates for high-performance planar perovskite solar cells with low hysteresis.

High performance CdS sensitized TiO 2 nanorod arrays based solar cells are fabricated by polymer-assisted layer-by-layer adsorption and reaction (PA-LBLAR) method. The PA-LBLAR method can well control the deposited size of CdS on the TiO 2 nanorod arrays, which are grown on Ti foils by hydrothermal route then transferred to transparent conductive glasses. The UV–vis absorption spectra show that with the increasing deposition times, the absorption spectra of photoelectrodes increased to a broader wavelength range, which is originated by the better coverage and increased size of CdS quantum dots on the TiO 2 nanorod arrays as detected by SEM and TEM images. The highest power conversion efficiency of the cells (AM 1.5 G, 100 mWcm −2 ) up to 2.944% can be obtained with 7 cycles of PA-LBLAR deposition of CdS sensitized layers in the photoelectrodes, which is much higher than that of the best performance of cell with 14 cycles of traditional successive ionic layer adsorption and reaction processes.

The organic–inorganic lead halide layer is a crucial factor in determining the photovoltaic performance of perovskite solar cells. Based on solvent engineering, we developed a three-step sequential coating method to prepare a high-quality CH3NH3PbI3 layer based on solvent (isopropanol) substitution. Stonehenge-like PbI2 nanostructures with controllable morphology and crystallinity were prepared by solvent substitution instead of the conventional annealing-treatment, affording several channels for CH3NH3I to penetrate into the PbI2 film due to volume expansion, and thus enabling the complete conversion from PbI2 to perovskite. In addition, the device exhibited high reproducibility by our method and achieved a high 17.78% power conversion efficiency under one-sun illumination. Furthermore, we optimized the production craft and successfully fabricated a uniform perovskite film (10 cm × 10 cm) via solvent substitution.

A TiO 2 compact layer is crucial to a high-performance perovskite solar cell (PSC). Interestingly, there is a severe paucity of research on using one-dimensional nanostructure to fabricate the compact layer. In this study, anatase TiO 2 single-crystalline nanorods (NRs) with a length of 30 ± 10 nm and a diameter of 4 ± 1 nm are synthesized via a one-pot solvothermal approach. A pinhole-free and thickness-controllable compact layer on PSC is fabricated by spin-coating the TiO 2 nanorods on transparent conductive oxide substrate. Thanks to good electronic transport channel and less defects and interfaces, one-dimensional TiO 2 NRs, with longer electron lifetime, shorter transport time and higher charge collection efficiency than TiO 2 quantum dots (QDs) and TiO 2 nanoparticles (NPs), can improve the photovoltaic performance of the PSC based on TiO 2 -NR compact layer. As a result, the PSC based on TiO 2 NRs shows the best photovoltaic performance with a power conversion efficiency of 17.58%, which is enhanced by a factor of 1.16 and 1.30 respectively compared with the PSCs based on TiO 2 -QDs and TiO 2 -NPs.

Organolead halide perovskite solar cells with mesoporous metal oxide films as support layers have made great achievements in the field of solar cells in recent years. Here, tin oxide (SnO 2 ) nanosheets are prepared by hydrothermal method. The as-synthesized SnO 2 nanosheet layer is used as electron-transporting material to replace traditional TiO 2 mesoporous layer in perovskite solar cells. The crystallizing time of CH 3 NH 3 PbI 3 on SnO 2 is investigated and optimized as 10 min. The surface of SnO 2 nanosheets is treated with TiCl 4 aqueous solution, which improves the photovoltaic performance of the perovskite solar cells. The SnO 2 nanosheet-based perovskite solar cell achieves excellent photovoltaic parameters: short-circuit current density of 17.58 mA cm −2 , open-circuit voltage of 1.01 V, and power conversion efficiency of 7.81%.

