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The oxide/nitride passivation and the flip‐chip package technology are developed for the perovskite solar cells. The heat resulting from the physical vapor deposition decomposes the active perovskite layer and degrades the efficiency of the perovskite solar cells down by more than 45%. Remarkably, with Si‐nitride passivation processed by plasma‐enhanced vapor deposition, the efficiency of the perovskite solar cell only decays about 9.1%. It is because that the plasma‐enhanced vapor deposition causes much less external energy on the perovskite solar cell. Using the exponential efficiency‐decay curves of the flip‐chip packaged perovskite solar cells, the characteristic time of the reliability‐tested solar cell can be calculated to be 145.8, 390.7, and 4864 h for air‐ambient, glove chamber, and water‐ambient tests, respectively. It is concluded that the concentration of O2(g) in the reliability test ambient is the root cause for the efficiency degradation of the perovskite solar cells. The low mobility of O2(g) under the water‐ambient reliability test results in the low probability of the adsorption of O2(g) on the surface of the flip‐chip package, which is the key factor for the least efficiency degradation of the perovskite solar cells among the three reliability tests. [ABSTRACT FROM AUTHOR]

Room‐temperature‐processed TiO2 (R‐Lt‐TiO2) electron transporting layers (ETLs) possess low conductivity and connectivity, resulting in poor photovoltaic performance. Herein, an ethanol (EtOH)‐soluble, highly conducting fullerene derivative, C60RT6, was used as an additive for Lt‐TiO2 ETLs. Room‐temperature processed nanocomposite ETL (R‐Fu/Lt‐TiO2) is prepared simply by spin coating a C60RT6 and G‐TiO2 NPs (TiO2 nanoparticle prepared by grinding the bulk TiO2 powder) mixture. R‐Fu/Lt‐TiO2 has better aligned with the frontier orbitals of the FAxMA1−xPbI3, better continuity, conductivity, flatness, and higher surface hydrophilicity compared to Lt‐TiO2 ETL. Perovskite films spin coated on R‐Fu/Lt‐TiO2 ETLs also have slightly larger grains and thickness compared to those deposited on Lt‐TiO2. Perovskite solar cells (PSCs) based on a R‐Fu/Lt‐TiO2 ETL possess higher power conversion efficiency (PCE, up to 20% on glass substrate), less (negligible) current hysteresis, and better long‐term stability compared to those using R‐Lt‐TiO2 as an ETL. The flexible PSC (used indium tin oxide/polyethylene terephthalate (ITO/PET) as a substrate) with a R‐Fu/Lt‐TiO2 ETL achieves a PCE of 18.06% and retains 90% of the initial PCE after 500 bending cycles with a bending radius of 6 mm. The PCE of the flexible cell with a Lt‐TiO2 ETL is only 8.2%, and loses 60% of the initial value after 500 bending cycles. [ABSTRACT FROM AUTHOR]

The sequential deposition of a NiOx hole‐transporting layer, one‐step CH3NH3PbI3 perovskite absorber, and blended electron‐transporting layer that comprises [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) and PNDI(2OD)T2 via automated ultrasonic spray‐coating technique is demonstrated in air for planar inverted p–i–n solution‐processed perovskite solar cells. Films fabricated via laboratory‐sale spin‐coating and industrially compatible spray‐coating process, respectively, are compared with each other to optimize both the film‐coating quality and corresponding device performance. This is validated by the photovoltaic performance of prototype devices with three spray‐coated layers with the active area of 1 × 1 cm2. The champion cells achieve a power conversion efficiency of 10.09%, which is one of the highest efficiencies obtained from fully spray‐processed large‐area perovskite solar cells thus far. Furthermore, these results reinforce the feasibility of the spray‐coating methodology for the fabrication of multilayers within perovskite solar cells stack and low‐cost route toward upscaling the manufacturing alternatives to spin coating. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have received great attention due to their outstanding performance and their low processing costs. To boost their performance, one approach is to reinforce the built‐in electric field (BEF) to promote oriented carrier transport. The BEF is maximized by reinforcing the work function difference between cathode and anode (Δμ1) and increasing the work function difference between lower and upper surfaces of perovskite film (Δμ2) via introduction of electric dipole molecules, denoted as PTFCN and CF3BACl. The synergistic reinforcement of BEF improves charge transport and collection, and realizes markedly high photovoltaic performances with the best power conversion efficiency (PCE) up to 21.5%, a growth of 15.6% as compared to the control device, which is higher than the superposition of improvements achieved by either raising Δμ1 or Δμ2. Importantly, dual‐functional CF3BACl not only supplies dipole effect for tuning the surface potential of perovskite but offers hydrophobic trifluoride group toward the long‐term stable unencapsulated PSCs retaining more than 95% PCE after storing 2000 h under ambient conditions. This work demonstrates the synergistic effect of Δμ1 and Δμ2, providing an effective strategy for the further development of PSC in terms of photovoltaic conversion and stability. [ABSTRACT FROM AUTHOR]

