| Energy means more and more to human being with the development of science and technology and the quality of our future life depends on availability of energy source. In twenty-first century, the depletion of fossil fuel has been foreseen and solar energy is attracting more and more attention due to its huge source, environmental friendly and highly sustainable. Among them, a new type of photovoltaic device, converting the solar energy to electric energy, is developing at an astonishing speed. Compared with conventional PN junction solar cell, these devices employ three-dimensional interpenetrating network junctions for light harvesting whereas the majority holes and electrons are present in each of the two phases, which will enhance the light collection efficiency and reduce the recombination rate. The pores of these three-dimensional porous material are in the2-50nm size range, which are belong to mesopores category. Therefore, this type of photovoltaic is named mesoscopic solar cell.Employing mesoscopic structure to collect photons was first reported by Gratzel and O’Regan in dye sensitized solar cell (DSSC) in1991. Mesoscopic solar cell can be produced with low-cost and simple processes, which compare favorably with conventional PN junction solar cell. However, most of the reported mesoscopic solar cells, especially all solid-state devices, employ noble metal as counter electrode (CE), which has become the biggest obstacle for its commercialization.Herein, we introduce the low-cost carbon materials for all solid-state DSSC instead of noble metal CE, where the structure and manufacturing process have been improved. The carbon layer and ZrO2insulating layer are studied in varied approaches to obtain the optimum performance. At the hole transport material/counter electrode (HTM/CE) interface, charge transport and charge injection are improved by p-type doping process with Lewis acid. The carbon CE is also applied in the emerging TiO2/perovskite heterojunction mesoscopic solar cell where the highly ordered mesoporous carbon is employed to obtain the better photovoltaic performance. The main work of this paper is as follows: The structure and manufacturing process of all solid-state carbon CE based DSSC are illustrated, where the porous contact form between CE and HTM has been proved to better than flat contact form. Then, we studied the effect of carbon layer thickness on the pore filling, charge injection, recombination and final performance. The different ratios of carbon paste have also prepared to investigate the influence on electrical property, pore feature and final efficiency.The ZrO2layer has been investigated as both insulating layer and scattering layer. HTM pore filling status is observed in all solid-state carbon CE based DSSC with nanoparticle ZrO2layer. Then, the ZrO2thickness and particle size is optimized, which are found to affect the light harvesting, charge transfer and recombination process.On the basis of high contact area between CE and HTM, Lewis acid SnCl4is employed as p-type dopant in spiro-OMeTAD to enhance the conductivity and adjust energy level. The UV-vis and photoluminescence results demonstrate that SnCl4has strong ability to oxidize spiro-OMeTAD and form charge transfer complex, which show higher doping efficiency than commonly used LiTFSI. Moreover, the photovoltaic device with SnCl4doping also presents higher FF and power conversion efficiency.Highly ordered mesoporous (OMC) carbon with well-connected frameworks was applied in perovskite/TiO2heterojunction mesoscopic solar cells as CE, where the meso concept extends from photoanode to CE. The OMC were synthesized by a solvent evaporation induced self-assembly method, which is commercially available for its nontoxic, low-cost and simple fabrication process. Compared with previous carbon black, the photovoltaic devices contain OMC present lower charge transfer resistance and higher power conversion efficiency,... |
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