Perovskite and organic solar cells fabricated by inkjet printing: progress and prospects

Inkjet printing (IJP) technology, adapted from home and office printing, has proven to be an essential research tool and industrial manufacturing technique in a wide range of printed electronic technologies, including optoelectronics. Its primary advantage over other deposition methods is the low-cost and maskless on-demand patterning, which offers unmatched freedom-of-design. Additional benefits include the efficient use of materials, contactless high-resolution deposition, and scalability, enabling rapid translation of learning from small-scale, laboratory-based research into large-scale industrial roll-to-roll manufacturing. In the development of organic solar cells (OSCs), IJP has enabled the printing of many of the multiple functional layers which comprise the complete cell as part of an additive printing scheme. Although IJP is only recently employed in perovskite solar cell (PeSC) fabrication, it is already showing great promise and is anticipated to find broader application with this class of materials. As OSCs and PeSCs share many common functional materials and device architectures, this review presents a progress report on the IJP of OSCs and PeSCs in order to facilitate knowledge transfer between the two technologies, with critical analyses of the challenges and opportunities also presented

Dipole-field-assisted charge extraction in metal-perovskite-metal back-contact solar cells

Hybrid organic-inorganic halide perovskites are low-cost solution-processable solar cell materials with photovoltaic properties that rival those of crystalline silicon. The perovskite films are typically sandwiched between thin layers of hole and electron transport materials, which efficiently extract photogenerated charges. This affords high-energy conversion efficiencies but results in significant performance and fabrication challenges. Herein we present a simple charge transport layer-free perovskite solar cell (PSC), comprising only a perovskite layer with two interdigitated gold back-contacts. Charge extraction is achieved via self-assembled molecular monolayers (SAMs) and their associated dipole fields at the metal/perovskite interface. Photovoltages of approximately 600 mV generated by SAM-modified PSCs are equivalent to the built-in potential generated by individual dipole layers. Efficient charge extraction results in photocurrents of up to 12.1 mA/cm2 under simulated sunlight, despite a large electrode spacing.Comment: 18 pages, 5 figure

Can Laminated Carbon Challenge Gold? Toward Universal, Scalable, and Low-Cost Carbon Electrodes for Perovskite Solar Cells

While perovskite solar cell (PSC) efficiencies are soaring at a laboratory scale, these are most commonly achieved with evaporated gold electrodes, which would present a significant expense in large-scale production. This can be remedied through the use of significantly cheaper carbon electrodes that, in contrast to metals, also do not migrate through the device. To this end, the present work investigates simple-to-prepare aluminum-supported carbon electrodes derived from commercially available, inexpensive materials that can be applied onto various hole-transporting materials and enable photovoltaic performances on par with those provided by gold electrodes. Successful integration of the new carbon-based electrode into flexible devices produced by a roll-to-roll printing technology by both pressing and lamination is demonstrated. However, temperature cycling durability tests reveal that the use of carbon electrodes based on commercial pastes is hindered by incompatibility of adhesive additives with the key components of the PSCs under heating. Resolving this issue, tailor-made graphite electrodes devoid of damaging additives are introduced, which improve the PSC stability under temperature cycling test protocol to the level provided by benchmark gold electrodes. The study highlights current challenges in developing laminated carbon electrodes in PSCs and proposes strategies toward the resolution thereof.This work was funded by the Australian Centre for Advanced Photovoltaics and Australian Renewable Energy Agency. A.N.S. also acknowledges the financial support from the Australian Research Council (Centre of Excellence CE140100012; Future Fellowship FT200100317). Monash Centre for Electron Microscopy (MCEM) and Melbourne Centre for Nano fabrication (MCN) are acknowledged for providing access to their facilities. The authors are grateful to Dr T. Zhang, A. Surmiak, Dr. N. Peris, Dr. D. Senevirathna, and Dr. N. Pai from Monash University for the experimental support throughout this study

One-step Preparation of ZnO Electron Transport Layers Functionalized with Benzoic Acid Derivatives