A series of small‐molecule‐based hole‐transporting materials (HTMs) featuring a 4H‐cyclopenta[2,1‐b : 3,4‐b′]dithiophene as the central core with triphenylamine‐ and carbazole‐based side groups was synthesized and evaluated for perovskite solar cells. The correlations of the chemical structure of the HTMs on the photovoltaic performance were explored through different combinations of the central π‐bridge moieties. The optical and electrochemical properties, energy levels, and hole mobility were systematically investigated, revealing the significant influence of the central core planarity and packing structure on their photovoltaic performance. The optimized device based on CT1 exhibited a PCE (power conversion efficiency) of 17.71 % with a device architecture of FTO/TiO2 compact layer/TiO2 mesoporous/CH3NH3PbI3/HTM/MoO3/Ag, which was found to be on par with that of a cell fabricated based on state‐of‐the‐art spiro‐OMeTAD (16.97 %) as HTM. Moreover, stability assessment showed an improved stability for CPDT‐based HTMs in comparison with spiro‐OMeTAD over 1300 h. Four HTMs based on cyclopenta[2,1‐b;3,4‐b′]dithiophene core are designed and applied for lead perovskite (MAPbI3) solar cells. PSCs based on CT1 as HTM afford an impressive power conversion efficiency of 17.71 %. The devices based on the CT1 presented significantly higher stability than the device based on spiro‐OMeTAD. [ABSTRACT FROM AUTHOR]

Four heterocyclic spiro-type hole transporting materials (HTMs) carrying a spiro[fluorene-9,9′-xanthene] (SFX) (SFX-TPAM and SFX-TPA) or spiro[fluorene-9,9′-thioxanthene] (SFT) unit (SFT-TPAM and SFT-TPA) were synthesized through a low-cost facile route with high yields for perovskite solar cell (PSC) applications. In terms of absorption, these four compounds in the film state are all transparent at wavelengths longer than 430 nm, which is beneficial for allowing visible light to reach the perovskite active layer without being absorbed by the hole transporting layer (HTL). The photovoltaic performance of the inverted PSCs based on these small molecular HTMs with the device architecture of glass/ITO/HTL/CH3NH3PbI3/C60/BCP/Ag was tested. Only SFX-TPAM had its highest occupied molecular orbital (HOMO) level matched with the valence band of CH3NH3PbI3. The inverted PSC based on a dopant-free SFX-TPAM HTL achieves a power conversion efficiency of 10.23% under the illumination of standard one sun lighting, which is better than that (8.17%) of the cell based on dopant-free spiro-OMeTAD. The better photovoltaic performance of SFX-TPAM compared to spiro-OMeTAD may be due to the MAPbI3 film deposited on it having better quality. These results indicate that the facilely synthesized, low-cost SFX based small molecules can be used as the HTMs for PSCs. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (H2O<0.1 ppm, O2<10 ppm). The PCE of the solar cell based on a perovskite film having the grain size larger than 1 μm ( D-10) decreases less than 10 % with storage in a glove box and less than 15 % when it was stored under an ambient atmosphere for 30 days. However, the cell using the perovskite film composed of small (∼100 nm) perovskite grains (D-0) exhibits complete loss of PCE after storage under the ambient atmosphere for only 15 days and a PCE loss of up to 70 % with storage in the glove box for 30 days. These results suggest that, even under H2O-free conditions, the chemical- and thermal-induced production of pin holes at the grain boundaries of the perovskite film could be the reason for long-term instability of inverted perovskite solar cells. [ABSTRACT FROM AUTHOR]

