Hiroyuki Kanda

Foldable Hole-Transporting Materials for Merging Electronic States between Defective and Perfect Perovskite Sites

Keith Gregory Brooks, Paul Joseph Dyson, Ruiyuan Hu, Hiroyuki Kanda, Mohammad Khaja Nazeeruddin, Kasparas Rakstys, Jianxing Xia, Yi Zhang

Defective and perfect sites naturally exist within electronic semiconductors, and considerable efforts to reduce defects to improve the performance of electronic devices, especially in hybrid organic-inorganic perovskites (ABX(3)), are undertaken. Herein, foldable hole-transporting materials (HTMs) are developed, and they extend the wavefunctions of A-site cations of perovskite, which, as hybridized electronic states, link the trap states (defective site) and valence band edge (perfect site) between the naturally defective and perfect sites of the perovskite surface, finally converting the discrete trap states of the perovskite as the continuous valence band to reduce trap recombination. Tailoring the foldability of the HTMs tunes the wavefunctions between defective and perfect surface sites, allowing the power conversion efficiency of a small cell to reach 23.22% and that of a mini-module (6.5 x 7 cm, active area = 30.24 cm(2)) to reach as high as 21.71% with a fill factor of 81%, the highest value reported for non-spiro-OMeTAD-based perovskite solar modules.

WILEY-V C H VERLAG GMBH2023

Transparent Liquid Crystal Hole-Transporting Material for Stable Perovskite Solar Cells

Hiroyuki Kanda, Mohammad Khaja Nazeeruddin, Kasparas Rakstys, Jianxing Xia

Hexakis(hexyloxy)triphenylene (HAT6) discotic liquid crystal is employed as a transparent hole-transporting material (HTM) for perovskite solar cells (PSCs) and a power conversion efficiency (PCE) of 15.7% is obtained, which is the highest using HAT6 type of HTMs. Despite lower PCE than spiro-OMeTAD-based devices (20.3%), the PSCs based on HAT6 exhibit much higher ambient and thermal stability. A fused polyaromatic core with six alkyl chains leads to high hydrophobicity, and the pi-stacked molecular columns of the HAT6 shield the bis(trifluoromethane)sulfonamide lithium salt dopant migration into the perovskite absorber. The PSCs (under N-2 condition) exhibit superior stability compared to the devices employing spiro-OMeTAD, retaining nearly 92% of their initial efficiency after 1200 h operation. Under ambient conditions, HAT6-based hole-transportation layer devices retain 93% of the initial efficiency for 690 h. Under continuous thermal stress of 85 degrees C, the devices based on HAT6 retain 95% of the initial PCE. The results demonstrate the time applicability of liquid crystal for stable PSCs fabrication.

WILEY-V C H VERLAG GMBH2023

C-60 Thin Films in Perovskite Solar Cells: Efficient or Limiting Charge Transport Layer?

Cansu Igci, Hiroyuki Kanda, Nadja Isabelle Desiree Klipfel, Mohammad Khaja Nazeeruddin, Cristina Roldán Carmona, Albertus Adrian Sutanto

In this work, we identify the importance of C-60 and compact-TiO2 (cTiO(2)) as electron transport layers on the device performance of coevaporated n-i-p perovskite solar cells. We found (1) a synergetic effect between both layers when extracting the charges and (2) that optimization of the C-60 layer is essential for obtaining devices with enhanced device performance. In particular, we found that a C-60 layer of an optimum thickness (20 nm), an additional charge transport resistance is observed by impedance analysis, indicating that devices with nonoptimized C-60 thickness could limit the fabrication of highly efficient perovskite solar cells.

AMER CHEMICAL SOC2022

Employing 2D-Perovskite as an Electron Blocking Layer in Highly Efficient (18.5%) Perovskite Solar Cells with Printable Low Temperature Carbon Electrode

Dmitry Bogachuk, Hiroyuki Kanda, Hobeom Kim, Mohammad Khaja Nazeeruddin, So-Min Yoo

Interface engineering and passivating contacts are key enablers to reach the highest efficiencies in photovoltaic devices. While printed carbon-graphite back electrodes for hole-transporting material (HTM)-free perovskite solar cells (PSCs) are appealing for fast commercialization of PSCs due to low processing costs and extraordinary stability, this device architecture so far suffers from severe performance losses at the back electrode interface. Herein, a 2D perovskite passivation layer as an electron blocking layer (EBL) at this interface to substantially reduce interfacial recombination losses is introduced. The formation of the 2D perovskite EBL is confirmed through X-ray diffraction, photoemission spectroscopy, and an advanced spectrally resolved photoluminescence microscopy mapping technique. Reduced losses that lead to an enhanced fill factor and V-OC are quantified by electrochemical impedance spectroscopy and J(SC)-V-OC measurements. This enables reaching one of the highest reported efficiencies of 18.5% for HTM-free PSCs using 2D perovskite as an EBL with a significantly improved device stability.

WILEY-V C H VERLAG GMBH2022

Exploring pi-extended subporphyrinoids as electron transporting materials in perovskite solar cells

Hiroyuki Kanda, Mohammad Khaja Nazeeruddin

Due to their strong acceptor properties and enhanced charge transport capabilities, non-fullerene electron acceptors based on pi-extended derivatives - subnaphthalocyanines (SubNc) or subphtalocyanine dimers (SubPc(2)) - have been employed in organic photovoltaics in the past as an alternative to the expensive fullerene. However, these promising pi-extended derivatives have not been explored in perovskite solar cell technology. In this work, we implement a vacuum-deposited very thin film of SubNc or SubPc(2) as electron transport layers in perovskite solar cells. In particular, we demonstrate the excellent electron extraction properties of the thin films in contact with perovskite layer. The fabricated perovskite solar cells exhibit enhanced device performances with reduced hysteresis index and improved device stability. Our results validate the use of n-extended subporphyrinoids as promising candidates for perovskite optoelectronics with enhanced stability properties, being essential for further conunercialization of the perovskite technology.