It is well-known that solution-processed polycrystalline perovskite films show a high density of parasitic traps and the defects mainly exist at grain boundaries and surfaces of polycrystal perovskite films, which would limit potential device performance by triggering the undesired recombination and impair device long-term stability by accelerating the degradation of perovskite films. In this regard, defect passivation is highly desirable for achieving efficient and stable perovskite solar cells (PSCs). Here, we report the fabrication of highly reproducible, efficient, and stable PSCs via interface engineering with CoO nanoplates. When a suitable concentration of CoO nanoplates solution is spin-coated on perovskite film, a discontinuous CoO nanoplates modified layer is obtained, which is advantageous to achieving highly photovoltaic performance of the device because the uncovered perovskite crystalline grains can guarantee the unobstructed transport of holes from perovskite layers to hole transport layers. Furthermore, the hydrophobic oleylamine ligands capped CoO nanoplates are well filled in the boundaries of perovskite crystalline grains to effectively passivate the trap states, suppress dark recombination, and enhance moisture-resistance. These benefits are propitious to achieving a 20.72% champion efficiency and a 20.20% steady-state efficiency of the devices with good reproducibility and stability.

Two approaches are utilized to alter the Si/Al ratio of zeolite on ceramsite: one is altering the Si/Al ratio of ceramsite and the other is adding extra silicate/aluminate during the hydrothermal reaction. The results show that the former method has no significant effect on the type of prepared zeolite, however, the latter one has been proved to be effective. The growth of zeolites conforms to the liquid phase transformation mechanism according to the researching results: 1) the Si and Al for zeolite synthesis were not only from the dissolved Si and Al element from ceramsite but also from the silicate/aluminate added; 2) the phase of zeolite grew on ceramsite would be changed with the proportion of Si/Al (zeolite P1 modified ceramsite at low Si/Al ratio, then chabazite modified ceramsite, and zeolite P modified ceramsite at high Si/Al ratio); 3) zeolite formed in the bulk solution is quite different from the zeolite formed on ceramsite due to diffusion limitation.

Lithium bis (trifluoromethane sulfonyl) imide (Li-TFSI) and 4-tert-butyl pyridine (TBP) doped 2,2′,7,7′-tetrakis (N, N-p-dimethoxy-phenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD) is the most commonly used hole-transporter in perovskite solar cells (PSCs). Although the introduction of both Li-TFSI and TBP can significantly enhance the conductivity of spiro-OMeTAD and thereby improve the power conversion efficiencies (PCEs) of PSCs, the dopants unfortunately render hysteresis and reduce stabilities of PSCs. In this paper, we have synthesized hydrophobic p-type PbS nanocrystals and prepared a binary hole-transporter by mixing PbS and Spiro-OMeTAD (PbS/Spiro-OMeTAD), which therefore avoids the use of traditional hygroscopic Li-TFSI and volatile TBP dual additives. The PbS/Spiro-OMeTAD exhibits excellent conductivity and well-matched valence band with that of perovskite. PSCs incorporating PbS/Spiro-OMeTAD as the hole transporting layer (HTL) can obtain a highest PCE of 20.11% and show excellent long-term stability, which is much better than the controlled device with Li-TFSI and TBP doped Spiro-OMeTAD as the HTL.

The preparation of high-quality perovskite thin films with low grain boundaries and defect states plays an important role in determining the photovoltaic performance and stability of perovskite solar cells (PSCs). It has been proved that the inorganic CsPbBr3 perovskite material has unique stability. However, the wide band gap and small light absorption range limit the power conversion efficiency (PCE) of the corresponding devices. Here, we report that the addition of guanidine iodide (GAI) into CsPbBr3 precursor solution can greatly improve the quality of CsPbBr3 film, leading to inhibition of interfacial recombination, promotion of charge migration and reduction of trap state density. Ultimately, the planar PSC with GAI modified CsPbBr3 film yields a champion efficiency of 8.54%, much higher than the control one (6.56%).