ABSTRACT Two D-π-A copolymers, based on the benzo[1,2- b:4,5- b′]-dithiophene (BDT) as a donor unit and benzo-quinoxaline (BQ) or pyrido-quinoxaline (PQ) analog as an acceptor (PBDT-TBQ and PBDT-TPQ), were designed and synthesized as a p-type material for bulk heterojunction (BHJ) photovoltaic cells. When compared with the PBDT-TBQ polymer, PBDT-TPQ exhibits stronger intramolecular charge transfer, showing a broad absorption coverage at the red region and narrower optical bandgap of 1.69 eV with a relatively low-lying HOMO energy level at −5.24 eV. The experimental data show that the exciton dissociation efficiency of PBDT-TPQ:PC71BM blend is better than that in the PBDT-TBQ:PC71BM blend, which can explain that the IPCE spectra of the PBDT-TPQ-based solar cell were higher than that of the PBDT-TBQ-based solar cell. The maximum efficiency of PBDT-TPQ-based device reaches 4.40% which is much higher than 2.45% of PBDT-TBQ, indicating that PQ unit is a promising electron-acceptor moiety for BHJ solar cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1822-1833 [ABSTRACT FROM AUTHOR]

Two fused-thiophene-containing ruthenium sensitizers, [Ru(Hdcbpy)(ottip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ [ Z1, H2dcbpy = 4,4′-dicarboxy-2,2′-bipyridine, ottip = 2-(5-octylthieno[3,2- b]thiophen-2-yl)-1 H-imidazo[4,5- f][1,10]phenanthroline] and [Ru(Hdcbpy)(odttip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ { Z2, odttip = 2-[6-octyldithieno(3,2- b:2′,3′)thiophen-2-yl]-1 H-imidazo[4,5- f][1,10]phenanthroline}, were designed for use in dye-sensitized solar cell (DSSC) applications. The fused-thiophene-based Z1 and Z2 have stronger light-harvesting capabilities compared with a non-fused-thiophene analog, [Ru(Hdcbpy)(otip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ [ JF-2t, otip = 2-(5-octylthiophen-2-yl)-1 H-imidazo[4,5- f][1,10]phenanthroline], and a standard N3 dye. The power-conversion efficiency of the Z1- and Z2-sensitized solar cells were superior (8.70 % and 8.15 %) to JF-2t- and N3-sensitized solar cells (7.85 and 7.40 %, respectively) under standard AM1.5G full sunlight irradiation. The photovoltaic performance of Z1 was better than Z2, primarily owing to the fact that Z1-based cells have a higher level of dye loading and less charge recombination, as seen from the electrochemical impedance spectroscopy data. This study not only demonstrates the excellent power-conversion efficiency of new fused-thiophene ruthenium sensitizers, but also points to the promise that fused-thiophene antennas might be a useful molecule in the engineering of ruthenium dyes for DSSCs. [ABSTRACT FROM AUTHOR]

A new class of hole-transport materials (HTMs) based on the bimesitylene core designed for mesoporous perovskite solar cells is introduced. Devices fabricated using two of these derivatives yield higher open-circuit voltage values than the commonly used spiro-OMeTAD. Power conversion efficiency (PCE) values of up to 12.11 % are obtained in perovskite-based devices using these new HTMs. The stability of the device made using the highest performing HTM ( P1) is improved compared with spiro-OMeTAD as evidenced through long-term stability tests over 1000 h. [ABSTRACT FROM AUTHOR]

This work presents a CHNHPbI/PCBM organic solar cell. Organic PCBM film and CHNHPbI perovskite film are deposited on the PEDOT:PSS/ITO glass substrate by the spin coating method. The performance of the organic solar cells was observed by changing the thickness of CHNHPbI perovskite. The thickness of a perovskite film can affect the carrier diffusion length in a device that strongly absorbs light in the red spectral region. The short-circuit current density and the power conversion efficiency were 21.9 mA/cm and 11.99 %, respectively, for the sample with 210-nm-thick CHNHPbI perovskite active layer. [ABSTRACT FROM AUTHOR]

