The University of Tokyo
Carbon nanotube films and graphene for perovskite solar cells
Department of Mechanical Engineering, The University of Tokyo, Tokyo 113-8656, Japan
Energy NanoEngineering Laboratory, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8564, Japan
A film of single-walled carbon nanotubes (SWNTs) can be a dual-functional layer as electron-blocking-layer and transparent-conductive electrode in various solar cells. Here, this dual functional applications of SWNT film and graphene are demonstrated for organic-inorganic hybridperovskite solar cells. Replacement of ITO in inverted-type perovskite solar cells, SWNTs/PEDOT:PSS/CH3NH3PbI3/PCBM/Al, is demonstrated by adjusting the surface energy of PEDOT:PSS . The flexible application on polyethylene terephthalate (PET) is also demonstrated . Furthermore, replacement of electron-blocking-layer and metal electrode in normal-type perovskite solar cells is demonstrated as well. They show high power conversion efficiency (PCE), cost-efficiency, and higher stability. Those devices can have comparable PCE as the conventional design withorganic electron-blocking layer and top metal electrode. In addition to the expected lower cost and improved stability, these solar cells can be potentially semi-transparent when transparent SWNT films are used. This means that they can be illuminated from either cathode or anode side. The normal-type perovskite solar cell, composed of ITO/TiO2/CH3NH3PbI3/SWNTs, can achieve a PCE of 10% without doping of SWNTs . The PCE can be as high as 17 % with the preliminary doping of the film of SWNTs using Spiro-MeOTAD, which is the typical electron-blocking-layer used for the normal type perovskite solar cells. The PMMA layer on top of the film of SWNTs can also contribute as doping and protection layer. Furthermore, the modified structure with a perovskite layer sandwiched by C60 and SWNTs, i.e. ITO/C60/CH3NH3PbI3/SWNTs, can lead to the solar cells without hysteresis and with much improved air-stability . The effective passivation of the degradation of perovskite material by moisture can be achieved with C60 and SWNTs . This device showabout 13 % PCE without hole-transporting layer and 17% with spiro-MeOTAD this far . This can be a good candidate for scale-up demonstration of practical perovskite solar cells.
This work was supported by JSPS KAKENHI Grant Numbers JP25107002, JP15H05760, and IRENA Project by JST-EC DG RTD, Strategic International Collaborative Research Program, SICORP. Part of this work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
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I received Ph.D. in School of Engineering from the University of Tokyo in 1988. I worked as a research associate until 1991, as a lecturer for a year, as an associate professor from 1993, as a full professor from 2004, and as a distinguished professor from 2014 at the University of Tokyo. From April 2015, I also work as a cross-appointment fellow for Advanced Industrial science and technology (AIST). I was awarded a Guest Professor position in Peking University from November 2016. I joined Professor Richard Smalley group at Rice University as visiting fellow for about 2 years during 1989 through 1991. During this period, I started to study chemical physics of clusters, fullerenes, and carbon nanotubes. Later, I invented the new CVD technique of SWNTs from low pressure alcohol in 2002, so-called Alcohol Catalytic CVD (ACCVD). Current research topics are growth, optical characterization, thermal characterization and solar cell application of carbon nanotubes and graphene. I have served as program officer of Japan Society for the Promotion of Science (JSPS) during 2009-2012, and as the president of “The Fullerenes, Nanotubes and Graphene Research Society,” since 2011. Since 2016, I serve as the co-chair of steering committee of 'International Conference on Science and Application of Nanotubes and Low-Dimensional Materials (NT series)'.I also served as Director of The Japan Society of Applied Physicsin 2014 and as Executive Director in 2015. I am an Editor of "Nanoscale and Microscale Thermophysical Engineering," and an associate editor of “Int. J. Heat Mass Transfer.” I have published more than 210 ISI-listed papers which have been cited more than 8,200 times, resulting the h-index of 49 (Google Scholar shows 13,700 citations and h-index 61).