Search

Though perovskite solar cells (PSCs) or modules (PSMs) are being developed at an unprecedented speed, several obstacles remain to their commercialization. One of the difficult problems is the expensive and unstable Au and Ag counter electrode. Therefore, highly effective, stable, and low‐cost counter electrode materials should be explored. Among various counter electrode materials, carbon is one of the most promising substitutes for their rich sources, low cost, outstanding electrochemical performance, and diversified surface functions. This review summarizes recent achievements of carbon counter electrode materials, which included commercial carbon paste, carbon black, graphite, graphene, carbon nanotubes and their synthetic approaches, modifications, and structure‐function relationships. Moreover, large‐scale carbon counter electrode in PSCs or PSMs are specifically discussed. Hopefully, this recapitulative analysis will draw the attention of relevant researchers to re‐understand the importance of counter electrode and clarify what should be noticed to develop qualified counter electrode materials for PSCs or PSMs. [ABSTRACT FROM AUTHOR]

Doping transition metal ions into polyaniline (PANI) as an attractive electrode material have been regarded as one of the crucial factors to improve the capacitive performance and the cycle stability of supercapacitors due to their excellent metal properties and good conductivity. Herein, PANI has been prepared via in situ facile and low‐cost electro‐polymerization method. At a current density of 0.2 A g−1, the supercapacitor using PANI electrode shows the specific capacitances of 203.0 F g−1 in 1 M H2SO4 electrolyte. To further improve the electrochemical activity of PANI electrode, the transition metal ions M2+ (M2+ = Ni2+, Co2+, Mn2+, and Cu2+) have been doped into PANI electrode via the same electro‐polymerization method. And the supercapacitor with the different doped‐PANI electrode generates the specific capacitances of 364.3, 326.1, 258.5, and 250.6 F g−1 respectively from PANI‐Ni2+, PANI‐Co2+, PANI‐Mn2+, and PANI‐Cu2+, which were superior to 79.5%, 60.6%,27.3%, and 23.4% of the pristine PANI based counterpart under the same test conditions and method. The favorable performances make the different doped‐PANI act as a new resource of the high performance electrode materials of supercapacitor. [ABSTRACT FROM AUTHOR]

Replacing the expensive Pt catalyst of counter electrodes (CEs) with a low-cost Pt-free catalyst has been regarded as one of the crucial steps for cost effectiveness of dye-sensitized solar cells (DSSCs). Herein, MnWO4 as a binary mixed oxide (MnO–WO3) has been prepared with (NH4)10H2(W2O7)6·xH2O and Mn(NO3)2·4H2O via a facile hydrothermal method. DSSCs using MnWO4 CEs show power conversion efficiency (PCE) of 4.93%. To improve the catalytic activity of MnWO4 CEs further, three proportions of MnWO4@AC mixed oxide composite catalysts have been fabricated via simple physical mixing MnWO4 with activated carbon (AC) by ball-milling. Moreover, the DSSCs with the MnWO4@AC composites CEs generate high PCE of 6.50, 6.45 and 6.12%, respectively, from MnWO4 : AC mass ratios of 1 : 2, 1 : 1 and 2 : 1 for the regeneration of traditional iodide/triiodide (I3−/I−) redox couples, which were superior to the pristine MnWO4, Pt- and AC-based counterpart 4.93%, 4.54% and 2.10% CEs under the same test conditions and method. The favorable performances make MnWO4@AC composites act as a new resource of electro-catalytic Pt-free materials for high-performance CEs in the encapsulation of DSSCs. [ABSTRACT FROM AUTHOR]

In this study, 2D layer‐structured Ti3C2 is synthesized by using an etching method at lower temperature, which is then applied in dye‐sensitized and perovskite solar cells as counter electrode with higher activity compared with conventional TiC particles counter electrode. The dye‐sensitized solar cells fabricated by using a 2D layer‐structured Ti3C2 counter electrode achieves a power conversion efficiency of 9.57 %, much higher than that of the counterpart device fabricated using a TiC particle counter electrode (7.37 %). The excellent activity of the Ti3C2 electrode can be attributed to the superior charge transfer and mass transport properties, owing to the specific 2D layer structure. Moreover, the fabricated 2D layer‐structured Ti3C2 is applied in perovskite solar cells, thereby achieving a power conversion efficiency of 7.78 % without further optimization. Thus, it is a potential candidate for noble metal electrodes. [ABSTRACT FROM AUTHOR]