Seven new donor-spacer-acceptor metal-free organic dyes containing a fluorene and/or thiophene unit as a conjugated spacer are prepared and their physicochemical properties as well as photovoltaic performance are studied. The electron transfer from donor to acceptor upon excitation of these dyes is sensitive to the conjugated spacers. If a stronger donor moiety such as (ethylenedioxy)thiophene is used as a spacer, such as in F-E1 dye, the dye molecule has a better charge separation and therefore high efficiency. Furthermore, for the same donor and acceptor, fluorene is a better conjugated spacer than the bithiophene moiety because of its nonplanar conformation, which avoids the electron-hole recombination of dye upon photoexcitation. Short molecules with planar conformation aggregate easily, and the corresponding device reveals low open-circuit voltage Voc. On the other hand, dye molecules with long alkyl side chains (large size) adsorb less on the TiO2 electrode, which results in a smaller short-circuit current density Jsc. The difference in the efficiency of these dyes is small except for F-1 (owing to its short conjugation length), and electron density difference map analyses reveal that photoexcitation transfer of electron density from the donating moieties toward the acceptor/anchoring units occurs for all molecules. The small difference in the efficiency is attributed partly to the degree of effective charge transfer upon excitation, not totally to the absorption profile of the dye molecules. Furthermore, time-dependent DFT simulated absorption spectra are in excellent agreement with experimental spectra when the dyes are in their protonated states in THF solution. The transition probability calculated with the electron density difference analyses combined with the absorption data and photovoltaic performance provide useful information for designing organic sensitizers for dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are one of the highly promising new‐generation photovoltaic technologies. One of the remaining challenges for commercializing PSCs is to prepare high‐quality, large‐area perovskite films in an ambient atmosphere reproducibly using less toxic materials. Herein, a nonvolatile, less toxic substance, 2‐pyrrolidinone (2P), is used as a complexant solvent for the perovskite precursor solution. Combining this with a newly developed spin‐assisted solvent extraction (SASE) crystallization method, a high‐quality perovskite film is prepared in air reproducibly. The nonvolatile nature of 2P and the formation of MAI–PbI2–2P adduct widen the time window for antisolvent engineering, and SASE enhances the solvent exchange rate of the precursor film to form a high‐quality perovskite film in air. An inverted cell (based on the postsolvent‐treated perovskite absorber) exhibits a power conversion efficiency of more than 18%. This film preparation method is feasible for depositing a high‐quality mixed‐cation or mixed‐cation, mixed‐halide perovskite film on both PEDOT:PSS and TiO2 surfaces to fabricate inverted and regular PSCs, respectively, to achieve efficiencies of more than 16%. More importantly, high‐quality, large‐area MAPbI3 film is prepared reproducibly in air for fabricating perovskite submodules to achieve an efficiency of 14% (verified at 13.04% after the cell is packed for efficiency evaluation). [ABSTRACT FROM AUTHOR]

From light to electricity: The inside cover picture illustrates the concept of designing hole transporting materials (HTMs) for perovskite solar cells. A subtle change of the central π‐bridge unit can lead to a significant improvement of device performance. In view of their excellent performance, the materials with two‐dimensional structural framework are promising HTMs for efficient and stable perovskite photovoltaic devices. More details can be found in the Full Paper by Yan‐Duo Lin et al. on page 307 in Issue 2, 2019 (10.1002/ente.201800939). [ABSTRACT FROM AUTHOR]

Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. [ABSTRACT FROM AUTHOR]

Comprehensive studies were carried out to explore the thickness-dependent characteristics of thermally evaporated C 60 thin films. The structural, optical, electronic and surface properties of the resultant C 60 thin films were analyzed using Raman scattering spectrometry, photoluminescence spectroscopy, absorbance spectroscopy, photoelectron emission spectrometry and water droplet contact angle measurement. The experimental results show that the thickness of the C 60 thin film has a decisive impact on the photovoltaic performance of CH 3 NH 3 PbI 3 based solar cells in terms of open-circuit voltage (V OC ), short-circuit current density (J SC ) and fill factor (FF). In the case of the 2.5 nm-thick C 60 film, the solar cells have the better V OC and J SC , as the results of the lower electron affinity and higher transparency. The FF of the solar cell is related to the coverage of C 60 on the transparent conductive electrode (TCE) and the CH 3 NH 3 PbI 3 perovskite continuity. Consequently, the photovoltaic performance can be expected to be improved by using a smooth TCE. [ABSTRACT FROM AUTHOR]

