Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session M61: Energy Research -- Perovskite halidesLive
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Sponsoring Units: GERA Chair: Maria Chan, Argonne National Laboratory |
Wednesday, March 17, 2021 11:30AM - 11:42AM Live |
M61.00001: Electronic Coupling between the Organic and Inorganic Sub-Lattices of a Hybrid
Organic-Inorganic Perovskite Single Crystal Gabriel J Man, Cody Sterling, Chinnathambi Kamal, Konstantin Simonov, Sebastian Svanström, Joydev Acharya, Fredrik Johansson, Erika Giangrisostomi, Ruslan Ovsyannikov, Thomas Huthwelker, Sergei Butorin, Pabitra Nayak, Michael Odelius, Håkan Rensmo Hybrid perovskite materials have been intensively re-investigated due to their opto-electronic applications. Photoelectron spectroscopy measurements have been performed on polycrystalline films, yet the function of the organic cation remains unclear. We circumvent experimental limitations through measurements on well-defined single crystal surfaces and find evidence for electronic coupling between |
Wednesday, March 17, 2021 11:42AM - 11:54AM Live |
M61.00002: Charge Carrier Dynamics in Two-Dimensional Hybrid Perovskites: Impact of Spacer Cations Dibyajyoti Ghosh, Amanda J Neukirch, Sergei Tretiak Two-dimensional (2D) halide perovskites are promising materials for environmentally stable next-generation optoelectronic devices. However, there is very little atomistic understanding of the charge carrier dynamics at ambient conditions for these materials. Here, by combining nonadiabatic molecular dynamics with time-domain density functional theory methods at room temperature, we study the dominant non-radiative carrier recombination and dephasing processes in monolayered lead halide perovskites. Our systematic study demonstrates that performance-limiting nonradiative carrier recombination processes greatly depend on the electron-phonon interactions induced by structural fluctuations and instantaneous charge localization in these materials. The stiffer interlayer packing in presence of selectively chosen spacer cations (benzene ring/cyclic dication based), which separates the lead iodide slabs, reduces the thermal fluctuations in these 2D-perovskites to a greater extent.[1-2] These reduce the inelastic electron-phonon scattering and enhance the photogenerated charge carrier lifetime in layered perovskites making them suitable for various optoelectronic devices. |
Wednesday, March 17, 2021 11:54AM - 12:06PM Live |
M61.00003: Charge Carrier Dynamics in Bulk and 2D Perovskites Semiconductors Shashi Sourabh The effect of carrier-carrier and carrier-phonon interactions is presented in (n=1)(2D) (BA)2PbI4 Ruddlesden-Popper thin films compared to that of conventional bulk MAPbI3(n=infinity). The binding energy of excitons mediates the interaction with phonons. The strongly coupled excitons manifest themselves as small polarons that interact with lattice via the emission of LO-phonon replicas, while weakly bound excitons manifest themselves as large polarons and result in large LO-phonon broadening due to stronger carrier-phonon scattering. These results suggest that the hot carrier thermalization in perovskites is dominated by the strength and nature of the exciton-phonon interaction. To support this hypothesis, comparisons of hot carrier dynamics and electron-phonon interactions in transient absorption and CW PL are made on a number of stable and well-studied perovskite thin films (FAPbI3, FAPbBr3, and FAMASnPbI). |
Wednesday, March 17, 2021 12:06PM - 12:18PM Live |
M61.00004: Electronic stopping power in perovskites for space applications Rosty Bruce Martinez Duque, Mario Borunda Electronic stopping power describes the energy transfer rate to electrons in material during ion irradiation. We calculate electronic stopping power in triple-cation perovskites (formamidinium, methylammonium, and cesium). These materials have some of the highest power conversion efficiencies for perovskite-based photovoltaics. From simulations we can estimate the stopping process of ions and this would have implications for the use of photovoltaic devices for space missions. |
Wednesday, March 17, 2021 12:18PM - 12:30PM Live |
M61.00005: Mapping Rb-Perovskite Photovoltaics: Photovoltage and Photocurrent at the Nanoscale Richa Lahoti, John M. Howard, Md Arafat Mahmud, Thomas White, Marina S. Leite The addition of Rb+ cation at the A-site of the traditional perovskite solar cells has significantly helped in overcoming shortcomings in device performance. While some of these developments are well understood at the macroscopic level, a comprehensive study on the electrical characteristics (current and voltage) at the nanoscale remains incomplete. Here, we resolve the electrical performance of both dual-cation (Cs0.17FA0.83Pb(I0.87Br0.17)3) and quad-cation (Cs0.07Rb0.03FA0.76MA0.14Pb(I0.85Br0.15)3) perovskite solar cells by measuring photovoltage and photocurrent, spatially, at the nanoscale. Our results indicate reduced J-V hysteresis (90%), a decrease in voltage heterogeneity (34%), and a faster residual voltage decay post illumination (55%) in quad-cation perovskites imparted by Rb+ cations. We establish that quad-cation perovskite film shows half the photoinactivity seen in dual-cation perovskite. At the macroscopic level, we find that both compositions display similar photocurrent performance. Surprisingly, at the nanoscale, we unravel higher photocurrent (46%) for quadruple-cation perovskite. Further, we concluded no correlation of film morphology and grain size with photocurrent for either chemical composition. |