• MoO 2 spheres with a novel mesoporous structure is fabricated for supercapacitor. • The capacitive behavior of MoO 2 and MoO 3 are evaluated and compared. • The MoO 2 shows a specific capacitance of 381.0 F g−1, 7 times higher than MoO 3. MoO 2 and MoO 3 with specific morphologies are synthesized on flexible carbon cloth through a facile hydrothermal method as supercapacitor electrodes. The prepared prismatic MoO 3 shows a specific capacitance of 54.7 F g−1 in 1 M LiOH electrolyte. Moreover, the prepared MoO 2 presents a spherical profile with hierarchical porous structure. Each MoO 2 sphere is stacked with several layers of MoO 2 "spindle" which is further built by amounts of MoO 2 nanoparticles. A high specific capacitance of 381.0 F g−1 is achieved for the MoO 2 sphere electrode, 7 times higher than that of MoO 3. [ABSTRACT FROM AUTHOR]

To increase the competitiveness of quantum-dotsensitized solar cells (QDSCs) among the various photovoltaic devices, it is necessary to develop new counter-electrode (CE) catalysts to replace the unviable Pt CE. Herein, a series of metalsulfide spheres (e.g., FeS2, Co9S8, NiS, CuS, and ZnS) are designed and synthesized as CE catalysts for QDSCs. As inferred from cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization-curve results, except for ZnS, all of the sulfide spheres perform better than Pt toward Sx 2-/S2- redox-couple regeneration, among which, NiS shows the highest catalytic activity, followed by Co9S8, CuS, and FeS2. The power conversion efficiencies of ZnO nanorod-array photoanode-based QDSCs with sulfide-sphere CEs are 2.5 % (NiS), 2.2 % (Co9S8), 1.8 % (CuS), and 0.8 % (FeS2), much higher than that of their Pt CE-based counterparts (0.30 %). [ABSTRACT FROM AUTHOR]

Novel polyaniline (PANI) nanofiber counter electrodes (CEs) modified with different transition metal ions were synthesized and showed remarkable catalytic activity for dye-sensitized solar cells (DSSCs). The PANI nanofiber-transition metal ion electrodes were characterized by using Fourier transform infrared spectroscopy, scanning electron microscopy, current density-voltage curves, energy-dispersive X-ray spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization plots. The PANI CEs modified with Ni2+ and Co2+ exhibited low charge-transfer and series resistances, which indicate high electrocatalytic activity toward the iodide redox shuttle. In contrast, the PANI CE modified with Mn2+ did not show much difference in its catalytic behavior, whereas the PANI-Cu2+ CE showed reduced electrochemical performance. The photovoltaic performances of the DSSCs based on the PANI-Ni2+ and PANI-Co2+ CEs were evaluated and they were found to exhibit power conversion efficiency of 4.70 and 4.57 %, higher than that of the pristine PANI-CE-based device (3.87 %). These easily fabricated PANI-metal composites with improved electrochemical activities are promising CEs for DSSCs to replace expensive Pt. [ABSTRACT FROM AUTHOR]

Titanium carbide (TiC) has been used as a counter electrode (CE) catalyst in place of Pt for triiodide reduction in dye-sensitized solar cells (DSCs). Its catalytic activity can be comparable to that of Pt. The effect of the thickness of the TiC layer on the performance of the DSCs was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and Tafel polarization measurements. We found that as the film thickness increased, the fill factor and short-circuit current density increased, which led to improved power-conversion efficiency. When the TiC film was thicker than 20 μm, however, no significant continuous improvement in the catalytic activity was observed. A high power-conversion efficiency of 6.46 % was obtained for the DSC by using a TiC CE at the optimized film thickness, a value similar to that obtained with a Pt CE. [ABSTRACT FROM AUTHOR]

