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1. Controlling processing temperatures and self-limiting behaviour in intense pulsed sintering by tailoring nanomaterial shape distribution

   https://doi.org/10.1039/C7RA11013H  

   Dexter, M. ; Bhandari, R. ; Chang, C-H. ; Malhotra, R. ( January 2017 , RSC Advances)

   Intense Pulsed Light Sintering (IPL) uses pulsed, large-area, broad-spectrum visible light from a xenon lamp for rapid fusion of nanomaterials into films or patterns used in flexible sensors, solar cells, displays and other applications. Past work on the IPL of silver nanoparticles has shown that a self-damping coupling between densification and optical absorption governs the evolution of the deposited nanomaterial temperature during IPL. This work examines the influence of the nanomaterial shape distribution on this coupling and on the temperature evolution in IPL of silver nanowire–nanoparticle composite films. The film thickness, resistivity, micromorphology, crystallinity and optical properties are compared formore »varying ratios of nanowire to nanoparticle content in the film. It is shown for the first time, that increasing the nanowire content reduces the maximum film temperature during IPL from 240 °C to 150 °C and substantially alters the temperature evolution trends over consecutive pulses, while enabling film resistivity within 4–5 times that of bulk silver in 2.5 seconds of processing time. Nanoscale electromagnetic models are used to understand optical absorption as a function of changing ratio of nanowires to nanoparticles in a model assembly that emulates the IPL experiments performed here. The coupling between densification and optical absorption is found to inherently depend on the nanomaterial shape distribution and the ability of this phenomenon to explain the experimental temperature evolution trends is discussed. The implications of these observations for controlling self-damping coupling in IPL and the optimum nanoparticle to nanowire ratios for concurrently achieving high throughput, low processing temperatures, low material costs and low resistivity in IPL of conductive metallic nanomaterials are also described.« less
2. A Hybrid Desktop Process for Integrated Deposition and Low-cost, In-situ Sintering of Conductive Silver Nanoparticles

   Bhandari, Roshan ; Bansal, Shalu ; Dexter, Michael ; Malhotra, Rajiv ( March 2017 , World Congress on Micro and Nano Manufacturing)

   Microscale continuous thin films or patterned conductive structures find applications in thin film electronics, energy generation and functional sensor systems. An emerging alternative to conventional vacuum based deposition of such structures is the additive deposition and sintering of conductive nanoparticles, to enable low temperature, low-cost and low energy fabrication. While significant work has gone into additive deposition of nanoparticles the realization of the above potential needs nanoparticle sintering methods that are equally low-cost, in-situ, ambient condition and desktop-sized in nature. This work demonstrates the integration of non-laser based, low-cost and small footprint optical energy sources for ambient condition sintering ofmore »conductive nanoparticles, with wide-area aerosol jet based additive printing of nanoparticle inks. The nanoparticle sintering is characterized by quantifying the sintering temperatures, sintered material conductivity, crystallinity, optical properties, thickness and microscale morphology in terms of the sintering parameters. It is shown that such optical sintering sources can be further integrated with inkjet printing as well, and the implications on new paradigms for hybrid additive-« less
3. The Coupling Between Densification and Optical Heating in Intense Pulsed Light Sintering of Silver Nanoparticles

   https://doi.org/10.1115/MSEC2016-8693  

   Bansal, Shalu ; Chang, Chih-Hung ; Malhotra, Rajiv ( June 2016 , ASME 2016 11th International Manufacturing Science and Engineering Conference)

