M. Ignacia Devoto Acevedo, Matthias Helbig, Karl Wienands, Andreas Halm, Daniel Tune
{"title":"Effect of carbon nanotubes in conductive adhesives for photovoltaics","authors":"M. Ignacia Devoto Acevedo, Matthias Helbig, Karl Wienands, Andreas Halm, Daniel Tune","doi":"10.1016/j.solmat.2025.113790","DOIUrl":null,"url":null,"abstract":"<div><div>This study investigated the impact of adding carbon nanotubes (CNTs) to silver-loaded epoxy-based adhesives, focusing on mechanical adhesion, electrical performance, and reliability. CNTs improve electrical conductivity in polymers by forming conductive networks with a low percolation threshold, requiring significantly lower filler loading compared to micron-sized fillers. In this study, a commercial electrically conductive adhesive (ECA) is modified by adding 0.05 to 0.63 wt% of CNTs and several dedicated test structures are manufactured with it. The samples are stressed up to 2000 h under damp-heat and up to 400 thermal cycles. The results indicate that CNTs enhance peel strength, but only above a threshold concentration, with a 0.19 wt% addition increasing adhesion by 82 %, while higher concentrations yield diminishing improvements. The electrical performance is influenced differently: the sheet resistivity of ECA (<em>R</em><sub><em>s</em></sub>) improves with increasing CNT content, whereas the contact resistivity (<em>ρ</em><sub><em>c</em></sub>) initially increases before decreasing with higher CNT concentration. Under thermal cycling, higher CNT content mitigates <em>R</em><sub><em>s</em></sub> degradation, with the 0.63 wt% CNT formulation exhibiting superior long-term stability, though <em>ρ</em><sub><em>c</em></sub> degrades in all cases. During damp-heat exposure, <em>R</em><sub><em>s</em></sub> improves over time, while <em>ρ</em><sub><em>c</em></sub> degrades with increasing stress duration. Interestingly, <em>R</em><sub><em>s</em></sub> and <em>ρ</em><sub><em>c</em></sub> exhibit opposing trends, suggesting minimal overall impact on module performance (for the particular bill of material used in this study). The study also highlights the challenge of isolating the effects of CNTs from epoxy dilution, emphasizing the need for better control of the ECA formulations. These findings demonstrate the potential of CNT-enhanced ECAs for improved adhesion and electrical stability in photovoltaic applications, provided that trade-offs in contact resistivity are carefully managed to ensure long-term reliability.</div></div>","PeriodicalId":429,"journal":{"name":"Solar Energy Materials and Solar Cells","volume":"292 ","pages":"Article 113790"},"PeriodicalIF":6.3000,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Solar Energy Materials and Solar Cells","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0927024825003915","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
This study investigated the impact of adding carbon nanotubes (CNTs) to silver-loaded epoxy-based adhesives, focusing on mechanical adhesion, electrical performance, and reliability. CNTs improve electrical conductivity in polymers by forming conductive networks with a low percolation threshold, requiring significantly lower filler loading compared to micron-sized fillers. In this study, a commercial electrically conductive adhesive (ECA) is modified by adding 0.05 to 0.63 wt% of CNTs and several dedicated test structures are manufactured with it. The samples are stressed up to 2000 h under damp-heat and up to 400 thermal cycles. The results indicate that CNTs enhance peel strength, but only above a threshold concentration, with a 0.19 wt% addition increasing adhesion by 82 %, while higher concentrations yield diminishing improvements. The electrical performance is influenced differently: the sheet resistivity of ECA (Rs) improves with increasing CNT content, whereas the contact resistivity (ρc) initially increases before decreasing with higher CNT concentration. Under thermal cycling, higher CNT content mitigates Rs degradation, with the 0.63 wt% CNT formulation exhibiting superior long-term stability, though ρc degrades in all cases. During damp-heat exposure, Rs improves over time, while ρc degrades with increasing stress duration. Interestingly, Rs and ρc exhibit opposing trends, suggesting minimal overall impact on module performance (for the particular bill of material used in this study). The study also highlights the challenge of isolating the effects of CNTs from epoxy dilution, emphasizing the need for better control of the ECA formulations. These findings demonstrate the potential of CNT-enhanced ECAs for improved adhesion and electrical stability in photovoltaic applications, provided that trade-offs in contact resistivity are carefully managed to ensure long-term reliability.
期刊介绍:
Solar Energy Materials & Solar Cells is intended as a vehicle for the dissemination of research results on materials science and technology related to photovoltaic, photothermal and photoelectrochemical solar energy conversion. Materials science is taken in the broadest possible sense and encompasses physics, chemistry, optics, materials fabrication and analysis for all types of materials.