Synthesized niobium oxides (Nb2O5and NbO2) were applied for the first time as counter electrodes (CEs) in dye-sensitized solar cells (DSCs). The DSC using NbO2CE showed a higher power conversion efficiency of 7.88%, compared with that of the DSC using Pt CE (7.65%). [ABSTRACT FROM AUTHOR]

Tungsten dioxide (WO2) nanorods were synthesized, which showed excellent catalytic activity for the reduction of triiodide to iodide. The dye-sensitized solar cell (DSC) using WO2as a counter electrode (CE) reached a high energy conversion efficiency of 7.25%, which can match the performance of the DSC based on a Pt CE. [ABSTRACT FROM AUTHOR]

A composite electrode of poly(3,4‐ethylenedioxythiophene) (PEDOT)@4A‐molecular sieve is synthesized by a simple electrochemical polymerization method for supercapacitor applications. The prepared PEDOT@4A‐molecular sieve composite exhibits excellent capacitive behavior, with high reversibility in the electrochemical window from −0.8 V and 0.2 V. The specific capacitance of the PEDOT@4A‐molecular sieve composite electrode reaches 163.4 F g−1 at 0.25 A g−1, that is much higher than those of the pristine 4A‐molecular sieve (14.8 F g−1) and PEDOT (117.0 F g−1) electrodes at the same conditions. The composite electrode also presents excellent cycle stability, and the specific capacitance retains 82.8% of its initial value after continuous 1000 charge‐discharge cycles. This work indicates that synthesis of a composite electrode is a promising approach for enhancing the electrochemical properties of the supercapacitor electrode due to the synergistic effect. [ABSTRACT FROM AUTHOR]

Vanadium-based carbides have been applied as Pt-free counter electrodes (CEs) electro-catalysts for dye-sensitized solar cells (DSSCs) due to the advantages of earth-abundant reserves, diverse composition, ease modification, and low cost. Herein, the polyoxovanadate (NH 4) 2 V 6 O 16 as V source assisted by dicyandiamide (C 2 H 4 N 4) as C source via simply physical mixing by ball-milling to assemble VC@C precursors. And then, five different VC@C composites derived from precursors with mass ratios of dicyandiamide to polyoxovanadate of 5:1, 10:1, 15:1, 20:1 and 25:1 at 900 °C, and further achieved power conversion efficiencies (PCEs) of 5.4%, 5.6%, 6.6%, 6.2% and 5.1% as CEs for regenerate traditional I 3 −/I− couple in the encapsulated DSSCs, respectively. The effects of different mass ratio of dicyandiamide on the catalytic performances of VC@C composite CEs were also assessed using cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization experiments. The photocurrent-photovoltage (J - V) results indicated that VC@C composites CEs had high conductivity and rich number of active sites, which indicated that VC@C composites could be a cost-effective and high-performance alternative Pt-based CEs catalyst for DSSCs. • The pyrolysis of polyoxovanadates assisted by C 2 H 4 N 4 to derive VC@C composites. • VC@C composites were designed as counter electrode by the mass ratio optimized. • The obtained VC@C-3 has high conductivity and rich active sites. • The DSSCs with VC@C-3 composites CEs had the highest PCE of 6.6%. [ABSTRACT FROM AUTHOR]

Abstract: Binary composite of Pt decorated transition metal compounds (WO2, TiC, and VN) were introduced into dye-sensitized solar cells and excellent performance were obtained, almost 20% better than unitary materials. Ternary composite of Pt/WO2/TiO2 was also prepared to further improve the photovoltaic performance. [Copyright &y& Elsevier]