   Sintering of nanoparticles deposited onto rigid or flexible substrate is required for many devices that use continuous and patterned thin films. An emerging need in this area is to perform nanoparticle sintering under ambient conditions, at high speeds, and with throughput that is compatible with high speed nanoparticle deposition techniques. Intense Pulsed Light sintering (IPL) uses a high energy, broad area and broad spectrum beam of xenon lamp light to sinter metallic and non-metallic nanoparticles. The capability of IPL to meet the above needs has been demonstrated. This paper experimentally examines temperature evolution and densification during IPL. It is shown,more »for the first time, that temperature rise and densification in IPL are related to each other. A coupled optical-thermal-sintering model on the nanoscale is developed, to understand this phenomenon. This model is used to show that the change in nanoscale shape of the nanoparticle ensemble due to sintering, reduces the optically induced heating as the densification proceeds, which provides a better explanation of experimental observations as compared to current models of IPL. The implications of this new understanding on the performance of IPL are also discussed.« less
4. Rapid thermal annealing of CH ₃ NH ₃ PbI ₃ perovskite thin films by intense pulsed light with aid of diiodomethane additive

   https://doi.org/10.1039/c8ta01237g  

   Ankireddy, Krishnamraju ; Ghahremani, Amir H. ; Martin, Blake ; Gupta, Gautam ; Druffel, Thad ( January 2018 , Journal of Materials Chemistry A)

   The organic metal halide perovskite material is capable of high throughput manufacturing via traditional deposition processes used in roll-to-roll, yet thermal annealing post deposition may require long ovens. We report rapid annealed perovskite thin films using intense pulsed light (IPL) to initiate a radiative thermal response that is enabled by an alkyl halide additive that collectively improves the performance of a device processed in an ambient environment from a baseline of 10 to 16.5% efficiency. Previous reports on CH 3 NH 3 PbI 3 perovskite films using IPL processing achieved functional devices in milli-second time scales and are promising formore »high throughput manufacturing processes under ambient conditions. In this study, we found that the addition of diiodomethane (CH 2 I 2 ) as an additive to the methylammonium iodide (MAI)/lead iodide (PbI 2 ) precursor ink chemistry and subsequent IPL thermal annealing are inter-dependent. The concentration of CH 2 I 2 and IPL processing parameters have a direct effect on the surface morphology of the films and performance within a perovskite solar cell (PSC). The CH 2 I 2 dissociates under exposure to ultraviolet (UV) radiation from the IPL source liberating iodine ions in the film, influencing the perovskite formation and reducing the defect states. We anticipate that these results can be utilized to further develop different ink formulations using alkyl halides for the IPL technique to improve the performance of perovskite solar cells processed in ambient conditions.« less
5. Large-Scale Synthesis of Semiconducting Cu(In,Ga)Se2 Nanoparticles for Screen Printing Application

   https://doi.org/10.3390/nano11051148  

   Gonçalves, Bruna F. ; LaGrow, Alec P. ; Pyrlin, Sergey ; Owens-Baird, Bryan ; Botelho, Gabriela ; Marques, Luis S. ; Ramos, Marta M. ; Kovnir, Kirill ; Lanceros-Mendez, Senentxu ; Kolen’ko, Yury V. ( May 2021 , Nanomaterials)

   During the last few decades, the interest over chalcopyrite and related photovoltaics has been growing due the outstanding structural and electrical properties of the thin-film Cu(In,Ga)Se2 photoabsorber. More recently, thin film deposition through solution processing has gained increasing attention from the industry, due to the potential low-cost and high-throughput production. To this end, the elimination of the selenization procedure in the synthesis of Cu(In,Ga)Se2 nanoparticles with following dispersion into ink formulations for printing/coating deposition processes are of high relevance. However, most of the reported syntheses procedures give access to tetragonal chalcopyrite Cu(In,Ga)Se2 nanoparticles, whereas methods to obtain other structures aremore »scarce. Herein, we report a large-scale synthesis of high-quality Cu(In,Ga)Se2 nanoparticles with wurtzite hexagonal structure, with sizes of 10–70 nm, wide absorption in visible to near-infrared regions, and [Cu]/[In + Ga] ≈ 0.8 and [Ga]/[Ga + In] ≈ 0.3 metal ratios. The inclusion of the synthesized NPs into a water-based ink formulation for screen printing deposition results in thin films with homogenous thickness of ≈4.5 µm, paving the way towards environmentally friendly roll-to-roll production of photovoltaic systems.« less