The ionic nature of the perovskite material results in a great number of defects in the perovskite film which limits the efficiency and stability of perovskite solar cells. The passivation of the defects can effectively suppress the non-radiative recombination of carriers and improve the photovoltaic performance and stability of perovskite solar cells. In this paper, quinoline is introduced into the perovskite precursor solution. By adjusting the addition amount, it is found that quinoline can effectively induce the growth and orientation of perovskite crystals, consequently, improving the film quality and reduce defect density. The optimized device shows higher VOC (1.142 V) and FF (0.792), and achieved a champion power conversion efficiency of 20.87%. In addition, the hysteresis of the device is suppressed and the stability is improved. The results demonstrate that quinoline is an effective perovskite additive.

Organic-inorganic hybrid perovskite solar cells (PSCs) have gradually occupied an important position in the field of new generation photovoltaic devices after years of development. However, the performance and stability of the device are still the key issues restricting its commercialization, and interface engineering is one of the attractive methods. Here, we applied π-conjugated 5-(Fmoc-amino) valeric acid (Fmoc-5-AVA) to post-treat the perovskite films for preparing high efficient and stable PSCs. The photovoltaic performance and stability of the PSCs are enhanced by spin-coating appropriate concentration of ethyl acetate solution of Fmoc-5-AVA on the perovskite films, which are owing to the passivation reduced defects and trap density. The optimal efficiency of the modified PSC is 21.21%, much higher than the unmodified one (19.05%).

SrTiO 3 nanotube films with good adhesion strengths to Ti substrates were fabricated by using a hybrid approach with a modified anodization and a hydrothermal treatment (HT). The effect of Sr 2+ concentration in HT solutions on the morphologies and phase components of the nanotubes were investigated, the SrTiO 3 nanotubes formation mechanism was explored, and the adhesion strengths, hydrophilicity and apatite-forming ability of the SrTiO 3 nanotubes were also evaluated. The results demonstrated that with increasing the incorporation of Sr 2+ into the nanotubes, no obvious changes of the lengths and outer diameters of the nanotubes were observed, but the wall thickness and the crystallinity of SrTiO 3 in the nanotubes increased. The accumulation of Sr at the inner tube wall indicated that the reaction of Sr 2+ with TiO 2 mainly occurred in the vicinity of internal surfaces of the closely arranged nanotubes. The formation of the SrTiO 3 nanotubes could be attributed to an in situ dissolution–recrystallization process. The SrTiO 3 nanotubes exhibited good hydrophilicity and bioactivity, and the induced apatite preferred to nucleate on the nanotubes with higher crystallinity and Sr content, indicating a good bio-adaptability of the SrTiO 3 nanotubes for orthopedic application.

Metal dichalcogenide has a layered structure, which is endowed with versatile and tunable photoelectrochemical properties. In this paper, molybdenum diselenide (MoSe2) is synthesized by the solvothermal method, and the as-synthesized MoSe2 shows microsphere hierarchical architecture composed of 2-D nanosheets. The electrochemical characterization indicates that the MoSe2 electrode has lower resistances and better electrocatalytic activity toward triiodide/iodide redox reaction than the traditional Pt electrode. Using the MoSe 2 as a counter electrode in the dye-sensitized solar cell (DSSC), a high-power-conversion efficiency of 9.80% is achieved, outperforming the DSSC-based traditional Pt counter electrode (8.17%). Moreover, using the MoSe2 as an electrode in the supercapacitor, it displays a high specific capacitance of 272 F⋅g−1.