• MCNT x composites were prepared by well-defined Mo 2 C anchored on multi-walled carbon nanotubes. • Favorable synergistic effect between Mo 2 C and CNTs boost electrocatalytic activities of MCNT x. • The DSSCs with MCNT x based CE achieved the highest PCE of 8.06 %. Multicomponent synergistic regulation has been an effective strategy to enhance the electrochemical properties of Mo 2 C-based counter electrode (CE) catalysts in dye-sensitized solar cells (DSSCs). Herein, Mo 2 C/CNTs composites (termed MCNT x , x = 2, 4, 6, 8, means the phosphomolybdic acid (PMo 12) concentration) have been prepared using well-crystallized Mo 2 C nanograins anchored on the wall of multi-walled carbon nanotubes (CNTs) by a facial two-step approach. Through simple ultrasound assistance, PMo 12 was spontaneously connected with CNTs, and the obtained precursors can be converted to the target product MCNT x by a simple thermal decomposition at N 2 atmosphere. The modified CNTs guarantees the fast transfer of electrons and serves as framework for the support of Mo 2 C nanoparticles and mass diffusion, moreover the well-defined Mo 2 C nanoparticles ensures more accessible active sites to promote the triiodide reduction reaction (IRR). As a result of the synergistic effect between modified CNTs and Mo 2 C nanoparticles, MCNT x show excellent power conversion efficiency (PCE) when fabricated as CEs of DSSCs. The MCNT6-based DSSC exhibits a superior PCE up to 8.06 %, which is significantly higher than DSSC assembled with Pt CE (7.19 %). [ABSTRACT FROM AUTHOR]

The different surface terminals, sizes, and sheet quality of laminated 2D-Ti 3 C 2 -MXenes were prepared by selective etching intermediate Al atoms layer form the strongly bonded compound Ti 3 AlC 2 as precursor at low temperature using different etchants of HF, HF + HCl, LiF + HCl, and NH 4 HF 2 for 24 h, respectively. Then, 2D-Ti 3 C 2 -MXenes were further instead of traditional Pt as counter electrodes (CEs) in triiodide reduction for dye-sensitized solar cells (DSSCs). The selection of different etchant directly affects the properties and performance of the laminated 2D-Ti 3 C 2 -MXenes catalyst. Herein, the DSSCs with 2D-Ti 3 C 2 -MXenes CEs yielded power conversion efficiencies (PCE) of 7.15 % (HF-), 6.06 % (HF + HCl-), 6.38 % (LiF + HCl-), and 6.05 % (NH 4 HF 2 -) for regenerate traditional I 3 −/I− shuttles via the photocurrent-voltage (J - V) test, respectively. The outstanding electrocatalytic performances of laminated 2D-Ti 3 C 2 -MXenes can be attributed to the formation of regular inter-stratification structures by etching to expose larger specific surface areas and further generate more catalytic reaction sites, as well as the acceleration of I 3 −/I− shuttle diffusion channels by adjusting the interlayer d -spacing, implying a potentially candidate of Pt catalyst for applications in the encapsulated DSSCs as Pt-free CEs. [Display omitted] • HF, HF + HCl, LiF + HCl, and NH 4 HF 2 as etchants removed the Al layers of Ti 3 AlC 2. • 2D-Ti 3 C 2 -MXenes were prepared by etching Ti 3 AlC 2 with different etchant for 24 h. • The prepared 2D-Ti 3 C 2 -MXenes exhibited a laminated structure. • The laminated HF-Ti 3 C 2 MXene existed high conductivity and rich active sites. • The DSSCs with HF-Ti 3 C 2 CEs achieved the highest PCE of 7.15 %. [ABSTRACT FROM AUTHOR]

