1:30pm - 2:00pmInvited
The Future of Photovoltaics
University of California, Berkeley, United States
In the last few years, PV electricity became cost-competitive with electricity produced by oil-fired power plants, new nuclear power plants and diesel generators. Global PV production capacity will double within the next five years to 100-120 GWp/a, bringing PV installations into the Terawatt range. The now starting, and quickly accelerating transformation of our energy system to efficient use of ultimately 100% renewable energy is a disruptive process, whose wide-spread impact can hardly be overestimated.
A key factor for this growth will be continuous technology advances aimed at higher efficiencies at reduced cost. In addition, for many applications such as solar rooftops in densely populated areas such as Singapore cell efficiency will be even more important than lowest cost, to optimize the energy harvest from a given area.
Crystalline Silicon technology currently represents 90% of the global PV market. This well-known technology will still allow many technological advances to be introduced in the coming years, aimed at higher efficiencies at reasonable cost. However, this development is approaching a glas ceiling of 29% efficiency for any given single-bandgap semiconductor material. New approaches for higher efficiencies require heterojunctions, and several approaches will be discussed, including heterojunctions on silicon that allow to combine well-established large-scale Silicon PV technology with new technologies, such as low-cost III/V or Perovskite layers.
2:00pm - 2:30pmInvited
Lead-Free Organic-Inorganic Perovskite Halides
University of Cambridge, United Kingdom
Hybrid organic-inorganic perovskites are found in a number of families, particularly the halides (e.g. CH3NH3PbI3) and formates (e.g. [(CH3)2NH2]Zn(HCOO)3) . The talk will focus on the halides, which are attracting a great deal of attention on account of their excellent performance as active layers in photovoltaic cells and LEDs. Our work in this area has explored the use of Tolerance Factors to rationalise known structures and predict new ones . We have also examined the role of hydrogen bonding in hybrid perovskite halides , as well as their mechanical properties . Our on-going research focuses on the search for lead-free hybrid perovskites, including layered bismuth-containing phases  and hybrid double perovskites such as (CH3NH3)2KBiCl6 , (CH3NH3)2TlBiBr6 and (CH3NH3)2AgBiBr6.
 W. Li, Z. M. Wang, F. Deschler, S. Gao, R. H. Friend and A. K. Cheetham, Nature Reviews Materials 2, 16099 (2017)
 G. Kieslich, S. Sun and A. K. Cheetham, Chem. Sci. 5, 4712 (2014); Chem. Sci. 6, 3430 (2015)
 J.-H. Lee, N. C. Bristowe, P. D. Bristowe, and A. K. Cheetham Chem. Comm. 51, 6434 (2015); J.-H. Lee et al, Chem. Mater. 28, 4259 (2016)
 S. Sun, Y. Fang, G. Kieslich, T. J. White & A. K. Cheetham, J. Mater. Chem. A 3, 18450 (2015)
 S. Sun, S. Tominaka, J.-H. Lee, S. F. Xie, P. D. Bristowe & A. K. Cheetham, APL Mater. 4, 031101 (2016)
 F. Wei et al, Materials Horizons 3, 328 (2016)
 Z. Deng, F. X. Wei, S. Sun, G. Kieslich, A. K. Cheetham & P. D. Bristowe, J. Mater. Chem. A 4, 12025 (2016)
 F. Wei et al, Chem. Mater. DOI: 10.1021/acs.chemmater.6b03944
2:30pm - 3:00pmInvited
How to Remove I-V Hysteresis in Perovskite Solar Cell
Sungkyunkwan University, South Korea
Since the first report on solid-state perovskite solar cell with power conversion efficiency (PCE) of 9.7% in 2012, intensive researches led to its PCE up to 22%. It is believed that perovskite solar cell is promising next-generation photovoltaics thanks to superb performance and very low cost. Best photovoltaic performance has been usually achieved from normal structure with mesoporous TiO2 layer. However, severe current-voltage hysteresis in mesoscopic perovskite solar cell has been issued. In this talk, a universal method to remove the I-V hysteresis in perovskite solar cell is presented. MAPbI3, FAPbI3 and mixed perovskite (FAPbI3)x(APbX3)1-x are prepared via Lewis acid-base adduct method, where a specific element is added in stoichiometric precursor solution. Compared with severe I-V hysteresis for all the perovskite films prepared from the conventional precursor solution, no hysteresis is observed for all the perovskite films by the doping approach. Moreover, hysteresis-less behavior is independent on scan rate. Opto-electronic studies along with theoretical calculation can explain the basis for such a disappearance of hysteresis in all perovskite formula.
3:00pm - 3:30pmInvited
Stable Perovskite Solar Cells by 2D/3D Interface Engineering
École Polytechnique Fédérale de Lausanne, Switzerland
Despite the impressive photovoltaic performances,perovskite solar cells are poorly stable under operation, failing by far the requirements for a widespread commercial uptake.1-3 Various technological approaches have been proposed to overcome the instability problem, which, while delivering appreciable improvements, are still far from a market-proof solution.4-5 In this talk we present stable perovskite devices by engineering an ultra-stable 2D/3D HOOC(CH2)2NH3)2PbI4/CH3NH3PbI3 perovskite junction. The 2D/3D composite delivers an exceptional gradually organized multidimensional structure that yields up to 12.9% photovoltaic efficiency in a low cost, hole-conductor free architecture and 17% in standard mesoporous solar cells. To demonstrate the up-scale potential of this technology we fabricate 10x10 cm2 solar modules by a fully printable, industrial-scale process delivering 11.2% efficient devices which are stable for >8,500 hours with zero efficiency loss measured under standard controlled conditions. This innovative architecture will likely enable the timely commercialization of perovskite solar cells.
 National Renewable Energy Laboratory, N.R.E.L. http://www.nrel.gov/ncpv/images/efficiency_chart.jpg.
 M. Saliba, T. Matsui, J. Seo, K. Domanski, J.-P. Correa-Baena, Md.K. Nazeeruddin, S.M. Zakeeruddin, W. Tress, A. Abate, A. Hagfeldt, M. Grätzel Energy Environ. Sci. 9, 1989-1997 (2016).
 X. Li et al., Improved performance and stability of perovskite solar cells by crystal crosslinking with alkyl phosphonic acid ω-ammonium chlorides. Nat. Chem. 7, 703–711 (2015).
 I. C. Smith, E. T. Hoke, D. Solis-Ibarra, M. D. McGehee, H. I. Karunadasa, A Layered Hybrid Perovskite Solar-Cell Absorber with Enhanced Moisture Stability. Angew. Chem. 126, 11414–11417 (2014).
 K. Domanski et al., Not All That Glitters Is Gold: Metal-Migration-Induced Degradation in Perovskite Solar Cells. ACS Nano. 10, 6306–6314 (2016).