Highly ordered TiO 2 nanotube arrays are synthesized and utilized in preparing front-side illuminated photoelectrodes of CdS quantum-dot-sensitized solar cells (QDSSCs). The CdS quantum dots (QDs) are adsorbed on the ordered TiO 2 nanotube arrays by successive ionic layer adsorption and reaction method (SILAR). Taking the advantages of high surface area and large size of ordered pores of the TiO 2 nanotube arrays, the reaction solutions for SILAR processes can easily penetrate into the photoelectrodes; and the formed CdS QDs can be homogeneously dispersed on the TiO 2 nanotube walls with high coverage. In order to improve photovoltaic performance of QDSSCs, the other important components including counterelectrode, polysulfide (S 2− / S x 2 - ) electrolyte, and cycles of SILAR processes for preparing CdS QDs sensitized photoelectrodes are optimized. With thermally treated CuS counterelectrode, pure deionized water based polysulfide (S 2 − / S x 2 - ) electrolyte, and 15 cycles of SILAR processes prepared CdS QDs sensitized photoelectrode, the QDSSC can achieve the highest power conversion efficiency about 3.22% under full sunlight illumination (100 mW cm −2 , AM 1.5G), which is a comparative value among the pure CdS QDs sensitized solar cells.

3,4-Ethylenedioxy thiophene (EDOT) precursor solution doped by Fe3O4 was spin-casted onto fluorine doped tin oxide (FTO) glass and formed poly(3,4-ethylenedioxy thiophene) (PEDOT)/Fe3O4 hybrid films by an in situ polyreaction. The films were utilized as the counter electrode in dye sensitized solar cells (DSSCs). Photoelectric conversion efficiency (PCE) for DSSCs based on PEDOT/Fe3O4 varied with the content of Fe3O4 in the precursor solution. When the content of Fe3O4 was 2 mg ml−1 in the precursor solution (PEDOT/Fe3O4-2), the best performance (8.69%) was obtained. In comparison, that of a DSSC with a Pt counter electrode is 8.35%. According to the surface microtopography and electrochemical analysis, large active areas, consecutive electronic transmission channels and lower charge transfer resistance could be responsible for the high PCE.

High-performance counter electrodes for dye-sensitized solar cells (DSSCs) are fabricated with platinum-nickel oxide (Pt-NiO) nanosheets as catalytic materials. Firstly, the Pt-Ni nanosheets are synthesized via galvanic replacement reaction between pre-synthesized Ni nanosheets and an aqueous H2PtCl6 solution. Secondly, after thermal treatment in air, the Pt-Ni alloys are turned to Pt-NiO nanosheets. The related data of cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization reveal that Pt-NiO counter electrodes show highly catalytic activity and low charge transfer resistance. The DSSC with Pt-NiO counter electrode exhibits power conversion efficiency (PCE) of 8.40 %, which is lower than that of the DSSC containing commercial available Pt counter electrode (9.15 %) under full sunlight illumination (100 mW cm−2, AM1.5G). However, owing to the extremely high transparency of Pt-NiO counter electrode, when putting an Ag mirror behind the back side of the DSSC, the reflected light can bring great enhanced PCE (11.27 %).

Numerous studies identify that charge-carrier nonradiative recombination of defects restrains the photovoltaic performance of the devices. Herein, a novel interfacial modifier iodobenzene diacetate (DAIB) is used to mitigate the defects and improve charge carrier transportation at the interface between the perovskite layer and hole transporting layer. The surface morphology and crystalline state of perovskite are observed, the photoelectrochemical characterizations of the perovskite films are investigated, and the reaction mechanism of DAIB and the energy band change of the perovskite films are estimated. It is indicated that the DAIB modification can reduce the defect and nonradiative recombination, hence the hole extraction ability is improved. Therefore, a planar perovskite photovoltaic device interfacial modified with DAIB generates a maximum power conversion efficiency (PCE) of 20.08%, and the pristine device obtains an efficiency of only 18.19%. This research demonstrates an efficient and low-cost strategy for generating high-performance perovskite solar cells.

Cobalt selenide (CoSe 2 ) nanorods are prepared by hydrothermal method and used as an efficient Pt-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). Field emission scanning electron microscopy observes that CoSe 2 mostly exhibits a nanorod morphology, which facilitates change carrier transfer from their surface to redox electrolyte. Cyclic voltammogram measurement indicates that CoSe 2 electrode has larger current density than Pt electrode. Electrochemical impedance spectroscopy shows that the CoSe 2 electrode with optimal condition has low series resistance of 8.034 Ω × cm 2 and has low charge-transfer resistance of 0.097 Ω·cm 2 . Under simulated solar light irradiation with intensity of 100 mW·cm −2 (AM 1.5), the DSSC based on the CoSe 2 CE achieves a power conversion efficiency of 8.38 %, which is higher than the solar cell based on Pt CE (7.83%).