• V 2 O 3 @C composites were prepared by the pyrolyzed of the soluble starch with V 2 O 5. • It exhibits high PCE of 5.13 % than 4.54% of Pt CEs based DSSC. • V 2 O 3 @C composites are a prospective alternative of Pt-free CEs in DSSCs. The traditional counter electrodes (CEs) catalysts are mainly noble Pt-based materials, but their scarcity and high cost impede their practical applications, especially in dye sensitized solar cells (DSSCs). Hence, identifying Pt-free catalyst materials for CEs have been regarded as one of the crucial steps to improve energy conversion efficiency and cost effectiveness of DSSCs. Herein, a feasible one-step reduction was put forward to prepare V 2 O 3 @C composites utilizing V 2 O 5 as metal sources, and the soluble starch as carbon source. The four V 2 O 3 @C composite catalysts have successfully been prepared and further were applied to CEs as catalytic materials in the encapsulation of DSSCs. The power conversion efficiencies (PCE) of 2.79, 3.94, 5.13 and 4.97% were respectively obtained from mass ratios of the soluble starch to V 2 O 5 with 1:2, 1:1, 2:1 and 4:1 as counter electrode for the regeneration of I 3 −/I− redox couples. The enhanced performance can be ascribed to the number of active catalytic sites and the distribution channels on the V 2 O 3 @C composites CEs, which was caused by that the larger surface area and higher conductivity of amorphous C from the pyrolyzed carbonization of the soluble starch in the precursor. [ABSTRACT FROM AUTHOR]

Molybdenum-based carbides, as one of the representatives of transition metal compounds, are a promising alternative to the expensive and resource constrained Pt-based counter electrode (CE) in dye-sensitized solar cells (DSSCs). Herein, a series of hierarchical α-MoC 1- x @N-doped carbon (MDNC) composites are transformed from the step-by-step pyrolysis of uniformly Mo-based compounds and dopamine precursors at the temperatures of 650, 750, 850, and 950 °C under N 2 atmosphere, respectively. The MDNC precursors were synthesized by a simple one-step self-polymerization in a water-in-oil system. And then, the obtained MDNC nanocrystalline composites can accelerate electron conduction and improve the electrocatalytic property of the tri-iodide reduction reaction (IRR) owing to the C carrier obtained through the pyrolysis process and the N-doped of α-MoC 1- x by the carbonization of dopamine and the high temperature nitrogen atmosphere. In addition, the distinct hierarchical structure of MDNC with well-developed porosity and high specific surface area can expose numerous active catalytic sites. The DSSCs using the MDNC series as CEs for I 3 −/I− exhibit power conversion efficiencies (PCE) of 5.99 %, 6.35 %, 6.57 % and 5.57 %, respectively, which were versus 5.83 % of Pt CE. [Display omitted] • Uniformed hierarchical α-MoC 1- x @N-doped carbon (MDNC) composites were prepared. • The MDNC composites all exhibited a waxberry-like morphology and effective N-doped. • The prepared MDNC (850 °C) composites existed high conductivity and rich active sites. • The DSSCs with MDNC (850 °C) CEs achieved the highest PCE of 6.57 %. [ABSTRACT FROM AUTHOR]

Vanadium-based nitrides have been applied as Pt-free counter electrodes (CEs) electro-catalysts for dye-sensitized solar cells (DSSCs) due to inexpensive cost and easy doping and modification. Herein, polyoxovanadate (NH 4) 2 V 6 O 16 assisted by melamine to prepare VN@C composites by five different synthesis routes, including solvothermal, sol–gel, hydrothermal, ball milling, and chemical mixing method. And then, five VN@C composites were assembled as CEs in the encapsulated DSSCs, and yielded power conversion efficiencies of 4.47, 5.04, 5.35, 5.49 and 6.11% for regenerate traditional I 3 −/I− shuttles by the photocurrent-photovoltage (J - V) test, respectively. The catalytic performances of VN@C composites CEs were assessed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization experiments, and the significant effects of different synthetic routes were confirmed. The results revealed that VN@C composite CEs prepared by chemical mixing method had higher catalytic performance in DSSCs, which is due to the improvement of conductivity and the high concentration of active sites. [ABSTRACT FROM AUTHOR]

