| Mesoscopic solar cell (MSC) is a representative of the third generation solar cell. Compared to other kinds of photovoltaic devices, the solar cell with mesoscopic structure possesses larger specific surface area, helping to capture more photon and assisting photo induced carrier seperation.Dye-sensitized solar cell (DSSC) is one typical mesoscopic solar cell. Commonly, they employ mosoporous TiO2nanocrystalline as the photoelectrode. This kind of photoelectrode has a large specific surface area upto285m2/g, which is780times larger than the planar photoelectrode. Up to now, the highest certified photoelectric conversional efficiency (PCE) of the DSSC and perovskite solar cell are11.9%and20.1%, respectively, which is comparable to that of the troditional Si version. Moreover, the cost of MSC is much lower and the fabricating process is much easier, making MSC possess larger application potential.Usually, MSC employ Pt or Au as counter electrode to collect hole. Although the cost of MSC is lower than the Si-based solar cell, the noble mental is still an issue for further decreasing the price of MSC. The rise of a cheap carbon counter electrode makes MSC really low-cost photovoltaic devices. At present, TiO2/ZrO2/Carbon structured mesoscopic solar cell has become a modish research object, which provides promising perspective of industrial application.In this paper, we developed and supermolecular cations or organic sulfide electrolyte, and also employed interfacial modification method in mesoscopic solar cell to obtain improvement of performance. Moreover, the impedance measurements and analysis were introduced and developed to provide theoretical support for the mesoscopic solar cell working principles. The main contents of this paper include:We prepared a novel iodine free electrolyte by combining the supermolecular cations with organic sulfide redox. The cations were designed according to the coordination effect between alkali metal cations with crown ethers. This design removes the Hoffmann degradation and breaks the solubility limit. As a result, the devices stability was significantly improved and after optimization, the PCE of mesoscopic DSSC based on the Li-crown reached6.6%. In addition, the function of supermolecular cations was revealed that the electron recombination was suppressed and the energy level was better aligned.We introduced a si lane monolayer to modify the surface of TiO2in the TiO2/ZrO2/Carbon structured perovskite mesoscopic solar cell. This monolayer was self assembled between TiO2and the perovskite forming covalence bonding with TiO2and hydrogen bonding with perovskite. The recombination process was restrained and the built-in potential was enhanced, and also the mesoscopic surface was modified to obtain better contact and crystallization. The average PCE was therefore improved from9.6%to11.7%, indicating that the self assembled silane monolayer is a simple but useful method to improve the device performance.We introduced impedance measurements and analysis to study the working principles of TiO2/ZrO2/Carbon structured perovskite mesoscopic solar cell. The specific arc in high frequency region corresponding to the carbon/perovskite contact was firstly observed, and the main function of the other two layers TiO2and ZrO2were revealed. After all, proper electrochemical circuit model was established for fitting the Nyquist plot. This work opens up a path to interpretate the impedance spectra of mesoscopic perovskite solar cell, and provides theoretical support for studying the working principles, indicating that impedance is a valuable diagnostic method for characterized perovskite mesoscopic solar cell. |
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