Wednesday, March 17, 2021 12:30PM - 12:42PM Live |
M61.00006: Facet Modulation In Perovskite Nanocrystals Debayan Mondal, Priya Mahadevan II-VI semiconductor nanocrystals have been extensively studied by soft chemistry method. In addition to a control on the size, one has found modulation of the shape under various experimental conditions. This increases the surface area for similar sized objects and facilitates use in various applications such as catalysis where the increased surface area would imply more active sites. While experiments on hybrid perovskites have found only cubic facets , recently it was shown for CsPbX3 (X= Br,Cl) under certain experimental conditions [1] one found a faceted polyhedron which could be transformed into a hexapod. We will present our recent theoretical studies which examine the stability of different facets and show how a modulation is possible. |
Wednesday, March 17, 2021 12:42PM - 12:54PM Live |
M61.00007: Understanding the role of Sn substitution and Pb-Vc in enhancing the optical properties and solar cell efficiency of CH(NH2)2Pb1−X−YSnXVcYBr3 Manjari Jain, Saswata Bhattacharya Formamidinium Lead Bromide (FAPbBr3) perovskite has drawn scientific interest in the field of optoelectronic devices. However, the presence of highly toxic lead restricts its application. We address here the role of Sn substitution and Pb vacancy (Pb-Vc) in regulating stability using state-of-the-art hybrid density functional theory. The explicit role of spin orbit coupling (SOC) and electron self interaction error are discussed. We find while SOC has a significant role in regulating electronic bands, it doesn't affect the relative hierarchy of thermodynamic stability of different configurations of FAPb(1-x-y)SnxVcyBr3. Further, the co-existence of Sn substitution and Pb-Vc have been found to be thermodynamically stable via ab initio thermodynamics approach. However, Pb-Vc introduces trap states deep inside the forbidden gap, which leads to electron-hole recombination centers. Therefore, the stable configurations with only Sn substitution (FAPb1−X SnX Br3) are considered for further optical study. Because of the better optical properties, higher absorption coefficient, and larger spectroscopic limited maximum efficiency (SLME) values, the mixed perovskite FAPb1−X SnX Br3 with 0 ≤ X ≤ 0.5 are considered to be promising candidates for solar cell application. |
Wednesday, March 17, 2021 12:54PM - 1:06PM Live |
M61.00008: Influence of Lead Thiocyanate on the Optical Properties and Stability of All-Inorganic Lead Halide Perovskite Nanocrystals for Lighting Applications Saroj Thapa, Gopi C Adhikari, Hongyang Zhu, Peifen Zhu All-inorganic lead halide perovskite (CsPbX3, X = Cl−, Br−, I−) nanocrystals (NCs) are promising materials for illumination and display applications because of low-cost, high photoluminescence quantum yields (PLQYs), as well as narrow and tunable emission spectra. However, the low stability issue of these NCs in the presence of air and moisture impedes their practical utilization. In this study, we reported that the addition of lead thiocyanate [Pb(SCN)2] during the synthesis of CsPbX3 NCs helps to improve the stability and optical properties of the resulting NCs. With an increasing concentration of Pb(SCN)2, the thiocyanate (SCN−)-based NCs demonstrate narrower and tunable emission spectra with a substantial increase in PLQYs. Besides, the SCN−-based NCs retain higher photoluminescence intensity (three times higher) compared to the host NCs, when stored in an ambient environment for several days. This suggests the betterment in the stability of as-grown NCs against air and moisture. Finally, the implications of these different colors (green, yellow, and red) emitting NCs as the color conversion layer results in bright neutral white light with a correlated color temperature of 5148 K and a high color rendering index of 91. |
Wednesday, March 17, 2021 1:06PM - 1:18PM Live |
