Ruiyuan Hu

Foldable Hole-Transporting Materials for Merging Electronic States between Defective and Perfect Perovskite Sites

Keith Gregory Brooks, Paul Joseph Dyson, Ruiyuan Hu, Hiroyuki Kanda, Mohammad Khaja Nazeeruddin, Kasparas Rakstys, Jianxing Xia, Yi Zhang

Defective and perfect sites naturally exist within electronic semiconductors, and considerable efforts to reduce defects to improve the performance of electronic devices, especially in hybrid organic-inorganic perovskites (ABX(3)), are undertaken. Herein, foldable hole-transporting materials (HTMs) are developed, and they extend the wavefunctions of A-site cations of perovskite, which, as hybridized electronic states, link the trap states (defective site) and valence band edge (perfect site) between the naturally defective and perfect sites of the perovskite surface, finally converting the discrete trap states of the perovskite as the continuous valence band to reduce trap recombination. Tailoring the foldability of the HTMs tunes the wavefunctions between defective and perfect surface sites, allowing the power conversion efficiency of a small cell to reach 23.22% and that of a mini-module (6.5 x 7 cm, active area = 30.24 cm(2)) to reach as high as 21.71% with a fill factor of 81%, the highest value reported for non-spiro-OMeTAD-based perovskite solar modules.

WILEY-V C H VERLAG GMBH2023

Novel photoelectric material of perovskite-like (CH3)(3)SPbI3 nanorod arrays with high stability

Ruiyuan Hu, Xin Li, Wei Liu, Mohammad Khaja Nazeeruddin, Shanshan Xiao

Organometallic halide perovskite materials make great achievements in optoelectronic fields, especially in solar cells, in which the organic cations contain amine components. However, the amine with N-H bonds is easily hydrolyzed with moisture in the air, weakening the perovskite materials stability. It is desirable to develop other non-amine stable perovskite materials. In this work, sulfur-based perovskite-like (CH3)(3)SPbI3 nanorod arrays were fabricated by a solution-processed method, which can be indexed hexagonal crystal structure in the space group P63mc. The binding force is exceptionally strong between the non-amine (CH3)(3)S+ and PbI6 octahedral, leading to high stability of (CH3)(3)SPbI3. The (CH3)(3)SPbI3 nanorod arrays can keep the morphology and crystal structure in an ambient atmosphere over 60 days. In addition, the (CH3)(3)SPbI3 nanorod arrays can offer direct charge transfer channels, which show excellent optoelectronic properties. The (CH3)(3)SPbI3 nanorod arrays-based solar cells with VOx hole transfer layers achieved a power conversion efficiency of 2.07% with negligible hysteresis. And the (CH3)(3)SPbI3 nanorod arrays were also effectively applied in photodetectors with interdigitated gold electrodes. This work demonstrates that sulfur-based perovskite-like (CH3)(3)SPbI3 is a novel promising stable compound with great potential for practical optoelectronic applications. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

2021

Enhanced stability of alpha-phase FAPbI(3) perovskite solar cells by insertion of 2D (PEA)(2)PbI4 nanosheets

Ruiyuan Hu, Xin Li, Mohammad Khaja Nazeeruddin, Sanghyun Paek, Yi Zhang

Methylammonium (MA) is one of the main obstacles that hold back the commercialization of perovskite solar cells (PSCs). Formamidinium (FA)-based perovskite is a promising photovoltaic material due to its higher thermal stability and smaller bandgap. However, despite the introduction of Cs+ in FAPbI(3), the photoactive alpha-phase FAPbI(3) can quickly transform into a non-perovskite hexagonal phase delta-FAPbI(3), which limits its use in perovskite solar cells. In this work, we show that the dispersion of 2D (PEA)(2)PbI4 nanosheets into a Cs(0.1)FA(0.9)PbI(3) thin film successfully prevents the transformation of the alpha-phase Cs(0.1)FA(0.9)PbI(3) to the delta-phase. Because of the 2D (PEA)(2)PbI4 nanosheets, a higher quality perovskite thin-film was obtained with a longer carrier lifetime, lower trap state density, and enhanced stability. The resulting device achieves a high power conversion efficiency of 20.44%, which is one of the highest for MA-free perovskites and retains 82% of its initial efficiency after 800 h of aging study.

2020

Stable and High-Efficiency Methylammonium-Free Perovskite Solar Cells

Ruiyuan Hu, Wen Luo, Mohammad Khaja Nazeeruddin, Yi Zhang, Bing Zhang

Organic-inorganic metal halide perovskite solar cells (PSCs) have achieved certified power conversion efficiency (PCE) of 25.2% with complex compositional and bandgap engineering. However, the thermal instability of methylammonium (MA) cation can cause the degradation of the perovskite film, remaining a risk for the long-term stability of the devices. Herein, a unique method is demonstrated to fabricate highly phase-stable perovskite film without MA by introducing cesium chloride (CsCl) in the double cation (Cs, formamidinium) perovskite precursor. Moreover, due to the suboptimal bandgap of bromide (Br-), the amount of Br- is regulated, leading to high power conversion efficiency. As a result, MA-free perovskite solar cells achieve remarkable long-term stability and a PCE of 20.50%, which is one of the best results for MA-free PSCs. Moreover, the unencapsulated device retains about 80% of the original efficiencies after a 1000 h aging study. These results provide a feasible approach to enhance solar cell stability and performance simultaneously, paving the way for commercializing PSCs.

2020

The Synergism of DMSO and Diethyl Ether for Highly Reproducible and Efficient MA(0.5)FA(0.5)PbI(3)Perovskite Solar Cells

Keith Gregory Brooks, Min Chen, Ruiyuan Hu, Hiroyuki Kanda, Yonghui Lee, Mohammad Khaja Nazeeruddin, Yi Zhang

Composition and film quality of perovskite are crucial for the further improvement of perovskite solar cells (PSCs), including efficiency, reproducibility, and stability. Here, it is demonstrated that by simply mixing 50% of formamidinium (FA(+)) into methylammonium lead iodide (MAPbI(3)), a highly crystalline, stable phase, and compact, polycrystalline grain morphology perovskite is formed by using a solvent-mediated phase transformation process via the synergism of dimethyl sulfoxide and diethyl ether, which shows long carrier lifetime, low trap state density, and a record certified 21.8% power conversion efficiency (PCE) in pure-iodide, alkaline-metal-free MA(0.5)FA(0.5)PbI(3)perovskite-based PSCs. These PSCs show very high operational stability, with 85% PCE retention upon 1000 h 1 Sun intensity illumination. A 17.33% PCE module (6.5 x 7 cm(2)) is also demonstrated, attesting to the scalability of such devices.

2020