Sputtered transparent electrodes for optoelectronic devices: Induced damage and mitigation strategies

Optoelectronic devices, such as solar cells and light-emitting diodes, well transparent electronic rely on efficient light–matter interactions usually require top electrodes that are deposited onto a device layer stack. Magnetron sputtering, established in the coating industry, is most common technique to deposit materials. Nevertheless, this process may result irreversible damage underlying sensitive layers because deposition involves high-energy particles plasma emission. Several strategies available prevent damage; some of these methods for various optoelectronic while others have yet be considered specific applications. Taking inspiration across different research fields, we discuss how choose adequate buffer devices possible paths eliminate their need via soft-landing electrodes. Transparent metal contacts by magnetron sputtering find applications numerous state-of-the-art diodes. However, thin films due emission particle impact. Inserting shield against mitigation approach. We start review describing sputtered become archetypal broad range then detrimental consequences sputter performance. Next, buffer-layer materials view processing-property-performance relationship. Finally, requirement implementing alternative, techniques Our highlights critical issue formulates strategies, provides cross-field learnings can lead more reliable aimed commercialization. IntroductionOptoelectronic diodes (LEDs), ubiquitous modern society.1Kasap S. Capper P. Edition. Springer Handbook Electronic Photonic Materials. 2. International Publishing, 2017Google Scholar Such typically consist photoactive material, sandwiched between an electron transport (ETL) hole (HTL), two outer electrodes, which at least front electrode highly transparent.2Liu L. Cao K. Chen Huang W. Toward see-through optoelectronics: cells.Adv. Opt. 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This, however, sophistication even replacement provide outlook further developing process-sensitive layers.Transparent requirements devicesIn top-emitting (or upwards-emitting) LEDs, ideal must effectively extract inject charges exhibiting minimal losses. Independent application, all should combine (1) spectral absorption device, (2) lateral (3) low-resistance Ohmic adjacent (4) stability, (5) low impact layers. Specifically, TCO capping stack improve protection moisture ingress.18Zhang Zhang Jiang Barrier designs long-term stability.Adv. 10: 2001610https://doi.org/10.1002/aenm.202001610Crossref To better understand necessity accomplish criteria, section first discusses formation level. Here, give nonexhaustive description perspective robustness relation. 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Due use challenges regarding damage, focus rest comparison summarized Table 1.Table 1Comparison devicesMaterialsDevice applicationsDeposition methodsBenefitsDrawbacksTCOssilicon , PSCs, OSCs, LEDssputtering, PLDaPulsed laser deposition., CVDbChemical ALDcAtomic processinglow resistivity fabrication, stabilityexpensive, TCOs: underneath, in-based scarcity indiumcarbon nanotubesPSCs, OSCssolution transfer, CVDhigh costexpensive, limited dispersibility, stabilitygraphene sheetsPSCsCVD, techniqueshigh transparencylow work function, doping uniformity areasthin filmsLEDs, OSCsevaporation, sputteringsimple processtrade-off sputtered: underneathmetal nanowiresPSCs, processinggood conductivityhigh roughness, adhesion, resistancedielectric/metal/dielectric multilayersPSCs, LEDsEvaporationgood flexibilitydemanding precise stack, interlayer filmsconductive polymersOSCs, LEDssolution processing, CVDlow cost, conductorshygroscopic nature, stabilitya Pulsed deposition.b Chemical deposition.c Atomic deposition. Open table new tab Origins TCOsTo identify root incurred working mechanism understood. Elaborate descriptions processes found dedicated literature;34Ellmer Welzel Reactive films: role energetic (ion) bombardment.J. 27: 765-779https://doi.org/10.1557/jmr.2011.428Crossref (91) 35Welzel Ellmer Negative oxygen reactive oxides.J. Vacuum 30: 061306https://doi.org/10.1116/1.4762815Crossref (32) 36Ellmer discharges deposition.in: Hippler Kersten Schmidt Schoenbach K.H. Low Temperature Plasmas. Fundamentals, Technologies Techniques. Wiley-VCH, 2008: 675-715Google 37Lieberman M.A. Lichtenberg A.J. Principles Plasma Discharges Processing.2nd John Wiley & Sons, 2005Crossref here briefly summarize main principles method relevance Sputtering nonthermal, plasma-assisted (PVD) ejecting atoms molecules bulk (cathode) substrate (anode) momentum caused bombardment plasma-excited Ar ions). performed low-pressure (<5 mammalian rapamycin) suffer negligible gas-phase collisions. ejected directed form film, sketched Figure 1. discharge sustained vicinity magnetic confinement electrons. contrast electrons, ions neutral barely influenced field.19Ramírez ScholarThe voltages −200 −800 V will depend desired conditions configuration system. Usually, RF DC (deposition TCOs). Notably, magnitude voltage linked level application help minimize damage.36Ellmer Scholar,38Jagt R.A. Huq T.N. Hill S.A. Thway Napari Roose Gałkowski Lin S.F. al.Rapid vapor-phase p-type photovoltaics devices.ACS 2456-2465https://doi.org/10.1021/acsenergylett.0c00763Crossref (11) ScholarSputter attributed substrate's species. elaborate discussion influence Welzel.34Ellm