Abstract Carbon molecular sieve is introduced as flexible supercapacitor electrode for the first time. The carbon molecular sieve electrode generates a specific capacitance of 108.0 F·g−1 and demonstrates an excellent stability with 98.5% preservation of its initial capacitance after 10,000 charging-discharging cycles. To further enhance the electrochemical performance, a flexible 3-D structured composite electrode is synthesized via an electrochemical polymerization method by depositing poly 3,4‑ethylenedioxythiophene film on the carbon molecular sieve surface, denoted as carbon molecular sieve@poly 3,4‑ethylenedioxythiophene. The specific capacitance of the composite electrode is up to 126.0 F·g−1, higher than both poly 3,4‑ethylenedioxythiophene (115.7 F·g−1) and carbon molecular sieve (108.0 F·g−1). Moreover, the flexible composite electrode preserves 96.0% of its initial capacitance after 10,000 charging-discharging cycles at 1.00 A·g−1. The superior performance of the composite electrode is attributed to the combined merits of the superior conductivity and excellent cycle stability of the carbon molecular sieve and 3-D porous network configuration of the poly 3,4‑ethylenedioxythiophene. [ABSTRACT FROM AUTHOR]

The photovoltaic performance of the dye-sensitized solar cell is enhanced remarkably through using magnetic counter electrode. This kind of counter electrode catalyst is a core-shell structured paramagnetic carbon sphere using carbon as shell and paramagnetic Fe 3 O 4 as core. After analyzing the catalytic behaviors of carbon sphere, Fe 3 O 4 , and paramagnetic carbon sphere on nonmagnetic and magnetic substrates toward the cobalt complex redox couple, it is proved that the internal magnetic field is conducive to both charge transfer and the mass transport processes in the electrode/electrolyte interfaces. The dye-sensitized solar cell using the magnetic carbon sphere counter electrode on magnetic substrate yields a power conversion efficiency of 10.71%, much higher than those using magnetic carbon sphere counter electrode on conductive glass (8.74%), carbon sphere counter electrode on magnetic substrate (8.50%), and Fe 3 O 4 counter electrode on magnetic substrate (6.86%). [ABSTRACT FROM AUTHOR]

A composite (Pt/CS) catalyst produced by homogeneously depositing Pt nanoparticles on a carbon spheres (CS) surface is synthesized by a simple method. A large-scale, highly effective, and flexible counter electrode is further fabricated with this composite catalyst on an ITO-PEN substrate for dye-sensitized solar cells (DSCs). As inferred from cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization curves results, this flexible Pt/CS counter electrode exhibits higher catalytic activity toward Co 3+/2+ redox couple regeneration than Pt and CS counter electrodes. The supercatalytic behavior of Pt/CS can essentially be attributed to the low apparent activation energy ( E a ) of the redox reaction between Co 3+ and Co 2+ . Using the Pt/CS counter electrode, a high power conversion efficiency (PCE) of 9.02% is achieved with a small DSCs (16 mm 2 ), and the largescale device (360 mm 2 ) generates a PCE of 6.26% under 100 mW cm −2 of simulated sunlight illumination. [ABSTRACT FROM AUTHOR]

Exploring Pt–free counter electrode catalysts for quasi–solid–state DSCs (QSDSCs) is significant for overcoming the high cost of Pt counter electrodes and their insufficient contact with the electrolyte. Herein, a two–dimensional (2D) layered MXene, V 2 C, is synthesized via a simple etching method as a counter electrode in QSDSCs. The impact of the etching time on the catalytic activity toward the regeneration of the I–/I 3 – redox couple in a quasi–solid–state electrolyte is investigated. After optimization, the V 2 C etched for 48 h shows a high catalytic activity caused by the constructed unique 2D lamellar structure, which can provide smooth diffusion channels for the penetration of the quasi–solid–state electrolyte to form sufficient contact between the V 2 C counter electrode and the electrolyte. As a result, the QSDSCs using the 2D layered V 2 C counter electrode generate a power conversion efficiency (PCE) of 7.48%. Moreover, the catalytic behavior of V 2 C is further improved by K+ intercalation, and the PCE value of the corresponding QSDSCs is enhanced to 8.30% under standard illumination (1.0 Sun) and to 10.19% under weak illumination (0.1 Sun). Meanwhile, the K+–intercalated V 2 C shows excellent stability, and 87.9% of the initial PCE of the device is retained after 1050 h in a durability test. This research is expected to provide meaningful support for the exploration of new counter electrode materials and the improvement of the contact between the counter electrode and quasi–solid–state electrolyte for the pursuit of high–performance and low–cost QSDSCs. [ABSTRACT FROM AUTHOR]

