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148 results on '"Lahtonen, Kimmo"'

2. Halide Engineering in Mixed Halide Perovskite-Inspired Cu2AgBiI6 for Solar Cells with Enhanced Performance

Author

Sugathan, Vipinraj, primary, Liu, Maning, additional, Pecoraro, Adriana, additional, Das, T. Kumar, additional, Ruoko, Tero-Petri, additional, Grandhi, G. Krishnamurthy, additional, Manna, Debjit, additional, Ali-Löytty, Harri, additional, Lahtonen, Kimmo, additional, Muñoz-García, Ana Belén, additional, Pavone, Michele, additional, and Vivo, Paola, additional

Published
2024
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11. Less Is More: Simplified Fluorene-Based Dopant-Free Hole Transport Materials Promote the Long-Term Ambient Stability of Perovskite Solar Cells

Author

Mäkinen, Paavo, primary, Fasulo, Francesca, additional, Liu, Maning, additional, Grandhi, G. Krishnamurthy, additional, Conelli, Daniele, additional, Al-Anesi, Basheer, additional, Ali-Löytty, Harri, additional, Lahtonen, Kimmo, additional, Toikkonen, Sami, additional, Suranna, Gian Paolo, additional, Muñoz-García, Ana Belén, additional, Pavone, Michele, additional, Grisorio, Roberto, additional, and Vivo, Paola, additional

Published
2023
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14. Antimony-bismuth alloying: the key to a major boost in the efficiency of lead-free perovskite-inspired indoor photovoltaics

Author

Al-Anesi, Basheer, primary, Grandhi, G. Krishnamurthy, additional, Pecoraro, Adriana, additional, Sugathan, Vipinraj, additional, Viswanath, N.S.M., additional, Ali-Löytty, Harri, additional, Liu, Maning, additional, Ruoko, Tero-Petri, additional, Lahtonen, Kimmo, additional, Manna, Debjit, additional, Toikkonen, Sami, additional, Muñoz-García, Ana Belén, additional, Pavone, Michele, additional, and Vivo, Paola, additional

Published
2023
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16. Triple A‐Site Cation Mixing in 2D Perovskite‐Inspired Antimony Halide Absorbers for Efficient Indoor Photovoltaics

Author

Lamminen, Noora, primary, Grandhi, Gopal Krishnamurthy, additional, Fasulo, Francesca, additional, Hiltunen, Arto, additional, Pasanen, Hannu, additional, Liu, Maning, additional, Al‐Anesi, Basheer, additional, Efimov, Alexander, additional, Ali‐Löytty, Harri, additional, Lahtonen, Kimmo, additional, Mäkinen, Paavo, additional, Matuhina, Anastasia, additional, Muñoz‐García, Ana Belén, additional, Pavone, Michele, additional, and Vivo, Paola, additional

Published
2022
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19. Enhancing the Microstructure of Perovskite‐Inspired Cu‐Ag‐Bi‐I Absorber for Efficient Indoor Photovoltaics (Small 35/2022)

Author

Grandhi, G. Krishnamurthy, primary, Al‐Anesi, Basheer, additional, Pasanen, Hannu, additional, Ali‐Löytty, Harri, additional, Lahtonen, Kimmo, additional, Granroth, Sari, additional, Christian, Nino, additional, Matuhina, Anastasia, additional, Liu, Maning, additional, Berdin, Alex, additional, Pecunia, Vincenzo, additional, and Vivo, Paola, additional

Published
2022
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25. Triple A‐Site Cation Mixing in 2D Perovskite‐Inspired Antimony Halide Absorbers for Efficient Indoor Photovoltaics.

Author

Lamminen, Noora, Grandhi, Gopal Krishnamurthy, Fasulo, Francesca, Hiltunen, Arto, Pasanen, Hannu, Liu, Maning, Al‐Anesi, Basheer, Efimov, Alexander, Ali‐Löytty, Harri, Lahtonen, Kimmo, Mäkinen, Paavo, Matuhina, Anastasia, Muñoz‐García, Ana Belén, Pavone, Michele, and Vivo, Paola

Subjects
PHOTOVOLTAIC power generation, ANTIMONY, QUANTUM efficiency, HALIDES, CATIONS, CESIUM
Abstract

