5 research outputs found

    Tuning the HOMO and LUMO Energy Levels of Organic Dyes with <i>N</i>‑Carboxomethylpyridinium as Acceptor To Optimize the Efficiency of Dye-Sensitized Solar Cells

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    Different from traditional D−π–A sensitizers (the traditional design concept of the organic dyes is the donor−π-linker–acceptor structure), a series of organic dyes with pyridinium as acceptor have been synthesized in order to approach the optimal energy level composition in the TiO<sub>2</sub>–dye–iodide/triiodide system in the dye-sensitized solar cells. HOMO and LUMO energy level tuning is achieved by varying the conjugation units and the donating ability of the donor part. Detailed investigation on the relationship between the dye structure and photophysical, photoelectrochemical properties and performance of DSSCs is described. For TPA-based dyes, by substituting the 3-hexylthiophene group with a carbon–carbon double bond as π-spacer, the bathochromic shift of absorption spectra and higher current density (<i>J</i><sub><i>sc</i></sub>) are achieved. When the methoxyl and <i>n</i>-hexoxyl are introduced into <b>CM301</b> to construct dyes <b>CM302</b> and <b>CM303</b>, the absorption peak is red-shifted compared with that of <b>CM301</b> due to the increase of the electron-donating ability. The devices fabricated with sensitizers <b>CM302</b> and <b>CM303</b> show higher <i>J</i><sub><i>sc</i></sub> and open-circuit voltage (<i>V</i><sub><i>oc</i></sub>) than those of the device sensitized by <b>CM301</b>, which can be mainly attributed to the wider incident photon-to-current conversion efficiency (IPCE) response and the suppression of electron recombination between TiO<sub>2</sub> film and electrolyte, respectively. The effects of different electron donors in DSSCs application are compared, and the results show that sensitizers with a phenothiazine (PTZ) electron-donating unit give a promising efficiency, which is even better than the TPA-based dyes. This is because the PTZ unit displayed a stronger electron-donating ability than the TPA unit (oxidation potential of 0.82 and 1.08 V vs the normal hydrogen electrode (NHE), respectively). For sensitizers <b>CM306</b> and <b>CM307</b>, the introduction of 1,3- bis­(hexyloxy)­phenyl increases the donating ability of the donor part. Furthermore, the presence of long alkyl chains decreases the dye adsorption amount on the TiO<sub>2</sub> surface, which diminishes dye aggregation and the electron recombination effectively, though, with less adsorption amount of dyes on TiO<sub>2</sub>, the device sensitized by dye <b>CM307</b> obtained the best conversion efficiency of 7.1% (<i>J</i><sub><i>sc</i></sub> = 13.6 mA·cm<sup>–2</sup>, <i>V</i><sub><i>oc</i></sub> = 710 mV, <i>FF</i> = 73.6%) under AM 1.5G irradiation (100 mW·cm<sup>–2</sup>)

    Efficient Panchromatic Organic Sensitizers with Dihydrothiazole Derivative as π‑Bridge for Dye-Sensitized Solar Cells

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    Novel organic dyes <b>CC201</b> and <b>CC202</b> with dihydrothiazole derivative as π-bridge have been synthesizedand applied in the DSSCs. With the synergy electron-withdrawing of dihydrothiazole and cyanoacrylic acid, these two novel dyes <b>CC201</b> and <b>CC202</b> show excellent response in the region of 500–800 nm. An efficiency as high as 6.1% was obtained for the device fabricated by sensitizer <b>CC202</b> together with cobalt electrolyte under standard light illumination (AM 1.5G, 100 mW cm<sup>–2</sup>). These two novel D-π-A panchromatic organic dyes gave relatively high efficiencies except common reported squaraine dyes

    Structure Engineering of Hole–Conductor Free Perovskite-Based Solar Cells with Low-Temperature-Processed Commercial Carbon Paste As Cathode

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    Low-temperature-processed (100 °C) carbon paste was developed as counter electrode material in hole–conductor free perovskite/TiO<sub>2</sub> heterojunction solar cells to substitute noble metallic materials. Under optimized conditions, an impressive PCE value of 8.31% has been achieved with this carbon counter electrode fabricated by doctor-blading technique. Electrochemical impedance spectroscopy demonstrates good charge transport characteristics of low-temperature-processed carbon counter electrode. Moreover, this carbon counter electrode-based perovskite solar cell exhibits good stability over 800 h

    Novel Small Molecular Materials Based on Phenoxazine Core Unit for Efficient Bulk Heterojunction Organic Solar Cells and Perovskite Solar Cells

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    Two novel Acceptor-Donor-Acceptor (A-D-A) structured small molecular (SM-) materials <b>POZ2</b> and <b>POZ3</b> using an electron-rich phenoxazine (POZ) unit as a core building block were designed and synthesized. Their unique characteristics, such as suitable energy levels, strong optical absorption in the visible region, high hole mobility, and high conductivity, prompted us to use them both as p-type donor materials (DMs) in SM-bulk heterojunction organic solar cells (BHJ OSCs) and as hole transport materials (HTMs) in CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>-based perovskite solar cells (PSCs). The <b>POZ2</b>-based devices yielded promising power conversion efficiencies (PCEs) of 7.44% and 12.8% in BHJ OSCs and PSCs, respectively, which were higher than the PCEs of 6.73% (BHJ-OSCs) and 11.5% (PSCs) obtained with the <b>POZ3</b>-based devices. Moreover, our results demonstrated that the <b>POZ2</b> employing the electron-deficient benzothiazole (BTZ) as linker exhibited higher hole mobility and conductivity than that of the <b>POZ3</b> using thiophene as linker, leading to better device performance both in BHJ-OSCs and PSCs. These results also provide guidance for the molecular design of high charge carrier mobility SM-materials for highly efficient BHJ OSCs and PSCs in the future

    Highly Efficient Integrated Perovskite Solar Cells Containing a Small Molecule-PC<sub>70</sub>BM Bulk Heterojunction Layer with an Extended Photovoltaic Response Up to 900 nm

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    We demonstrate a high efficiency perovskite solar cell (PSC) integrated with a bulk heterojunction layer, based on acceptor–donor–acceptor (A–D–A) type hole transport material (HTM) and PC<sub>70</sub>BM composite, yielding improved photoresponse. Two A–D–A-structured hole transporting materials termed <b>M3</b> and <b>M4</b> were designed and synthesized. Applied as HTMs in PSCs, power conversion efficiencies (PCEs) of 14.8% and 12.3% were obtained with <b>M3</b> and <b>M4</b>, respectively. The HTMs <b>M3</b> and <b>M4</b> show competitive absorption, but do not contribute to photocurrent, resulting in low current density. This issue was solved by mixing the HTMs with PC<sub>70</sub>BM to form a bulk heterojunction (BHJ) layer and integrating this layer into the PSC as hole transport layer (HTL). Through careful interface optimization, the (FAPbI<sub>3</sub>)<sub>0.85</sub>­(MAPbBr<sub>3</sub>)<sub>0.15</sub>/HTM:PC<sub>70</sub>BM integrated devices showed improved efficiencies of 16.2% and 15.0%, respectively. More importantly, the incident-photon-to-current conversion efficiency (IPCE) spectrum shows that the photoresponse is extended to 900 nm by integrating the <b>M4</b>:PC<sub>70</sub>BM based BHJ and (FAPbI<sub>3</sub>)<sub>0.85</sub>­(MAPbBr<sub>3</sub>)<sub>0.15</sub> layers
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