Highly Efficient Organic Sensitizers for Solid-State Dye-Sensitized Solar Cells (original) (raw)
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Advanced Energy Materials, 2014
suffer from potential leakage problems associated with the volatile nature of the liquid electrolyte, limiting this technology for large-scale applications. [ 3 ] In an effort to address these issues, a p-type organic semiconductor termed 2,2′,7,7′-tetrakis-(N,N-dip -methoxyphenyl-amine)9,9′ spirobifl uorene (Spiro-OMeTAD) was developed to replace the liquid electrolyte as a redox couple in the fabrication of "solid-state" dye-sensitized solar cells (ssDSCs) by Bach et al. in 1998. [ 4 ] To date, the highest effi ciency of 7.2% for ssDSCs have been achieved using Spiro-OMeTAD as the hole transport material (HTM), which was reported by Nazeeruddin and co-workers. [ 5 ] Recently, Snaith and co-workers employed an organometallic halide perovskite with Spiro-OMeTAD as HTM obtained a record effi ciency of 15.4%. [ 6 ] However, previous studies have demonstrated that the low hole mobility and conductivity of Spiro-OMeTAD signifi cantly limits the device performance near the maximum power point in solar cell. [ 7,8 ] In addition, the lengthy synthetic route of Spiro-OMeTAD may make it impractical for large-scale application in ssDSCs. [ 9 ] More importantly, the substantial overpotential required for dye A series of triphenylamine-based small molecule organic hole transport materials (HTMs) with low crystallinity and high hole mobility are systematically investigated in solid-state dye-sensitized solar cells (ssDSCs). By using the organic dye LEG4 as a photosensitizer, devices with X3 and X35 as the HTMs exhibit desirable power conversion effi ciencies (PCEs) of 5.8% and 5.5%, respectively. These values are slightly higher than the PCE of 5.4% obtained by using the state-of-the-art HTM Spiro-OMeTAD. Meanwhile, transient photovoltage decay measurement is used to gain insight into the complex infl uences of the HTMs on the performance of devices. The results demonstrate that smaller HTMs induce faster electron recombination in the devices and suggest that the size of a HTM plays a crucial role in device performance, which is reported for the fi rst time.
Dye-sensitized Solar Cells: New Approaches with Organic Solid-state Hole Conductors
CHIMIA, 2015
Solid-state dye-sensitized solar cells (sDSCs) in which a solid organic charge-transfer medium, or hole conductor (HC), is interposed between a dye-coated mesoporous oxide electrode and a conductive counter electrode, have attracted considerable interest as viable alternatives to the more ubiquitous mediator-electrolyte DSC. Of particular importance to efficient operation are, in addition to the useful processes contributing to current generation (light harvesting, electron injection and current collection), the recombinative deleterious processes. The organic HCs are highly reactive toward electrons in the oxide or the conducting glass support, therefore necessitating the inclusion of a carefully prepared thin blocking oxide underlayer support as well as the molecular design of special dark current-suppressing dyes. Initially (mid-1990s) sDSCs with organic small molecular weight hole conductors have undergone systematic investigation. At the same time the first tests of sDSCs with ...
Highly Efficient Solid-State Dye-Sensitized Solar Cells Based on Triphenylamine Dyes
Advanced Functional Materials, 2011
Two triphenylamine-based metal-free organic sensitizers, D35 with a single anchor group and M14 with two anchor groups, have been applied in dye-sensitized solar cells (DSCs) with a solid hole transporting material or liquid iodide/triiodide based electrolyte. Using the molecular hole conductor 2,2',7,7'-tetrakis-(N , N-dip -methoxyphenyl-amine)9,9'-spirobifl uorene (spiro-OMeTAD), good overall conversion effi ciencies of 4.5% for D35 and 4.4% for M14 were obtained under standard AM 1.5G illumination (100 mW cm − 2). Although M14 has a higher molar extinction coeffi cient (by ∼ 60%) and a slightly broader absorption spectrum compared to D35 , the latter performs slightly better due to longer lifetime of electrons in the TiO 2 , which can be attributed to differences in the molecular structure. In iodide/triiodide electrolyte-based DSCs, D35 outperforms M14 to a much greater extent, due to a very large increase in electron lifetime. This can be explained by both the greater blocking capability of the D35 monolayer and the smaller degree of interaction of triiodide (iodine) with D35 compared to M14. The present work gives some insight into how the molecular structure of sensitizer affects the performance in solid-state and iodide/triiodide-based DSCs.
Dye Sensitized Solar Cell: A Summary
Dye sensitized solar cell (DSSC) devices incorporating organic and inorganic materials have found a host of applications. The search for low-cost, high efficient and flexible devices has lead to a remarkable increase in the research and development of solar cell. The current review, describes the constitution components of DSSC in a detailed manner and their development and challenges are also discussed. We focused on various structural modifications in wide band gap nano-crystalline semiconductor materials for an efficient electron transfer to reduce the recombination rate. Fruitful attempts have been made to design new molecular dyes for the wide range of absorption in the visible region. Co-Sensitization is an appropriate technique to enhance the absorption range of dye molecules and to increase the efficiency of solar cell. Moreover hole transport materials, there are the efficient tool to replace redox couple based liquid electrolyte and it produce stable solid state DSSC. The successful modification of counter electrode with different morphology promotes the rate electron transfer into electrolyte. This review also covers the update technology to construct efficient, stable and flexible dye sensitized solar cell.
Novel Conjugated Organic Dyes for Efficient Dye-Sensitized Solar Cells
Advanced Functional Materials, 2005
A new metal-free sensitizer 2-[3-(4-dimethylamino-phenyl)-allylidene]-malonic acid (2) has been synthesized by the condensation of N,N'-dimethylaminocinnaldehyde and malonic acid. This dye has two carboxyl gmups on the same carbon atom, which act as better electron withdrawing groups in addition to providing effective anchoring to titanium dioxide. The new dye has characterized by UV-Vis, 'H NMR and CHN analysis. Dye-sensitized nanocrystalline-titanium dioxidesemiconductor solar cells (DSSC) have been tested in a stable and durable redox electrolyte. The efficiency of dye is as high as 1.38%. The dye molecule is thermally stable up to 100°C. TPC Code : C09B ; H0 1 L3 1/00
2012
Two donor-π-acceptor (D-π-A) dyes are synthesized for application in dyesensitized solar cells (DSSC). These D-π-A sensitizers use triphenylamine as donor, oligothiophene as both donor and π-bridge, and benzothiadiazole (BTDA)/cyanoacrylic acid as acceptor that can be anchored to the TiO 2 surface. Tuning of the optical and electrochemical properties is observed by the insertion of a phenyl ring between the BTDA and cyanoacrylic acid acceptor units. Density functional theory (DFT) calculations of these sensitizers provide further insight into the molecular geometry and the impact of the additional phenyl group on the photophysical and photovoltaic performance. These dyes are investigated as sensitizers in liquid-electrolyte-based dye-sensitized solar cells. The insertion of an additional phenyl ring shows significant influence on the solar cells' performance leading to an over 6.5 times higher efficiency (η = 8.21%) in DSSCs compared to the sensitizer without phenyl unit (η = 1.24%). Photophysical investigations reveal that the insertion of the phenyl ring blocks the back electron transfer of the charge separated state, thus slowing down recombination processes by over 5 times, while maintaining efficient electron injection from the excited dye into the TiO 2 -photoanode.