A petal-like cobalt selenide nanosheets (Co0.85Se) is prepared by hydrothermal method and used as an efficient Pt-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). Field emission scanning electron microscopy observes that the petal-like Co0.85Se possess porous and large specific surface area, which benefits the enhancement of electrocatalytic activity. Cyclic voltammogram measurement indicates that Co0.85Se electrode has larger current density than Pt electrode. Electrochemical impedance spectroscopy shows that the Co0.85Se electrode with optimal condition has low charge-transfer resistance of 0.79 Ω cm2. Under simulated solar light irradiation with intensity of 100 mW cm−2 (AM 1.5), the DSSC based on the Co0.85Se CE achieves a power conversion efficiency of 8.00 %, which is slightly higher than the solar cell based on the Pt CE (7.83 %).

CoMoO4/Co9S8 hybrid nanotubes were fabricated by a simple two-step hydrothermal method, which was similar to that for preparing Co9S8 nanotubes. Then the CoMoO4/Co9S8 nanotubes were coated onto fluorine-doped tin oxide glass to fabricate a counter electrode (CE) by spin-casting. Field emission scanning electron microscopy images show that the introduction of CoMoO4 to Co9S8 makes the surface of the CoMoO4/Co9S8 nanotubes rougher. Cyclic voltammetry shows that the electrocatalytic activity of the CoMoO4/Co9S8 CE is similar to that of a Pt CE when the (NH4)2MoO4 content was 60 wt%. Meanwhile, the electrochemical impedance spectroscopy and Tafel measurements demonstrated that the CoMoO4/Co9S8 CE had smaller values of Rs and Rct than a Pt CE. The dye-sensitized solar cells assembled with a CoMoO4/Co9S8 CE achieved excellent values of open-circuit voltage (0.743 V), short-circuit current density (17.276 mA cm−2), fill factor (0.670) and a wonderful power conversion efficiency (8.60%), which is higher than that of DSSCs with a Co9S8 CE (7.69%) or a Pt CE (8.13%) under the light intensity of 100 mW cm−2 (AM 1.5 G).

Composite film of poly(3,4-ethylenedioxythiophene)/platinum (PEDOT/Pt) with high efficient is electrodeposited onto rigid fluorine-doped tin oxide substrate by using a facile approach of one step electrochemical polymerization, and its application as counter electrode (CE) in dye-sensitized solar cell (DSSC). The DSSC based on the PEDOT/Pt counter electrode exhibited a high power conversion efficiency of 7.86% under illumination of 100 mW cm−2, which is higher 13.09% than that of the DSSC based on Pt electrode (6.95%). The extensive electrochemical analyses for the PEDOT/Pt CE made from cyclic voltammetry, electrochemical impedance spectroscopy measurements, and Tafel curves reveal that the PEDOT/Pt hybrid CE possesses high electrocatalytic activity for the reduction of triiodide to iodide and low charge-transfer resistance on the counter electrode–electrolyte interface. Therefore, the PEDOT/Pt CE can be considered as a promising alternative CE for DSSCs.

The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3−xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3−xBrx film.

Nanographite/polypyrrole (NG/PPy) composite film was successfully prepared via in situ polymerization on rigid fluorine-doped tin oxide substrate and served as counter electrode (CE) for dye-sensitized solar cells (DSSCs). The surface morphology and composition of the composite film were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectra and Fourier transform infrared spectroscopy (FTIR). The electrochemical performance of the NG/PPy electrode was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results of CV and EIS revealed that the NG/PPy electrode possessed excellent electrocatalytic activity for the reduction reaction of triiodide to iodide and low charge transfer resistance at the interface between electrolyte and CE, respectively. The DSSC assembled with the novel NG/PPy CE exhibited an enhanced power conversion efficiency of 7.40% under full sunlight illumination as comparing to that of the DSSC based on sputtered-Pt electrode. Thus, the NG/PPy CE could be premeditated as a promising alternative CE for low-cost and high- efficient DSSCs.

