Daniel David Tune

This study presents a detailed evaluation of electrically conductive adhesives (ECAs) in photovoltaic (PV) modules, focusing on their impact on module power loss under standard accelerated aging conditions used in industry. The study was enabled by using an innovative analytical method to determine the contact resistivity of ECA‐based interconnects that was previously developed as part of this research and provides unique insights into ECA performance in PV modules. The findings reveal that interconnects based on epoxy‐ECA formulations tested in this experiment exhibit significant degradation in contact resistivity during damp heat and thermal cycling tests, whereas interconnects using acrylic‐ECA formulations demonstrate a more stable contact resistivity. Contrary to expectations, no strong correlation was observed between the contact resistivity degradation of ECA‐based interconnects and module power loss, challenging prevailing assumptions about module reliability. This suggests that other factors, such as cell metallization degradation, play a more critical role. Furthermore, encapsulation materials significantly influence module resilience, with the polyolefin elastomer formulation used in this study providing superior moisture protection for cells, while the ethyl vinyl acetate formulation offered better protection for interconnects. These insights underscore the complexities of module reliability, highlighting the need for innovative materials and enhanced testing protocols to ensure long‐term performance. © 2025 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Unassisted photoelectrochemical (PEC) reactions, such as H₂ generation and CO₂ reduction, are limited by the durability of the immersed photoelectrode. Small band gap semiconductors, like Si, are efficient at utilizing a large portion of the solar spectrum but are not stable in aqueous environments without protection. While great strides have been made to improve stability under constant illumination, dark stability remains relatively unexamined and presents great challenges for durable PEC systems. Cathodic protection is an established electrochemical method for preventing metal electrode degradation in harsh conditions. Similar protection strategies cannot be applied to traditional two-terminal (2T) semiconductor photoelectrodes because of their inability to pass reverse bias current in the dark. New, three-terminal (3T) photovoltaic (PV) architectures introduce additional degrees of freedom in traditional 2T PEC operations by adding an extra electrical contact for an alternative low resistance path to protect the photoelectrode and drive electrochemical reactions, even in the dark. Here, we investigate bare 3T Si PV devices operating as photocathodes in aqueous methyl viologen electrolyte. The 3T architecture provides additional capabilities to PEC systems such as cathodic protection, the ability to drive reactions with or without illumination, and in situ switching between different operational modes. We show that 3T-based Si photocathodes maintain PEC activity after several hours of light/dark cycling. This work helps advance PEC use in real-world conditions where variable illumination must be considered.

Our previous work highlighted how microscopic structural effects influence the sheet and contact resistance of electrically conductive adhesives (ECAs). Herein, we delve further by investigating how the contact and bulk resistivity of several ECAs that are based on the same formulation, but with different filler content, are correlated with the filler content. Additionally, two different filler geometries — high and low surface area (HSA and LSA) fillers — are combined in different ratios to maintain a similar viscosity and therefore processability. Hence, contact and bulk resistivities are also correlated with the different geometry ratios of these two fillers. As expected, it was found that the contact and bulk resistivities decreased when the filler content was increased. However, the magnitude of the decrease was found to depend strongly on the filler geometry ratio. At extreme filler geometry ratios, when the bulk is either mostly loaded with HSA‐fillers or mostly with LSA‐fillers, the impact of changes in the filler content on the bulk and contact resistivities is markedly different. The measured data is interpreted within the context of percolation theory and it is determined that the optimum ratio of the LSA and HSA Ag‐fillers investigated in this study is approximately 60:40 (for an epoxy‐based adhesive). This work has important ramifications for the design of ECAs, where cost considerations and the need to reduce silver resource usage demand the lowest (silver) filler content, but the demands of product performance point to higher filler content.

Phosphorene nanoribbons (PNRs) have been widely predicted to exhibit a range of superlative functional properties; however, because they have only recently been isolated, these properties are yet to be shown to translate to improved performance in any application. PNRs show particular promise for optoelectronics, given their predicted high exciton binding energies, tunable bandgaps, and ultrahigh hole mobilities. Here, we verify the theorized enhanced hole mobility in both solar cells and space-charge-limited-current devices, demonstrating the potential for PNRs improving hole extraction in universal optoelectronic applications. Specifically, PNRs are demonstrated to act as an effective charge-selective interlayer by enhancing hole extraction from polycrystalline methylammonium lead iodide (MAPbI₃) perovskite to the poly(triarylamine) semiconductor. Introducing PNRs at the hole-transport/MAPbI₃ interface achieves fill factors above 0.83 and efficiencies exceeding 21% for planar p–i–n (inverted) perovskite solar cells (PSCs). Such efficiencies are typically only reported for single-crystalline MAPbI₃-based inverted PSCs. Methylammonium-free PSCs also benefit from a PNR interlayer, verifying applicability to architectures incorporating mixed perovskite absorber layers. Device photoluminescence and transient absorption spectroscopy are used to demonstrate that the presence of the PNRs drives more effective carrier extraction. Isolation of the PNRs in space-charge-limited-current hole-only devices improves both hole mobility and conductivity, demonstrating applicability beyond PSCs. This work provides primary experimental evidence that the predicted superlative functional properties of PNRs indeed translate to improved optoelectronic performance.

The photonic post-processing of suspended carbon nanotube (CNT) ribbons made by floating catalyst chemical vapor deposition (FC-CVD) results in selective sorting of the carbon nanotubes present. Defective, thermally non-conductive or unconnected CNTs are burned away, in some cases leaving behind a highly crystalline (as indicated by the Raman G:D ratio), highly conductive network. However, the improvement in crystallinity does not always occur but is dependent on sample composition. Here, we report on fundamental features, which are observed for all samples. Pulse irradiation (not only by laser but also white light camera flashes, as well as thermal processes such as Joule heating) lead to (1) the sweating-out of catalyst nanoparticles resulting in molten catalyst beads of up to several hundreds of nanometres in diameter on the textile surface and (2) a significant improvement in CNT bundle alignment. The behavior of the catalyst beads is material dependent. Here, we show the underlying mechanisms of the photonic post-treatment by modelling the macro- and microstructural changes of the CNT network and show that it is mainly the amount of residual catalyst which determines how much energy these materials can withstand before their complete decomposition.

The latest advances in carbon nanotube–silicon heterojunction solar cells are combined with a new doping protocol based on the outstanding electron withdrawing properties and excellent silicon surface passivation ability of sulfonated polytetrafluoroethylene (Nafion). Using this new dopant for carbon nanotube–silicon solar cells, advanced substrate design, and an optimized antireflective texture fast etch with organic base, breakthrough performance is obtained from research grade devices with active areas of 1 and 5 cm², which yield power conversion efficiencies of 17.2 and 15.5%, respectively.