报告题目： Perovskite Hybrid Solar Cells and Our High Performance Development
报告人： Prof. Tsutomu Miyasaka
工作单位：Toin University of Yokohama, Graduate School of Engineering
报告时间： 2016年11月7日上午9：00 -10:00（星期一）
报告地点： 物理楼333讲学厅
报告人简介：
Tsutomu Miyasaka received his Ph.D. degree in engineering from The University of Tokyo in 1981, and joined Fuji Photo Film, Co. where he conducted R&Ds on high sensitivity photographic materials, lithium-ion secondary batteries, and design of an artificial photoreceptor, all of which were based on electrochemistry and photochemistry. In 2001, he joined Toin University of Yokohama (TUY), Japan, Graduate School of Engineering, to continue photoelectrochemistry. From 2006 to 2009 he was dean of the Graduate School. From 2005 to 2010, he served as guest professor at The University of Tokyo. Main topic of his research has been design of solution-printable and lightweight flexible photovoltaic (PV) cells. In 2004 he established a TUY-based company, Peccell Technologies and served as CEO till 2009. Since the discovery of organic inorganic perovskite as PV absorber in 2006, he has focused his research on the organo lead halide perovskite PV cells, both for analysis of optoelectronic properties and design of high performance solar cell. He was a recipient of Ministry of Science & Education award on his achievements of green sustainable solar cell technology in 2009. Lecturing and publishing widely, he has directed R&D teams of national research programs, NEDO and JST, on dye-sensitized and hybrid solar cells.
  注：宮坂力（Miyasaka Tsutomu）教授是国际公认的钙钛矿太阳能电池（Perovskite solar cells)研究的奠基人，其开创性工作“Organometal halide perovskites as visible-light sensitizers for photovoltaic cells”A. Kojima, K. Teshima, Y. Shirai, and T. Miyasaka, J. Am. Chem. Soc., 2009, 131, 6050-6051.迄今为止已经被单篇引用了2000多次。
Abstract
  Organo metal halide perovskites are photosensitive ionic crystals exhibiting diverse functions in optoelectronics. At the same time, they are characterized as narrow bandgap semiconductors having high photoconductivity in photocurrent generation (Fig. 1). Lead halide perovskite, represented by CH3NH3PbX3 (X=Br, I), strongly absorbs visible light with extinction coefficient as high as 105 cm-1 (1~2 orders larger than Si). It exhibits superior performance in photovoltaic power conversion as well as high sensitivity in photon-mode detection of visible light. This ionic semiconductor is soluble to polar solvent that enables various solution processes for electrode fabrication. In 2006, we fabricated the first photovoltaic (PV) cell using this perovskite as a sensitizer on mesoporous TiO2 and obtained power conversion efficiencies (PCE) as high as 2.2 % in junction of liquid redox electrolytes.1a In 2008, this method was immediately applied to create a first full solid-state perovskite-based PV cell by using carbon-polymer conductive composite as a hole transport material.1b In the following 7 years, rapid progress in PCE by improving the quality and stability of perovskite crystal layers has enabled PCE to reach 22%. Our group showed the cell fabrication in ambient air conditions to achieve >17% by simple one-step solution process.2 We have also investigated the origin of hysteretic current-voltage (I-V) behavior, characteristic to this hybrid material. Origin of hysteresis can be due to ionic migration and/or ferroelectric polarization of the crystal being caused by external bias. But large hysteresis is mostly the result of structure defect at hetero-junction interfaces that depends on selection of carrier transport materials. The practical influence of hystesis on stability of cell operated under light was recently investigated.3
  Beside organic and carbonaceous carrier transfer materials, various inorganic metal oxide materials were found to be useful not only for supplying physically robust carrier collectors but also for serving as good scaffold in nucleation of perovskite crystal. Al2O3 is especially interesting in its role in blocking recombination as insulator to enhance photovoltage.2,4 Low temperature printing process (<120oC) can be applied to metal oxide layers. Good photovoltaic performance with high voltage is obtained by using ZnO, SnO2, brookite TiO2 and their composites as mesoporous electron collectors. ZnO/SnO2 composites exhibit good PCE over 15% and long cell life (> months) without encapsulation.5 Brookite TiO2 is especially unique in terms of strong interparticle necking by dehydration condensation reaction that enables formation of dense uniform layer. Thin plastic film-based flexible perovskite device was fabricated. With non-hysteretic PCE>13% it shows stable performance against mechanical bending over 100 times (Fig. 2).6 Recently, triple cation (MA, FA, Cs)-based perovskite is highlighted as a highly stable and high efficiency material. We have also fabricated this mixed halide perovskite, Csx(FAPbI3)0.83(MAPbBr3)0.17, which showed >20% PCE. Especially a device fully made by low temperature process (<150oC) achieves 20.5% PCE and high Voc of 1.15V.
  Enormous potential of perovskite-based device is not only for power devices but also for high performance optical sensing. Such additional but equally notable functions of CH3NH3PbI3 are also enabled by strong light absorption and activity of long-lived photocarriers for high yield quantum conversion. As a photodiode, gain of CH3NH3PbI3-induced photocurrent was found to reach a level of the order of 103, showing excellent light-switching performance.2,7 Such rare functions of the perovskite as a hybrid semiconductor material provide a lot of rooms for us to explore in photovoltaics and optoelectronics.
REFERENCES
[1] a) A. Kojima, T. Miyasaka, et al. 2007, Abstract #352, 212th ECS Meeting, Washington, USA, October 2007; b) ibid. PRiME 2008, Abstract #27, Honolulu, Hawaii, October 2008.
[2] T. Miyasaka, Chem. Lett. 2015, 44, 720-729.
[3] A. K. Jena, A. Kulkarni, M. Ikegami, T. Miyasaka, J. Power Sources, 2016, 309, 1-10.
[4] M. M. Lee, J. Teuscher, T. Miyasaka, T. N. Murakami, H. J. Snaith, Science, 2012, 338, 643-647
[5] J. Song, E. Zheng, X.-F. Wang, W. Tian, T. Miyasaka, Solar Ener. Mat. Solar Cells, 2016, 144, 623-630.
[6] A. Kogo, M. Ikegami, T. Miyasaka, submitted.