Carbon materials are potential counter electrodes for all−inorganic hole transport layer (HTL)−free perovskite solar cells (PSCs), whereas the defects of the perovskite/carbon back interface are the dominant reason for the low power conversion efficiency (PCE) of this kind of device. To resolve this problem, carbon nanofiber (CNF) was first synthesized using electrospinning technique to construct a carbon counter electrode with porous network architecture by self−supporting nature of CNF. The CsPbBr 3 based all−inorganic HTL−free PSCs using the porous CNF counter electrode shows a PCE of 5.01%. To further modify the CsPbBr 3 /carbon back interface and energy level alignment, mesoporous CNF (m−CNF) and B doped m−CNF (m−BCNF) are synthesized, which can improve the conductivity of the carbon counter electrodes as well as decline the trap state densities and accelerate the carrier extraction and transport properties of the back interface. Accordingly, the all inorganic HTL−free PSCs using m−CNF and m−BCNF counter electrodes generate high PCE of 7.48% and 8.38%, with outstanding long−tern stability. The enhanced PCE improvements can be ascribe to strategies of construction of multilevel network and B doping which can modify the CsPbBr 3 /carbon back interface, optimize the energy level alignment of the device, and enhance the conductivity of the carbon counter electrode. This research is expected to provide meaningful support for development of new counter electrode materials and back interface engineering for high-performance all inorganic HTL−free PSCs. [Display omitted] [ABSTRACT FROM AUTHOR]

To improve the catalytic activity of Nb 2 O 5 , a composite Nb 2 O 5 /C (Nb 2 O 5 imbedded in carbon support) is synthesized with a simple in situ method and then introduced the composite into dye-sensitized solar cells (DSCs) as a counter electrode (CE) catalyst. Based on the analysis of the cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel-polarization curve measurements, the catalytic activity of the Nb 2 O 5 /C composite for the regeneration of iodide-free redox couples of polysulfide (T 2 /T − ) and cobalt complex (Co 3+/2+ ) is indeed enhanced significantly as compared with pure Nb 2 O 5 , because the composite electrode eliminates the particle aggregation and forms a mesoporous network structure with large pore size. The T 2 /T − electrolyte based DSCs with Nb 2 O 5 /C CE yields a high power conversion efficiency (PCE) of 6.11%, generating a great improvement of 63.8% as compared to the Pt CE based DSCs. In addition, the Nb 2 O 5 /C exhibits higher catalytic activity than Pt for regenerating the Co 3+/2+ redox couple and the DSCs using Nb 2 O 5 /C CE shows a high PCE of 9.86%. [ABSTRACT FROM AUTHOR]

Pt/carbon fiber composite (Pt/Cf) with a low Pt loading of 1.0 wt% is introduced into dye-sensitized solar cells as counter electrode (CE) catalyst. The cobalt-electrolyte based device using this composite CE achieves power conversion efficiency of 8.97%, a great improvement of 40.4% as compared to the Cf CE based device. This research provides a feasible route to reduce the dosage of Pt in DSCs system, benefiting for the commercial application of DSCs. [ABSTRACT FROM AUTHOR]

