Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO2 Nanorod Arrays as Electron Transfer Layer

Nanoscale Research Letters, Jan 2017

In this paper, N-doped TiO2 (N-TiO2) nanorod arrays were synthesized with hydrothermal method, and perovskite solar cells were fabricated using them as electron transfer layer. The solar cell performance was optimized by changing the N doping contents. The power conversion efficiency of solar cells based on N-TiO2 with the N doping content of 1% (N/Ti, atomic ratio) has been achieved 11.1%, which was 14.7% higher than that of solar cells based on un-doped TiO2. To get an insight into the improvement, some investigations were performed. The structure was examined with X-ray powder diffraction (XRD), and morphology was examined by scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) and Tauc plot spectra indicated the incorporation of N in TiO2 nanorods. Absorption spectra showed higher absorption of visible light for N-TiO2 than un-doped TiO2. The N doping reduced the energy band gap from 3.03 to 2.74 eV. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra displayed the faster electron transfer from perovskite layer to N-TiO2 than to un-doped TiO2. Electrochemical impedance spectroscopy (EIS) showed the smaller resistance of device based on N-TiO2 than that on un-doped TiO2.

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Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO2 Nanorod Arrays as Electron Transfer Layer

Zhang et al. Nanoscale Research Letters Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO Nanorod 2 Arrays as Electron Transfer Layer Zhen-Long Zhang 1 Jun-Feng Li 1 Xiao-Li Wang 1 Jian-Qiang Qin 1 Wen-Jia Shi 1 Yue-Feng Liu 1 Hui-Ping Gao 1 Yan-Li Mao 0 1 0 Institute for Computational Materials Science, Henan University , Kaifeng 475004 , China 1 School of Physics and Electronics, Henan University , Kaifeng 475004 , China In this paper, N-doped TiO2 (N-TiO2) nanorod arrays were synthesized with hydrothermal method, and perovskite solar cells were fabricated using them as electron transfer layer. The solar cell performance was optimized by changing the N doping contents. The power conversion efficiency of solar cells based on N-TiO2 with the N doping content of 1% (N/Ti, atomic ratio) has been achieved 11.1%, which was 14.7% higher than that of solar cells based on un-doped TiO2. To get an insight into the improvement, some investigations were performed. The structure was examined with X-ray powder diffraction (XRD), and morphology was examined by scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) and Tauc plot spectra indicated the incorporation of N in TiO2 nanorods. Absorption spectra showed higher absorption of visible light for N-TiO2 than un-doped TiO2. The N doping reduced the energy band gap from 3.03 to 2.74 eV. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra displayed the faster electron transfer from perovskite layer to N-TiO2 than to un-doped TiO2. Electrochemical impedance spectroscopy (EIS) showed the smaller resistance of device based on N-TiO2 than that on un-doped TiO2. Enhancement of efficiency; N-doped TiO2 nanorod arrays; Electron transfer layer - Background In recent years, extensive studies are focused on perovskite solar cells (PSCs) due to their outstanding properties, such as large absorption coefficient, electron-hole diffusion length, and high charge carrier mobility [1–5]. The power conversion efficiency (PCE) of perovskite solar cells has been over 22% [6]. Conventionally, perovskite solar cells consist of a perovskite layer sandwiched between an electron transfer material (ETM) layer and a hole transfer material (HTM) layer. Mesoporous TiO2 has been used as the ETM in most of the perovskite solar cells [7, 8]. Compared with the mesoporous structure, one dimensional (1D) nanostructure has some advantages, such as easy pore filling of active layer or HTM, better electron transfer, and lower charge recombination [9, 10]. Therefore, TiO2 nanorods (NRs) have been widely applied to perovskite solar cells [11, 12]. However, there are a mass of oxygen vacancies defects exist in pristine TiO2 nanorods, which reduces the efficiency and stability of the perovskite solar cell [13]. In order to solve the issues, some methods have been adopted, such as metal doping [14, 15] and nonmetal doping [16]. It has been reported that N-doped TiO2 as a photoanode of dye-sensitized solar cells (DSSCs) can improve the energy conversion efficiency due to the change of properties of TiO2, such as electron lifetime prolongation, charge transfer resistance reduction, and visible light absorption extension [17, 18]. We wondered about the effect of N-doped TiO2 on the performance of perovskite solar cells. Hence, in the present study, we synthesized N-doped TiO2 (NTiO2) nanorod arrays with hydrothermal method and fabricated perovskite solar cells using them as electron transfer layer. The solar cell performance was optimized by changing the N doping contents. The PCE of solar cells based on N-TiO2 with the N © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. doping content of 1% (N/Ti, atomic ratio) has been achieved 11.1%, which was 14.7% higher than that of solar cells based on un-doped TiO2. The possible mechanisms of enhancement were discussed based on some investigations. Methods Growth of TiO2 Nanorod Arrays Patterned fluorine-doped tin oxide (FTO)-coated glass substrate was cleaned by sonication for 20 min in detergent, acetone, 2-propanol, and ethanol, respectively. A TiO2 compact layer was deposited by dipping the substrate in a 0.2 M TiCl4 aqueous solution at 70 °C for 30 min. TiO2 NRs were grown on the treated FTO substrate by a hydrothermal method in our previous report [19]. A 0.7 mL of titanium(IV) n-butoxide was added to a mixture of hydrochloric acid and deionized water. Subsequently, the pre-calculated amount of CO(NH2)2 was added to the solution (the nominal N/Ti atomic ratio, 0.5, 1, 2, and 3%) and stirred until it was completely dissolved. T (...truncated)


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Zhen-Long Zhang, Jun-Feng Li, Xiao-Li Wang, Jian-Qiang Qin, Wen-Jia Shi, Yue-Feng Liu, Hui-Ping Gao, Yan-Li Mao. Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO2 Nanorod Arrays as Electron Transfer Layer, Nanoscale Research Letters, 2017, pp. 43, Volume 12, Issue 1, DOI: 10.1186/s11671-016-1811-0