Brookite TiO2 Nanoparticle Bridge Boosts the Stability of Perovskite Solar Cells
Md. Shahiduzzaman a c, Ashish Kulkarni g, Masahiro Nakano b, Makoto Karakawa a b, Kohshin Takahashi b, Shinjiro Umezu f, Atsushi Masuda a, Satoru Iwamori c e, Masao Isomura e, Koji Tomita d, Tsutomu Miyasaka g, Tetsuya Taima a b
a Nanomaterials Research Institute (NanoMaRi), Kanazawa University
b Graduate School of Natural Science and Technology, Kanazawa University
c Research Institute of Science and Technology, Tokai University
d Department of Chemistry, School of Science, Tokai University
e Graduate School of Engineering, Tokai University
f Department of Modern Mechanical Engineering, Waseda University
g Graduate School of Engineering, Toin University of Yokohama, Kurogane-cho 1614, Aoba-ku, Yokohama, 225-8503
Poster, Md. Shahiduzzaman, 067
Publication date: 14th October 2019

Titanium dioxide (TiO2) based planar perovskite solar cells (PSCs) suffers from poor long-term stability and hysteretic behavior in the device characteristic curve. In addition to the bulk exceptional properties of perovskite, the performance and stability are also highly dependent on the conduction band energy, conductivity, and electronic trap states of TiO2 compact layer (CL). In this work, single-phase brookite (BK) TiO2 nanoparticles (NPs), synthesized via hydrothermal method by water-soluble titanium complex, is incorporated as a bridge between perovskite and TiO2 CL. This resulted in uniform large perovskite grain growth with enhanced crystallinity, significant reduction in trap/defect sites and interfacial recombination as revealed by scanning electron microscope (SEM), photoluminescence (PL), and impedance spectroscopy results respectively. The resulting PSCs show highly reproducible power conversion efficiencies (PCEs) up to ~18.2% (vs. ~15%) with stable performance of 18% under continuous light illumination (1 Sun) at maximum power point tracking (MPPT) in contrast to only TiO2 CL based planar devices. In addition, to support the MPPT (stability) results, light soaking test was performed by exposing the non-encapsulated BK TiO2 NPs based-device for ~2 hr. under continuous light illumination (1 Sun) in air with high humidity (in a range of 60-70%). This result showed that the devices retained 88% of its initial efficiency after light soaking test. To the best of our knowledge, this is so far the best photo-stability data reported for brookite NPs based PSCs. Furthermore, we further measured the moisture stability of the PSCs with and without a BK TiO2 NP layer before and after storing in the dark (without sealing or encapsulation). The PCE of the TiO2 CL/BK-TiO2 NPs based perovskite device degraded by just 16% after dark storage for 47 days. The stability is mainly improved by the high-quality perovskite film obtained on highly conductive crystalline and particularly high stable BK TiO2 NPs itself. Therefore, the remarkable long-term stability of the TiO2 Cl/BK-TiO2-based perovskite devices is probably conferred by the high potential of the BK TiO2 NPs. Based on our present study, at the end; we provide further direction to enhance the stability of planar PSCs.This work will advance an alternative approach to anatase TiO2-based PSCs applications, and their photovoltaic device performance and preservation stability were enhanced.

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