Antimony‐based perovskite‐inspired materials (PIMs) are solution‐processable halide absorbers with interesting optoelectronic properties, low toxicity, and good intrinsic stability. Their bandgaps around 2 eV make them particularly suited for indoor photovoltaics (IPVs). Yet, so far only the fully inorganic Cs3Sb2ClxI9−x composition has been employed as a light‐harvesting layer in IPVs. Herein, the first triple‐cation Sb‐based PIM (CsMAFA‐Sb) in which the A‐site of the A3Sb2X9 structure consists of inorganic cesium alloyed with organic methylammonium (MA) and formamidinium (FA) cations is introduced. Simultaneously, the X‐site is tuned to guarantee a 2D structure while keeping the bandgap nearly unchanged. The presence of three A‐site cations is essential to reduce the trap‐assisted recombination pathways and achieve high performance in both outdoor and indoor photovoltaics. The external quantum efficiency peak of 77% and the indoor power conversion efficiency of 6.4% are the highest values ever reported for pnictohalide‐based photovoltaics. Upon doping of the P3HT hole‐transport layer with F4‐TCNQ, the power conversion efficiency of CsMAFA‐Sb devices is fully retained compared to the initial value after nearly 150 days of storage in dry air. This work provides an effective compositional strategy to inspire new perspectives in the PIM design for IPVs with competitive performance and air stability. [ABSTRACT FROM AUTHOR]

Published
2023
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29. Reactive laser interference patterning on titanium and zinc in high pressure CO2.

Author

Singh, Amandeep, Kumpulainen, Tero, Lahtonen, Kimmo, Söyrinki, Saara, Vihinen, Jorma, and Levänen, Erkki

Subjects
X-ray emission spectroscopy, FIELD emission electron microscopy, TITANIUM, ATOMIC force microscopy, ZINC, X-ray photoelectron spectroscopy
Abstract

Direct laser interference patterning (DLIP) is a versatile technique for surface patterning that enables formation of micro-nano sized periodic structures on top of the target material. In this study, DLIP in high pressure, supercritical and liquid CO2 by 4-beam DLIP was used to pattern titanium and zinc targets. Field emission scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy was used to characterize the patterned surfaces. Field emission SEM analysis showed presence of ordered uniform donut ring pattern with hollow centers for both titanium and zinc with a period slightly under 3 µm while topographical images from atomic force microscopy revealed donut rings protruding outwards typically around 200 nm from target surface and consisted of a crevice at the center with a depth typically around 300 nm and 250 nm for titanium and zinc target, respectively. Based on X-ray photoelectron spectroscopic analysis, this is the first study to report formation of TiO2, TiC, ZnCO3, and zinc hydroxy carbonate on the pattern by DLIP in supercritical and liquid CO2 for titanium and zinc targets. Pressurized CO2 is demonstrated as a promising environment with mirror-based DLIP system for reactive patterning. Due to the superior transport properties and solvent power of supercritical CO2, the current study opens possibilities for reactive patterning in environments that may not have been previously possible. [ABSTRACT FROM AUTHOR]

Published
2022
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30. Reactive laser interference patterning on titanium and zinc in high pressure CO2.

Author

Singh, Amandeep, Kumpulainen, Tero, Lahtonen, Kimmo, Söyrinki, Saara, Vihinen, Jorma, and Levänen, Erkki

Subjects
X-ray emission spectroscopy, FIELD emission electron microscopy, TITANIUM, ATOMIC force microscopy, ZINC, X-ray photoelectron spectroscopy
Abstract

Direct laser interference patterning (DLIP) is a versatile technique for surface patterning that enables formation of micro-nano sized periodic structures on top of the target material. In this study, DLIP in high pressure, supercritical and liquid CO2 by 4-beam DLIP was used to pattern titanium and zinc targets. Field emission scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy was used to characterize the patterned surfaces. Field emission SEM analysis showed presence of ordered uniform donut ring pattern with hollow centers for both titanium and zinc with a period slightly under 3 µm while topographical images from atomic force microscopy revealed donut rings protruding outwards typically around 200 nm from target surface and consisted of a crevice at the center with a depth typically around 300 nm and 250 nm for titanium and zinc target, respectively. Based on X-ray photoelectron spectroscopic analysis, this is the first study to report formation of TiO2, TiC, ZnCO3, and zinc hydroxy carbonate on the pattern by DLIP in supercritical and liquid CO2 for titanium and zinc targets. Pressurized CO2 is demonstrated as a promising environment with mirror-based DLIP system for reactive patterning. Due to the superior transport properties and solvent power of supercritical CO2, the current study opens possibilities for reactive patterning in environments that may not have been previously possible. [ABSTRACT FROM AUTHOR]

Published
2022
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34. Selective atomic layer deposition on flexible polymeric substrates employing a polyimide adhesive as a physical mask

Author

Forouzmehr, Matin, Zambou, Serges, Lahtonen, Kimmo, Honkanen, Mari, Nazmul Anam, Rafi Md, Ruhanen, Aleksi, Rokaya, Chakra, Lupo, Donald, Berger, Paul R., Tampere University, Electrical Engineering, Physics, and Materials Science and Environmental Engineering

Subjects
213 Electronic, automation and communications engineering, electronics, 216 Materials engineering
Abstract