We present a "one-step" approach to modify ZnO electron transport layers (ETLs) used in organic solar cells. This approach involves adding benzoic acid (BZA) derivatives directly to the ZnO precursor solution, which are then present at the surface of the resulting ZnO film. We demonstrate this approach for three different BZA derivatives, namely benzoic acid, chlorobenzoic acid, and 4-hydrazinobenzoic acid. For all molecules, improved device performance and stability is demonstrated in solar cells using an active layer blend of PTQ10 (donor) and ITIC-Br (non-fullerene acceptor) compared to such cells prepared using untreated ZnO. Furthermore, similar or improved device performance and stability is demonstrated compared to conventional PEIE treatment of ZnO. The presence of the BZA derivatives at the surface after processing is established using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine-structure spectroscopy. From atomic force microscopy analysis and X-ray diffraction studies, the addition of BZA derivatives appears to restrict ZnO grain growth; however, this does not negatively impact device performance. ZnO layers treated with BZA derivatives also exhibit higher water contact angle and lower work function compared to untreated ZnO. This approach enables simplification of device manufacture while still allowing optimization of the surface properties of metal oxide ETLs. Keywords: electron transport layers, zinc oxide, organic solar cells, surface modificationComment: Manuscript: 25 pages, 8 figures, 5 tables. Supplementary Material: 36 pages, 22 figures, 13 tables. Submitted to Solar Energy Materials and Solar Cell

Solution processable direct bandgap copper-silver-bismuth iodide photovoltaics : compositional control of dimensionality and optoelectronic properties

Altres ajuts: SRR acknowledges the support from "laCaixa" Foundation (ID 100010434; LCF/BQ/PI20/11760024). Open access publishing facilitated by Monash University, as part of the Wiley - Monash University agreement via the Council of Australian University Librarians.The search for lead-free alternatives to lead-halide perovskite photovoltaic materials resulted in the discovery of copper(I)-silver(I)-bismuth(III) halides exhibiting promising properties for optoelectronic applications. The present work demonstrates a solution-based synthesis of uniform CuAgBiI thin films and scrutinizes the effects of x on the phase composition, dimensionality, optoelectronic properties, and photovoltaic performance. Formation of pure 3D CuAgBiI at x = 1, 2D CuAgBiI at x = 2, and a mix of the two at 1 < x < 2 is demonstrated. Despite lower structural dimensionality, CuAgBiI has broader optical absorption with a direct bandgap of 1.89 ± 0.05 eV, a valence band level at -5.25 eV, improved carrier lifetime, and higher recombination resistance as compared to CuAgBiI. These differences are mirrored in the power conversion efficiencies of the CuAgBiI and CuAgBiI solar cells under 1 sun of 1.01 ± 0.06% and 2.39 ± 0.05%, respectively. The latter value is the highest reported for this class of materials owing to the favorable film morphology provided by the hot-casting method. Future performance improvements might emerge from the optimization of the CuAgBiI layer thickness to match the carrier diffusion length of ≈40-50 nm. Nonencapsulated CuAgBiI solar cells display storage stability over 240 days

Balancing charge extraction for efficient back-contact perovskite solar cells by using an embedded mesoscopic architecture

As the performance of organic–inorganic halide perovskite solar cells approaches their practical limits, the use of back-contact architectures, which eliminate parasitic light absorption, provides an effective route toward higher device efficiencies. However, a poor understanding of the underlying device physics has limited further performance improvements. Here a mesoporous charge-transporting layer is introduced into quasi-interdigitated back-contact perovskite devices and the charge extraction behavior with an increased interfacial contact area is studied. The results show that the incorporation of a thin mesoporous titanium dioxide layer significantly shortens the charge-transfer lifetime and results in more efficient and balanced charge extraction dynamics. A high short-circuit current density of 21.3 mA cm–2 is achieved using a polycrystalline perovskite layer on a mesoscopic quasi-interdigitated back-contact electrode, a record for this type of device architecture.The authors are grateful for the financial support by the Australian Centre for Advanced Photovoltaics (ACAP), the Australian Renewable Energy Agency (ARENA), and the Australian Research Council (ARC) ARC Centre of Excellence in Exciton Science (ACEx: CE170100026). This work was performed in part at the Melbourne Centre for Nanofabrication (MCN) in the Victorian Node of the Australian National Fabrication Facility (ANFF). Q.O. acknowledges the support from the ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET).Peer reviewe

