Session Chair: Eric Wei-Guang Diau, National Chiao Tung University Session Chair: Osman Bakr, King Abdullah University of Science and Technology
4:00pm - 4:30pm Invited
Synthetic Manipulation of Hybrid Perovskite Systems in Search of Novel and Enhanced Functionality
Indian Institute of Science Education and Research, Pune, India
Hybrid perovskites are at the centre of scientific attention in recent years in view of the remarkably high solar conversion efficiency values realized in solar cells based on these materials. The ensuing research has brought out several peculiarities of these novel tunable materials that continue to elude full understanding of the attendant phenomena. Moreover applications of such opto-electronically interesting systems are beginning to be explored in other fields. This has encouraged research in manipulating hybrid perovskites for seeking either enhanced or novel functionalities. I will discuss examples of this research deriving from own work on molecular ion substitution, small molecule incorporation effects on film growth and properties, synthesis and properties of 2D hybrid perovskites, synthesis of quantum structures using electro-spray solvent extraction method, QD incorporation effects etc. I will also discuss a few novel applications of these materials.
Funding Support: RCUK-DST (APEX-II), DST (CERI), MNRE, Govt. of India.
4:30pm - 5:00pm Invited
Single-walled Carbon Nanotubes Enhance the Efficiency and Stability of Nanocrystalline TiO2 Photoelectrode Based Perovskite Solar Cells
Joseph George SHAPTER1, Cameron SHEARER1, Munkhjargal BAT-ERDENE1, Munkhbayar BATMUNKH1, Mark BIGGS2
1Flinders University, Australia; 2School of Science, Loughborough University, United Kingdom
Nanocarbons are unique materials that have been extensively used in a wide range of applications including various photovoltaic devices. The present work reports a significant enhancement in the efficiency and stability of perovskite solar cells (PSCs) by incorporating single-walled carbon nanotubes (SWCNTs) into the nanocrystalline TiO2 photoelectrode. It was found that SWCNTs provide both rapid electron transfer and advantageously shifts the conduction band minimum of the TiO2 photoelectrode and thus enhances all photovoltaic parameters of PSCs. The TiO2-SWCNTs photoelectrode based PSC device exhibited a power conversion efficiency (PCE) of up to 16.11%, while the cell fabricated without SWCNTs displayed an efficiency of 13.53%. More importantly, we found that the SWCNTs in the TiO2 NPs based photoelectrode suppress the hysteresis behavior and significantly enhance both the light and long-term storage-stability of the PSC devices. The present work provides important guidance for future investigations in utilizing carbonaceous materials for solar cells.
5:00pm - 5:15pm Oral
Novel Approach to Synthesize Defect Free Lead Halide Perovskite Crystals
Pronoy NANDI, Chandan GIRI, Dinesh TOPWAL
Institute of Physics, Bhubaneswar, India
Methylammonium lead halides (CH3NH3PbX3; X= I, Br, Cl) are one of the most commonly used perovskite material proposed for making photovoltaic devices, photodetectors, lasers and light-emitting diodes (LEDs). Macroscopic single crystals are crucial for both fundamental studies and efficient devices. It was reported that single crystals with low trap state densities will show better optoelectronic properties. Large hybrid perovskite crystals can be prepared through a variety of solution based approaches, such as the conventional cooling technique, top seeded growth, anti-solvent vapor assisted crystallization method and inverse temperature crystallization method. In our study, basically we focused to grow defect free single crystals and we have grown single crystals of CH3NH3PbBr3 by four different techniques:- inverse temperature crystallization method, conventional cooling method, Ethyl-acetate (high boiling point antisolvent) and dichloromethane (low boiling point antisolvent) diffusion crystallization method. From UV-VIS absorption study, temperature dependent photoluminescence study and magnetization study we confirmed Ethyl-acetate antisolvent diffusion will produce less defective single crystal sample out of above all four samples. From temperature dependent photoluminescence and absorption study we observed a broad peak from 600-700 nm and time resolved photoluminescence confirmed this peak has higher decay time (~micro sec) than that of band edge transition (~nanosec.). Comparing with the formation energy calculation with the experimentally obtained energy level we assumed that excess amount of Pb in interstitial positions create defect levels which was confirmed by dc magnetization study.
5:15pm - 5:30pm Oral
Anisotropic Moisture Erosion of CH3NH3PbI3 Single Crystal
Qianrui LV, Wenhui HE, Zhipeng LIAN, Jie DING, Qiang LI, Qingfeng YAN
Department of Chemistry, Tsinghua University, China.
Methylammonium lead halide perovskites have been intensively studied as light harvesting materials in a variety of optoelectronic devices. However, their chemical sensitivity is one of the critical obstacles for device application.  In particular, water can cause their degradation: CH3NH3PbI3 → CH3NH3I + PbI2.  Optoelectronic devices based on CH3NH3PbI3 single crystals show better performance than that based on CH3NH3PbI3 polycrystalline film.  However, few studies have focused on the water erosion of CH3NH3PbI3 single crystals. In this work, the anisotropy of moisture erosion was firstly observed in CH3NH3PbI3 single crystals. When exposed to moisture, the (001) facet exhibited greater sensitivity to water molecules and showed a faster erosion rate compared to the (100) facet and (112) facet, which resulted from the differences in respective atomic arrangements along each crystal orientation and the varied penetration paths for H2O molecules. Revealing the anisotropy of moisture erosion for the CH3NH3PbI3 single crystal extends understanding of the erosion process and guides the design of more stable single-crystal-based perovskite devices in future.
 D. Wang, M. Wright, N. K. Elumalai and A. Uddin, Sol. Energy Mater. Sol. Cells,2016, 147, 255-275.
 G. Niu, W. Li, F. Meng, L. Wang, H. Dong and Y. Qiu, J. Mater. Chem. A,2014, 2, 705-710.
 Z. Lian, Q. Yan, Q. Lv, Y. Wang, L. Liu, L. Zhang, S. Pan, Q. Li, L. Wang and J.-L. Sun, Sci. Rep., 2015, 5, 16563.
5:30pm - 5:45pm Oral
Novel Inorganic-organic 2D Perovskite Based Nanocomposite Fabrication Strategy for Photonic Device Applications
Pawan Kumar KANAUJIA, G. Vijaya PRAKASH
Indian Institute of Technology Delhi, India
Inorganic-organic (IO) perovskite materials have emerged as a potential candidate for optoelectronic applications in a very short time span. Among these IO perovskites, 2D layered networks ((R-NH3)2MX4 type) are of special interest. These are considered to be self-assembled multiple quantum wells, made up of alternating stack of inorganic semiconducting monolayers and large band gap organic spacer moieties. These materials exhibit strong room temperature optical excitons confined within the semiconductor layers, leading to many new optoelectronic applications. However, some bottlenecks are large-scale mass production, understanding of structural deformation and so on. We demonstrate a novel, simple but effective methodology to fabricate inorganic-organic hybrid nanocomposites embedded in nanoporous materials and long-chain polymer matrices to improve the stability and performance. The aim is to integrate the advantages from both systems into a single entity without losing their individual qualities. These innovative nanocomposites may open a pathway towards new optical and optoelectronic device applications with improved performance.