A new kind of photoactive electrodes with nanocrystalline TiO2 (nano-TiO2) secondary structure is successfully prepared via a simple method of adding a small amount of TiCl4 2-propanol solution in conventional nano-TiO2 paste to form micro-sized nano-TiO2 aggregates. The benefits of this special structure include improved optical absorption, increased light scattering ability, and enhanced electron transport and collection efficiency. Dye-sensitized solar cells (DSCs) based on these photoactive electrodes show improved performance. The power conversion efficiency of the cells can be increased from 5.03% to 7.30% by substituting 6 μm conventional nano-TiO2 thin film with the same thickness of as-prepared nano-TiO2 aggregates film in the photoactive electrodes. A higher power conversion efficiency of the cells can be obtained by further increasing the thickness of the nano-TiO2 aggregates film.

A microporous hybrid polymer of poly(acrylic acid)-g-poly(ethylene glycol)/polyaniline (PAA-g-PEG/PANI) is synthesized by a two-step solution polymerization method. The influence of aniline concentration on the conductivity of PAA-g-PEG/PANI gel electrolyte is discussed, when the concentration of aniline is 0.66 wt%, the conductivity of PAA-g-PEG/PANI gel electrolyte is 11.50 mS cm−1. Using this gel electrolyte as host, a quasi solid state dye-sensitized solar cell (QS-DSSC) is assembled. The QS-DSSC based on this gel electrolyte achieves a power conversion efficiency of 6.38% under a simulated solar illumination of 100 mW cm−2 (AM 1.5). POLYM. ENG. SCI., 55:322–326, 2015. © 2014 Society of Plastics Engineers

Polyaniline (PAn) nanobelts were synthesized by simply mixing aniline and hydrochloric acid aqueous solution with ammonium peroxydisulfate and hydrochloric acid aqueous solution at room temperature without any templates. The PAn nanobelt paste with polytetrafluoroethylene as binder is proper for low-cost and efficient casting processes such as doctor blade method, screen printing, spin-casting, and even roll-to-roll painting. The porous network structure of the PAn nanobelt counter electrode was obtained after drying the paste on the conductive glass. The as-prepared PAn nanobelt counter electrode showed nearly equivalent electrochemical catalytic activity as that of thermal decomposed Pt counter electrode, owing to the well-connected conductive network and high active surface area. The power conversion efficiency of dye-sensitized solar cell with PAn nanobelt counter electrode attained 90% of the value of the cell with Pt counter electrode. Copyright © 2014 John Wiley & Sons, Ltd.

Due to the rough surface of fluorine-doped tin oxide (FTO) conductive glasses, it is challenging to fabricate fully covered ultra-thin hole-transport layer (HTL) with thickness under 100[Formula: see text]nm by a simple solution-processed method. Yet, the quality of HTLs play a key role in determining photovoltaic performance of the inverted planar perovskite solar cells (PSCs) owing to their important functions for effectively extracting holes, blocking electrons, suppressing dark reaction, and so on. Here, we report a facile nickel-containing organic sol (Ni–Sol) route to fabricate fully covered 46[Formula: see text]nm thick NiO HTLs for efficient inverted planar PSCs. Comparing with the pre-synthesized NiO nanocrystals solution, the Ni–Sol is easier to spread around the rough outline of FTO to achieve higher surface coverage. Through optimizing the concentration of nickel-containing organic sol, the champion performance of the inverted planar PSCs can be achieved because of the high transparency and good hole-transport dynamics of the optimized NiO film. This work demonstrates the advanced Ni–Sol route for preparing efficient inverted planar PSCs by the simple solution-processed method.