Back-contact perovskite solar cell fabrication via microsphere lithography

Back-contact electrodes for hybrid organic-inorganic perovskite solar cells (PSCs) eliminate the parasitic absorption losses caused by the transparent conductive electrodes that are inherent to conventional sandwich-architecture devices. However, the fabrication methods for these unconventional architectures rely heavily on expensive photolithography, which limits scalability. Herein, we present an alternative cost-effective microfabrication technique in which the conventional photolithography process is replaced by microsphere lithography in which a close-packed polystyrene microsphere monolayer acts as the patterning mask for the honeycomb-shaped electrodes. A comprehensive comparison between photolithography and microsphere lithography fabrication techniques was conducted. Using microsphere lithography, we achieve highly efficient devices having a stabilized power conversion efficiency (PCE) of 8.6%, twice the reported value using photolithography. Microsphere lithography also enabled the fabrication of the largest back-contact PSC to date, having an active area of 0.75 cm2 and a stabilized PCE of 2.44%.This work was financially supported by the Australian Government through the Australian Renewable Energy Agency (ARENA) the Australian Centre for Advanced Photovoltaics (ACAP) and the Australian Research Council (ARC, DE220100154). This work was performed in part at the Melbourne Centre for Nanofabrication (MCN) in the Victorian Node of the Australian National Fabrication Facility (ANFF). The authors acknowledge use of facilities within the Monash Centre for Electron Microscopy (MCEM). The authors acknowledge use of facilities within the Flexible Electronics Laboratory (FEL) at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Clayton site. S.R.R. acknowledges the support from “la Caixa” Foundation (ID 100010434). Fellowship code LCF/BQ/PI20/11760024.Peer reviewe

Metal complexes containing dicyanonitrosomethanide and its derivatives

This thesis examines the chemistry of the dicyanonitrosomethanide (dcnm) anion and how it may undergo the transition metal promoted addition of a nucleophile as a means of in situ ligand formation. A computational study indicated that the addition of water to a nitrile group of the dcnm anion only gives the anti-isomer of the carbamoylcyanonitrosomethanide (ccnm) anion, with the syn isomer resulting from the subsequent rotation of the nitroso group of the anti-isomer. The addition of a molecule of water to the ccnm or dicyanonitromethanide (dcnom) anions was not experimentally observed, and appears electronically disfavoured. The in situ transition metal promoted additions of ethanol, n-propanol and ethylene glycol methyl ether to the dcnm anion were observed for the first time, with the presence of ammonia causing the deprotonation of the ccnm anion to give the dianionic amidocarbonyl(cyano)nitrosomethanide species. The reaction path for the addition and subsequent cyclisation of two molecules of 1,2-diaminoethane to the dcnm anion to give the di(imidazolinyl)nitrosomethanide (dinm) ligand has been deduced. Ethanolamine was shown to add to the dcnm anion via the NH2 moiety, demonstrating higher reactivity of amines than alcohols in transition metal promoted reactions with the dcnm anions. Coordinatively divergent derivatives of the dcnm anion in conjunction with bridging co-ligands give a range of topologically diverse coordination polymers. The facile loss of methanol molecules residing in the lattice of a 1D coordination polymer results in its transformation into a 3D network. The nitroso group has proven to be ideal for bridging between metal centres to aid in the formation of polynuclear homometallic complexes, with these clusters predominantly displaying antiferromagnetic coupling. An octanuclear dysprosium cluster displayed behaviour indicative of slow magnetisation reversal. The heterofunctionalised nature of derivatives of dcnm makes them ideal for forming 3d/4f heterobimetallic clusters such as [{Gd(OH)(ccnm)2(H2O)4}2MnIII](ClO4)3 and [Ln2MnIII2O2(ccnm)6(dcnm)2(H2O)2]. The viability of using the carbonate anion of as a cluster forming agent has been demonstrated during the synthesis of the polynuclear complexes [Ln13(H2O)6(phen)18(ccnm)6(CO3)14]•Cl3•CO3 (Ln = La, Ce, Pr) and [Gd14(CO3)13(ccnm)9(OH)(H2O)6(phen)13(NO3)](CO3)2.5•phen. In the homoleptic 12-coordinate complex [Ln(ccnm)6]3− there is strong intramolecular hydrogen bonding between the nitroso and carbamoyl groups of adjacent ligands. The use of the dcnm ligand results in the formation of an analogous trianionic lanthanoid complex. The presence of intra- and intermolecular hydrogen bonding and sterically crowding co-ligands have been used to probe the nature of the nitroso groups of dcnm and ccnm ligands coordinating to lanthanoids. The [Ln(dcnm)6]3− trianion has been incorporated into a range of ionic liquids (ILs). The use of counter-cations that may act as hydrogen bond donors resulted in an increase in the melting points of the ILs. Synchrotron based in situ powder diffraction studies were used to determine that the observed change in the melting point of complexes [N4444]3[Ln(dcnm)6] over several heating and cooling cycles was due to the recrystallisation of the product giving a less thermodynamically stable polymorph. <div><br></div><div>Awards: Winner of the Mollie Holman Doctoral Medal for Excellence, Faculty of Science, 2011.</div