WORLD SCIENTIFIC PUBL CO PTE LTD2022

Modulating the Electron Transporting Properties of Subphthalocyanines for Inverted Perovskite Solar Cells

Hiroyuki Kanda, Mohammad Khaja Nazeeruddin

The lack of organic non-fullerene ETMs with good electron transport and device stability is an important problem for the further development and commercialization of perovskite solar cells. Herein, the use of SubPcs as ETMs in PSCs is explored. To this end, we analyze the influence of SubPc peripheral functionalization on the efficiency and stability of p-i-n PSCs. Specifically, ETMs based on three SubPcs (with either six or twelve peripheral fluorine and chlorine atoms) have been incorporated into PSCs with the perovskite layer deposited by solution processing (CsFAMAPbIBr). The device performance and morphology of these devices are deeply analyzed using several techniques, and the interfacial effects induced by the SubPcs are studied using photoluminescence and TR-PL. It is observed that the device stability is significantly improved upon insertion the SubPc layer. Moreover, the impact of the SubPc layer-thickness is assessed. Thus, a maximum power conversion efficiency of 13.6% was achieved with the champion device.

FRONTIERS MEDIA SA2022

Molecular Engineering of Fluorene-Based Hole-Transporting Materials for Efficient Perovskite Solar Cells

Hiroyuki Kanda, Nadja Isabelle Desiree Klipfel, Mohammad Khaja Nazeeruddin, Albertus Adrian Sutanto

New Spiro-OMeTAD analogues and the simpler "half" structures with the terminated methoxyphenyl and/or carbazolyl chromophores are successfully synthesized under Hartwig-Buchwald amination conditions using commercially available starting materials. New fluorene-based hole-transporting materials combined with suitable ionization energies properly align with the valence band of the perovskite absorber. Additionally, these compounds are amorphous, which is an advantage for the formation of homogenous films, as well as eliminate the possibility for films to crystallize during operation of the devices. The most efficient perovskite solar cells devices contain carbazolyl-terminated SpiroOMeTAD analogue V1267 and reach a power conversion efficiency of 18.3%, along with a short-circuit current density, open-circuit voltage, and fill factor of 23.41mA cm(-2), 1.06 V, and 74.0%, respectively. Moreover, "half" structures with methoxyphenyl/carbazolyl fragments show excellent long-term stability and outperform Spiro-OMeTAD and, therefore, hold a great prospect for practical wide-scale applications in optoelectronic devices.

WILEY-V C H VERLAG GMBH2022

Structural and photophysical investigation of single-source evaporation of CsFAPbI(3) and FAPbI(3) perovskite thin films

Hiroyuki Kanda, Nadja Isabelle Desiree Klipfel, Mohammad Khaja Nazeeruddin, Albertus Adrian Sutanto

Thermal vacuum deposition is a stimulating technique for upscaling perovskite solar cells. However, the operational complexity of multisource vapor deposition (MSVD) and achieving stoichiometric perovskite layers may impede its implementation. The single-source vapor deposition (SSVD) method has recently emerged as an alternative for MSVD due to its inherent functionality and ease of operation. Here, for the first time, we demonstrate a successful SSVD approach for fabricating pure CsFAPbI(3) and FAPbI(3) thin films from pre-synthesized perovskite powders. We carried out structural and photophysical investigations to optimize the phase purity and shelf-life of the deposited thin films. Furthermore, we probed the perovskite layer compatibility with various underlayers; we noted that MeO-2PACz, an organic underlayer, displayed superiority over other organic underlayers such as Spiro-OMeTAD and TaTm, and the SnO2 metal oxide layer, which might indicate that this method is more suitable for p-i-n solar cell fabrication. Our approach presents a straightforward methodology and avoids the use of multiple thermal sources to deposit CsFAPbI(3) and can further ease the vacuum deposition methodology.

ROYAL SOC CHEMISTRY2022

Zn(II) and Cu(II) tetrakis(diarylamine)phthalocyanines as hole-transporting materials for perovskite solar cells

Cansu Igci, Hiroyuki Kanda, Nadja Isabelle Desiree Klipfel, Wei Li, Mohammad Khaja Nazeeruddin, Kasparas Rakstys, Jianxing Xia

Finding new hole-transporting materials (HTMs) suitable for replacing the state-of-the-art spiro-OMe-TAD is still challenging. In this work, newly synthesized diarylamine-substituted metal phthalocyanines (MPcs, M 1/4 Zn(II) or Cu(II)) functionalized with either linear or branched alkoxy chains are evaluated as HTMs in perovskite solar cells. Both the nature of the alkoxy chains and that of the coordinated metal species were found to influence the functional properties of the new MPcs. In particular, devices based on a ZnPc featuring four n-butoxy side chains exhibited the highest power conversion efficiencies (PCEs). A PCE of 20.00% was reached for triple cation perovskite devices, and a PCE up to 20.18% could be achieved for double cation devices. (C) 2022 The Authors. Published by Elsevier Ltd.

ELSEVIER SCI LTD2022