A series of alcohols (methanol, ethanol and isopropyl alcohol) were added to poly(3,4-ethylenedioxythiophene): (polystyrene sulfonate) (PEDOT: PSS) aqueous solutions in order to manipulate the molecular structure of the PEDOT chains in PEDOT: PSS hole transporting materials (HTMs) and thus to improve the power conversion efficiency of CH 3 NH 3 PbI 3 based solar cells. The structural and electronic characteristics of the resultant PEDOT: PSS HTMs were analyzed using atomic-force microscopy, contact angle measurement, Raman scattering spectrometry and photoelectron spectrometry. The properties of the PEDOT: PSS thin films could be controlled by tuning the viscosity of the PEDOT: PSS solutions. High viscosity PEDOT: PSS solutions resulted in linear structured PEDOT chains, which increased the work function of the PEDOT: PSS HTMs thereby improving the open-circuit voltage of the CH 3 NH 3 PbI 3 solar cells. The surface roughness and surface free energy of the PEDOT: PSS HTMs influence the structural properties of CH 3 NH 3 PbI 3 thin films, which determines the exciton dissociation at the CH 3 NH 3 PbI 3 /PEDOT: PSS interface (short-circuit current density) and the carrier recombination at the CH 3 NH 3 PbI 3 /[6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) interface (fill factor). In addition, it is predicted that the power conversion efficiency can be further improved by increasing the crystallinity of the CH 3 NH 3 PbI 3 thin film. [ABSTRACT FROM AUTHOR]

A series of nonpolar antisolvents (chlorobenzene, bromobenzene, iodobenzene and toluene) were used to assist in the formation of smooth and crystalline CH 3 NH 3 PbI 3 thin films by a one-step spin-coating method. The structural, optical and excitonic characteristics of the resultant CH 3 NH 3 PI 3 thin films were analyzed using an atomic-force microscope, X-ray diffractometer, absorbance spectrum, photoluminescence (PL) spectrum, time-resolved PL and temperature-dependent PL. The properties of the CH 3 NH 3 PbI 3 thin films are dependent on the relative polarity and boiling point of the nonpolar antisolvents used in the washing treatment process. The interplay between nucleation (relative polarity) and crystal growth (boiling point) during the formation of CH 3 NH 3 PbI 3 thin films influences the short-circuit current density (J SC ) and power conversion efficiency (PCE) of the corresponding solar cells. The experimental results demonstrate that iodobenzene can be substituted for toluene as a more efficient antisolvent in the washing treatment process during the fabrication of CH 3 NH 3 PbI 3 thin films. In addition, it is predicted that the J SC and PCE can be further improved by increasing the crystallinity of the CH 3 NH 3 PbI 3 thin film. [ABSTRACT FROM AUTHOR]

Inverted-type perovskite solar cells offer the potential of fabrication by low-temperature solution processing as an alternative to conventional-type perovskite solar cells. PEDOT:PSS is commonly used as the hole transport layer (HTL), but its acidic nature may damage the reliability and stability of the photovoltaic device. In this study, we demonstrate the use of MoO x and WO x HTLs as an alternative to PEDOT:PSS for planar CH 3 NH 3 PbI 3 perovskite solar cells. Furthermore, the MoO x and WO x HTLs are treated using a UV-ozone treatment to improve the surface coverage of the perovskite layer. The resultant conversion efficiency (PCE) for the best cells at AM1.5G illumination with a shadow mask was 13.1%. [ABSTRACT FROM AUTHOR]

This work studies annealing effects of the CH 3 NH 3 PbI 3 perovskite film for solar cell applications by time-resolved photoluminescence (TR-PL) spectra. The different thermal annealing temperatures process influences the quality and exciton lifetime of the CH 3 NH 3 PbI 3 perovskite film and importantly the device performance. The CH 3 NH 3 PbI 3 perovskite film of the optimal thermal annealing temperatures (100 °C) would significantly extended exciton lifetime and yield a higher open-circuit voltage, with short-circuit current density ( J SC ) = 21.58 mA/cm 2 , open-circuit voltage ( V OC ) = 0.84 V, fill factor (FF) = 61.4%, and η = 11.12%, respectively. [ABSTRACT FROM AUTHOR]