The counter electrodes (CEs) as the basic components of dye-sensitized solar cells (DSSCs) mainly use Pt-based catalysts. It is still an urgent need to decrease the assembled cost of DSSCs by designing high-performance and low-cost Pt-free materials to replace the scarce and expensive Pt as CEs catalyst. How particularly striking are that specific precursors were prepared by ball-grinding with polyoxotungstate (H 3 PW 12 O 40) as metal source and melamine (C 3 N 3 (NH 2) 3) as carbon source and nitrogen source, and then the pyrolysis process of precursors were dynamically controlled along the temperature gradient to make the auxiliary groups leave, so as to obtain the expected N-doped W 2 C catalytic materials. Herein, four kinds of N-doped W 2 C materials have derived from polyoxotungstate precursors at the pyrolysis temperatures of 700, 800, 900 and 1000 °C, and further applied to assemble CEs catalysts in DSSCs. The high power conversion efficiencies (PCE) of 6.10, 7.01, 5.95 and 5.34% were obtained for the regeneration of traditional iodide/triiodide (I 3 −/I−), respectively. The enhanced performance of N-doped W 2 C materials can be attributed to the larger number of catalytic active sites, which was due to the higher specific surface area provided by pyrolysis and carbonization of organic complex precursor, and the activation and modification of materials by the N-doped and the high temperature. [Display omitted] • N-Doped W 2 C derived from the pyrolyzed precursors of H 3 PW 12 O 40 with C 3 N 3 (NH 2) 3. • There is the highest PCE of 7.01% of N-Doped W 2 C (obtained at 800 °C) as CEs in DSSC. •N-Doped W 2 C materials are a prospective alternative of Pt-free CEs in DSSCs. [ABSTRACT FROM AUTHOR]

• The prepared NMC, BMC, and Pt/NMC behave better than MC in DSCs as counter electrode. • The quasi-solid DSCs using Pt/NMC counter electrode showed a high PCE of 8.15%. • The liquid DSCs with Pt/NMC counter electrode gave a high PCE of 9.92% under 0.1 Sun. In this study, nitrogen-doped mesoporous carbon (NMC) and boron-doped mesoporous carbon (BMC) are synthesized and used as Pt-free counter electrode (CE) materials for dye-sensitized solar cells (DSCs). The optimized NMC and BMC CEs exhibit significantly higher catalytic activities than the pristine mesoporous carbon (MC). The I-/I 3 - in acetonitrile liquid electrolyte-based DSCs have power conversion efficiencies (PCE) of 7.20% with the NMC CE and 7.15% with the BMC CE, which are significantly higher than that obtained using the MC CE (5.88%). This is attributed to the improved effective catalytic active sites and the enhanced electrical conductivities of the NMC and BMC CEs. When Pt with trace amounts (0.1 wt%) is loaded on NMC, the liquid DSCs using Pt/NMC composite CEs yield PCE values of 8.31% and 9.92%, respectively, under 1.0 Sun and 0.1 Sun illumination. The Pt/NMC CE is further employed in quasi-solid DSCs, which also give a high PCE of 8.15% under 1.0 Sun illumination. A flexible Pt/NMC CE is also prepared on indium tin oxide-polyethylene naphthalate (ITO-PEN) substrate, and the generated liquid DSCs show a PCE of 6.92%. This work provides a feasible path to enhance the catalytic activity of the MC CE in DSCs. [ABSTRACT FROM AUTHOR]

In the present study, two typical 2D layered MXenes, i.e., Titanium carbide (Ti 3 C 2) and Vanadium carbide (V 2 C) are synthesized via a simple etching method under lower temperature as counter electrode catalysts to achieve the iodide redox couple regeneration in dye-sensitized solar cells. As indicated from the result, Ti 3 C 2 significantly outperforms V 2 C, and the device by exploiting Ti 3 C 2 counter electrode achieves power conversion efficiency (PCE) of 5.3%, while the device by applying V 2 C counter electrode only exhibits a poor PCE of 4.0%. To improve the catalytic activity of the prepared Ti 3 C 2 , the effect of etching time on the catalytic activity has been evaluated, which demonstrates that Ti 3 C 2 etched 24 h exhibits the highest catalytic activity, and the device generates a PCE of 6.2%. Lastly, the catalytic activity of the Ti 3 C 2 is further improved by postprocessing with KOH aqueous solutions, and the PCE value is up-regulated to 7.1%. The high catalytic behavior of Ti 3 C 2 could be attributed to the prominent charge transfer and mass transport properties caused by the specific 2D layer structure, suggesting a potential candidate to the noble metal electrodes. [ABSTRACT FROM AUTHOR]