2, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico
Mesoporous structure perovskite solar cell (MS PSCs) is constructed by front contact, electron selective contact and metal back contact [1,2]. For this configuration the mesoporous structure plays an important role, due to its porosity, pore size and morphology can determine the coverage, morphology of the perovskite layer and carrier lifetime [3,4]. One of the most used mesoporous materials for this application has been the titanium dioxide, for itself shows excellent properties such as chemical and biological stability, optical transparency, low toxicity and inexpensive production. This work presents the fabrication of the mesoporous titanium dioxide (mp-TiO2) applied as a scaffold layers on perovskite solar cells. We developed two different synthesis of mp-TiO2 by changing the templates and the acidity in a way to study the dispersion of the particles and the final mesoporosity obtained. The first synthesis was composed by titanium isopropoxide (TTIP), acetic acid (CH3COOH), polyvinylpyrrolidone (PVP) and ethanol (C2H6O). The second synthesis was obtained by adding titanium isopropoxide (TTIP), hydrochloric acid (HCl), Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly (ethylene glycol) (P-123) and ethanol (C2H6O). The two different mp-TiO2 precursor solutions were spin-coated at different speeds onto previous prepared blocking layer of TiO2 (bl-TiO2, 30 nm) deposited on FTO substrates. The obtained layers (FTO/bl-TiO2/mp-TiO2) were thermally treated at different temperatures to induce the crystallinity. After that a layer of perovskite was deposited by spin coating, followed by spin-coating of Spiro-OMeTAD as hole transport materials (HTL). We studied the volume porosity obtained by using the Volume Average Theory. The porosities obtained were from 40-44% when the spin speed is varied. The best power efficiency (PCE) obtained was about 13% with Spiro-OMeTAD.
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3)Y. Zhao, K. Zhu. The journal of Physical Chemistry Letter 4 (2013) 2880-2884.
4)S. Li, Y. Wang, C. Tsai, C. Wen, C. Yu, Y. Yang, J. Lin, D. Wang, C. Chen, Y. Yeha, C. Chen. Nanoscale y (2015) 14532-14537.