Raman spectroscopy and photoluminescence (PL) were used to investigate the improved short-circuit current density ( J SC ) of CdS/CdSe quantum dot (QD)-sensitized solar cells with multi-walled carbon nanotubes (MWCNTs). Raman and PL experiments were carried out in order to explore the hot-electron and cold-electron injections, respectively. The experimental results showed that the concentration of MWCNTs influences the hot-electron and cold-electron injections from CdS/CdSe QDs to TiO 2 nanoparticles. Therefore, the improved J SC in CdS/CdSe QD-sensitized solar cells can be explained as due to the better electron injections. [ABSTRACT FROM AUTHOR]

• First demonstration of III-V solar cells embedded in miniaturized smart dusts. • Only ∼40 % cell area (0.4 cm2) required compared with the Silicon counterparts. • Continuous wave operation under a solar incidence angle of 0°–75°. • Cells allow self-sustaining operation of dust modules without battery charging. • Develop an Application for wireless communication with dusts through smartphones. The functioning of self-sustaining smart dust modules plays a vital role in the development of the smart electric grid. In this work, we first devise a flexible triple-junction III-V solar cell embedded inside a smart dust module suitable for outdoor applications. These flexible solar cells are demonstrated to have a bending radius of over 5 cm and exhibit a conversion efficiency of around 25% under air mass 1.5G (1 sun) conditions. Under normal incidence of sunlight at the same conditions, our cell with its small active area of 0.4 cm2 can generate around 10.1 mW of electrical power. This is sufficient to meet the direct current power consumption (∼5.4 mW) requirements of our dust module, which includes a temperature/moisture sensor, a 3-axis linear accelerometer, and a Bluetooth chip. In comparison to a silicon-based flexible solar cell, our demonstrated III-V solar cell is smaller, requiring approximately 40% of the area to produce the same electrical power output. Our dust module is controlled using a self-developed Android application installed on a smartphone and can sustain continuous-wave operation for data collection and wireless transmission even when the incident angle of the sunlight reaches 75°. Pulse-mode operation is still possible even in the case of nearly 90° illuminations (for example, at sunset). Overall, the measurement results for this flexible solar cell are promising, allowing for further reduction in the size of a self-sustaining smart dust module with improved reliability. These advantages could facilitate development of the next generation of energy saving smart electric grids. [ABSTRACT FROM AUTHOR]

Abstract: A novel, heteroleptic ruthenium dye comprising a vinyl group between the carboxylate and bipyridine segments as well as extended π-conjugation of the ancillary ligand, employing alkyl-bithiophene, was synthesized. The dye displayed a remarkably high absorption coefficient of 2.51 × 104 M−1 cm−1 (at 562 nm) for its metal-to-ligand charge transfer band. The photo-to-current conversion efficiency of the corresponding dye-sensitized solar cell was 9.12% under AM 1.5 (100 mW/cm2) irradiation. Furthermore, owing to both the very strong metal-to-ligand charge transfer band and the large number of dye molecules adsorbed on the TiO2 electrode, the conversion efficiency of the dye-sensitized cell was >7.5% at a light intensity ≤198 mW cm−2. [Copyright &y& Elsevier]

Abstract: In this study, the photoelectrochemical characteristics of a ruthenium photosensitizer with an alkyl bithiophene group, designated as CYC-B1, are studied. The effect of mesoporous TiO2 film thickness on the photovoltaic performance of CYC-B1 and N3 dye-sensitized solar cells was investigated. The performance of the dye-sensitized nanocrystalline TiO2 solar cells (DSSC) fabricated using CYC-B1 dye-anchored TiO2 photoelectrode showed a convincing enhancement in cell efficiency when the TiO2 film thickness was increased from 3μm (eff.=5.41%) to 6μm (eff.=7.19%). The efficiency of the CYC-B1-sensitized DSSC was maximum at 6μm of the TiO2 film thickness, reached its limiting value and remained constant up to 53μm, although a similar trend was also observed for N3 dye-sensitized DSSC, however, the maximum efficiency achieved was only at 27μm thickness (eff.=6.75%). As expected, the photocurrent density generated in the DSSC modified by CYC-B1 dye is larger than that from N3 dye. The effect of guanidinium thiocyanate (GuSCN) (additive) addition to the electrolyte on the photovoltaic performance of DSSCs based on CYC-B1 was also investigated. Furthermore, the electrochemical impedance spectroscopy (EIS) technique and photo-transient laser method have been employed to analyze the charge transfer resistances (R ct) and the lifetime of the injected electrons on the TiO2 containing different thicknesses. [Copyright &y& Elsevier]