M61.00009: Understanding nucleation and growth kinetics of hybrid perovskite microstructures using ultrafast spectroscopy. Bibek Singh Dhami, Ravi P.N. Tripathi, David J. Hoxie, Uddhab Tiwari, Kannatassen Appavoo Understanding at which stage during the growth process does hybrid perovskite first displays its characteristic optical signature is critical for optimizing large-scale fabrication such as roll-to-roll printing and slot-die coating. Here, by spatially controlling the growth conditions of solution-processed hybrid perovskite using a thermal gradient technique, we fabricate hybrid perovskite that progressively changes from microstructures to large-grain thin films on the same substrate. Consequently, samples fabricated this way allows us to correlate how the structure and nanoscale morphology affect the overall optical response, where a combination of x-ray diffraction, scanning electron microscopy and spectral emission mapping microscopy are employed. Importantly, we conduct ultrafast broadband pump-probe microscopy to assess the carrier dynamics of our sample. Interestingly, we find that the initial nucleating microcrystals already exhibit the characteristics optical properties of large-grain thin films. |
Wednesday, March 17, 2021 1:18PM - 1:30PM Live |
M61.00010: Comparison of deposition techniques for hybrid perovskite solar cells Kevser Sahin Tiras, Markus Wohlgenannt, Fatima Toor We examined three different fabrication techniques; single-step solution, two-step solution and solution-assisted vapor deposition to fabricate perovskite films and solar cells. The morphology of the surface and the grain size of the perovskite crystal were mainly affected by lead iodide (PbI2) layer thickness and methylammonium iodide (MAI) concentration rate. For each fabrication technique, absorption spectrum and scanning electron microscope (SEM) images of the perovskite films were evaluated. We measured the power conversion efficiency (PCE) of the solar cells within these techniques. The device made with two-step solution deposition technique showed the highest PCE among solar cells prepared using other perovskite deposition techniques. To improve the cell performance, we also used some of the well-known device engineering methods, such as process and contact engineering. |
Wednesday, March 17, 2021 1:30PM - 1:42PM Live |
M61.00011: Effects of Anti-solvent Wash on Solvent Engineered Methylammonium Lead Bromide Perovskites for Light-emitting Diode Applications Emily Enlow, Kaitlin L Hellier, Carey Williams, Roy M Sfadia, Sue Carter Organometal halide perovskites have shown promise for optoelectronic devices such as solar cells and light-emitting diodes (LEDs). Perovskite optoelectronic devices offer an advantage over traditional semiconductor devices due to their potential to be made at low cost using solution processing while maintaining excellent electronic properties. Currently, the efficiencies of LEDs made using perovskites are still lacking compared to organic LEDs and inorganic LEDs. The role of fabrication on crystal formation for bromide perovskite systems is still not fully understood. To further this understanding, this work compares the effects of different anti-solvents when creating solvent engineered MAPbBr3 films with a focus on LED applications. The crystal structure of the films was confirmed via XRD. The film surface morphology was characterized using AFM; SEM was used to identify grain size and internal morphology. Photoluminescence was used to compare the different anti-solvents. Photothermal deflection spectroscopy was used to compare trap densities and general order within the films. Finally, LEDs were made using films of each anti-solvent wash, demonstrating the effect of the antisolvent on device performance. |
Wednesday, March 17, 2021 1:42PM - 1:54PM Not Participating |
M61.00012: Capturing excitonic effects in lead iodide perovskites from many-body perturbation theory Pooja Basera, Saswata Bhattacharya Lead iodide perovskites have attracted considerable interest as promising energy-materials. However, till date, several key electronic properties such as optical properties, effective mass, exciton binding energy, and the radiative exciton lifetime are largely unknown. Here, we employ an integrated approach with several state-of-the-art first-principles based methodologies viz. hybrid Density Functional Theory combined with spin-orbit coupling, many-body perturbation theory, model-BSE (mBSE), Wannier-Mott and Density Functional Perturbation Theory to address these properties by taking a prototypical model system viz. APbI3 (A = Formamidinium (FA), methylammonium (MA), and Cs). We demonstrate that while the mBSE approach improves the excitonic feature in the optical spectra, the Wannier-Mott approach and ionic contribution to dielectric screening ameliorate the exciton binding energy. Moreover, the direct-indirect band gap transition (Rashba-Dresselhaus splitting) may be responsible for the reduced charge carrier recombination rate in MAPbI3 and FAPbI3. The role of cation “A” for procuring the long-lived exciton lifetime is well understood. |
Wednesday, March 17, 2021 1:54PM - 2:30PM Live |
M61.00013: Phonon screening of electron-hole interactions in lead-halide perovskite semiconductors and beyond Invited Speaker: Marina Filip Electronic and optical excitations are strongly influenced by the dielectric of properties |
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