Effects of Porosity and Amount of Surface Hydroxyl Groups of a Porous TiO2 Layer on the Performance of a CH3NH3PbI3 Perovskite Photovoltaic Cell

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• 作者：Hasyiya Karimah Adli ; Takashi Harada ; Wilman Septina ; Shuji Hozan ; Seigo Ito ; Shigeru Ikeda
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：October 1, 2015
• 年：2015
• 卷：119
• 期：39
• 页码：22304-22309
• 全文大小：363K
• ISSN：1932-7455

文摘

The structural and physicochemcal properties of a porous titanium oxide layer (pTiO₂) in CH₃NH₃PbI₃ perovskite photovoltaic cells were systematically investigated by Raman spectroscopy, nitrogen sorption, and temperature desorption spectroscopy analyses. When the heat treatment temperature (T_pTO) during the fabrication of pTiO₂ was changed from 400 to 700 掳C, its porosity and amount of surface hydroxyl groups were varied without alteration of the crystalline structure (anatase). Power conversion efficiencies (PCEs) of solar cells based on pTiO₂ prepared at different temperatures showed a volcanic-like pattern depending on T_pTO of pTiO₂; the highest PCE was obtained by using pTiO₂ prepared at T_pTO of 550 掳C. Structural analyses of the CH₃NH₃PbI₃ perovskite part performed by X-ray diffraction indicated that formation of CH₃NH₃PbI₃ perovskite was inhibited by the presence of a large amount of surface hydroxyl groups on pTiO₂ prepared at relatively low T_pTO (<550 掳C). On the other hand, significant reduction of porosity of pTiO₂ occurred when pTiO₂ was prepared at relatively high T_pTO (>550 掳C) because of extinction of micropores and sintering between the TiO₂ particles; such a structural alteration hindered the penetration of CH₃NH₃I into the pore channel of TiO₂ filled by PbI₂, resulting in a large amount of PbI₂ remaining in the finally obtained photovoltaic cell. Hence, the optimum T_pTO (550 掳C) for fabrication of pTiO₂ should be determined by its porous nature and sufficient removal of surface hydroxyl groups.