| In this dissertation, we focus on the synthesis, regulation and applications of organics in dye-sensitized solar cells and perovskite solar cells. In order to further reduce their costs and improve their optical power efficiences and stability. The main contents in thisdissertation are summarized as follows:Bis(imidazolium) iodides are highly advantageous in lower price and volatility compared to the tradional lithium iodide. Three types of bis(imidazolium) iodides compounds, namely 1,1'-methylene bis(3-imidazolium) diiodide (MIDI), 1,1'-methylene bis(3-n-methylimidazolium) diiodide (MMIDI), and 1,1'-methylene-bis(3-n-ethylimidazolium) diiodide (MEIDI) were synthesized respectively. They were used to replace the traditional iodide sources (lithium iodide) in the electrolytes. Dye-sensitized solar cells (DSSC) based on theses electrolytes are constructed. The impacts of imidazolium cations with different substituents (sizes of alkyl chains) on the electrochemical behaviors of the I3-/I-electrolytes were investigated. The MEIDI with the largest alkyl chains leads to longest electron lifetimes and best open-voltage (Voc) for the reason of electrostatic interactions between solvated Im+and charge carriers become stronger with larger alkyl chains, and it is more difficult for imidazolium iodides to flow into photoelectrode, thus decreasing the recombination between the electron on TiO2 conduction band and the I3-in the electrolyte. Meanwhile the MIDI with the smallest alkyls shows highest short-circuit photocurrent (Jsc) for higher catalytic activity of electrode toward the I-/13- redox couple. Considering the Rct of DSSCs with different bis(imidazolium) iodides, the device with electrolyte based MIDI gains great power conversion efficiency (PCE,5.05%).Fluorecent perylene with excellent fluorescent property is added into the liquid electrolyte in dye-sensitized solar cells. The perylene exhibited a great down-shifting ability, and could convert almost all of the short wavelength photons (350-440 nm) to longer wavelengths ones (450-550 nm), fortunately photons with the wavelength of 450-550 nm can be more efficiently utilized by the whole DSSC system than that of 350-440 nm. In consideration of down-shifting ability of perylene, dye increases the light utilization indirectly. Under optimal perylene concentration (0.05 M), solar cells based on this electrolyte exhibited an 11.6% improvement in performance compared with solar cells based on traditional electrolyte without perylene.We have designed a novel hole-conductor-free and insulating layer free mesoscopic perovskite solar cells (PSCs) with a low cost carbon counter electrode (CE). This structure eliminates the insulating layer leading to enhances charge transportation. At the same time, this structure improves the stability of the constructed PSCs. In order to further enhance the light harvesting capability, a mixture of methylammonium (CH3NH3+, MA) and formamidinium (HN=CHNH3+, FA) perovskite material is explored. With the introduction of FA cation into the methylammonium lead iodide perovskite (MAPbI3), the obtained perovskites exhibit tetragonal structure, while lattice constant increases with higher FA amount. The optical band gap of the mixed (FA)x(MA)1-xPbI3 is lowered compared with pure MAPbI3, thus more light can be absorbed. At the same time, Cubic:Column composite structure of (FA)x(MA)1-xPbI3 was formed on the top of mesoscopic TiO2. This nanostructure not only leads to fully coverage of perovskite on TiO2 but also provides salutary electron transport channels to effectively reduce the electron recombination probability. As a result, optimal solar cell efficiency of 13.03% of (FA)x(MA)1-x Pbl3 composite structure based PSC (when x is fixed at 0.25) was achieved, higher than that of PSC based typical MAPbI3 cuboids. Despite of the improved efficiency, the Cubic:Column composite structure caused by the addition of FAI also contributes to higher long-term and thermal stability... |
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