The rise of low-temperature atomic layer deposition (ALD) has made it very attractive to produce high- κ dielectric for flexible electronic devices. Similarly, selective deposition of ALD films is of great relevance for circuitry. We demonstrated a simple method of using a physical mask to block the film's growth in selected polymeric and flexible substrate areas during a low-pressure ALD process. A low-cost silicone adhesive polyimide tape was used to manually mask selected areas of bare substrates and aluminum strips deposited by evaporation. 190 cycles of aluminum oxide (Al 2O 3) and hafnium oxide (HfO 2) were deposited at temperatures ranging from 100 to 250 °C. Using x-ray photoelectron spectroscopy (XPS) analysis and energy dispersive x-ray spectroscopy (EDS), we showed that the mask was effective in protecting the areas under the tape. The mask did not show any modification of shape for an exposure of 10 h at 250 °C, hence keeping the form of the masked area intact. An analysis of the unmasked area by ellipsometry (632.8 nm) and x ray shows a regular film with a thickness variation under 2 nm for a given temperature and constant refractive index. EDS, selected-area XPS, and imaging XPS show an evident change of elemental content at the interface of two areas. By XPS, we established that the structure of the films was not affected by the mask, the films were stoichiometric, and there was no effect of outgassing from the adhesive film. publishedVersion

Published
2021

37. GaAs surface passivation for InAs/GaAs quantum dot based nanophotonic devices

Author

Chellu, Abhiroop, primary, Koivusalo, Eero, additional, Raappana, Marianna, additional, Ranta, Sanna, additional, Polojärvi, Ville, additional, Tukiainen, Antti, additional, Lahtonen, Kimmo, additional, Saari, Jesse, additional, Valden, Mika, additional, Seppänen, Heli, additional, Lipsanen, Harri, additional, Guina, Mircea, additional, and Hakkarainen, Teemu, additional

Published
2021
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44. Moisture-Assisted near-UV Emission Enhancement of Lead-Free Cs4CuIn2Cl12Double Perovskite Nanocrystals

Author

Liu, Maning, Matta, Sri Kasi, Ali-Löytty, Harri, Matuhina, Anastasia, Grandhi, G. Krishnamurthy, Lahtonen, Kimmo, Russo, Salvy P., and Vivo, Paola

Abstract

Lead-based halide perovskite nanocrystals (NCs) are recognized as emerging emissive materials with superior photoluminescence (PL) properties. However, the toxicity of lead and the swift chemical decomposition under atmospheric moisture severely hinder their commercialization process. Herein, we report the first colloidal synthesis of lead-free Cs4CuIn2Cl12layered double perovskite NCs via a facile moisture-assisted hot-injection method stemming from relatively nontoxic precursors. Although moisture is typically detrimental to NC synthesis, we demonstrate that the presence of water molecules in Cs4CuIn2Cl12synthesis enhances the PL quantum yield (mainly in the near-UV range), induces a morphological transformation from 3D nanocubes to 2D nanoplatelets, and converts the dark transitions to radiative transitions for the observed self-trapped exciton relaxation. This work paves the way for further studies on the moisture-assisted synthesis of novel lead-free halide perovskite NCs for a wide range of applications.

Published
2022
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48. Halide Engineering in Mixed Halide Perovskite-Inspired Cu2AgBiI6for Solar Cells with Enhanced Performance

Author

Sugathan, Vipinraj, Liu, Maning, Pecoraro, Adriana, Das, T. Kumar, Ruoko, Tero-Petri, Grandhi, G. Krishnamurthy, Manna, Debjit, Ali-Löytty, Harri, Lahtonen, Kimmo, Muñoz-García, Ana Belén, Pavone, Michele, and Vivo, Paola

Abstract

Cu2AgBiI6(CABI) is a promising perovskite-inspired absorber for solar cells due to its direct band gap and high absorption coefficient. However, the nonradiative recombination caused by the high extrinsic trap density limits the performance of CABI-based solar cells. In this work, we employ halide engineering by doping bromide anions (Br–) in CABI thin films, in turn significantly improving the power conversion efficiency (PCE). By introducing Br–in the synthetic route of CABI thin films, we identify the optimum composition as CABI-10Br (with 10% Br at the halide site). The tailored composition appears to reduce the deep trap density as shown by time-resolved photoluminescence and transient absorption spectroscopy characterizations. This leads to a dramatic increase in the lifetime of charge carriers, which therefore improves both the external quantum efficiency and the integrated short-circuit current. The photovoltaic performance shows a significant boost since the PCE under standard 1 sun illumination increases from 1.32 to 1.69% (∼30% relative enhancement). Systematic theoretical and experimental characterizations were employed to investigate the effect of Br–incorporation on the optoelectronic properties of CABI. Our results highlight the importance of mitigating trap states in lead-free perovskite-inspired materials and that Br–incorporation at the halide site is an effective strategy for improving the device performance.

Published
2024
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