Exploring the degradation of silver nanowire networks under thermal stress by coupling in situ X-ray diffraction and electrical resistance measurements
Résumé
The thermal instability of silver nanowires (AgNWs) leads to a significant
increase of the electrical resistance of AgNW networks. A
better understanding of the relationship between the structural
and electrical properties of AgNW networks is primordial for their
efficient integration as transparent electrodes (TEs) for next-generation
flexible optoelectronics. Herein, we investigate the in situ
evolution of the main crystallographic parameters (i.e. integrated
intensity, interplanar spacing and peak broadening) of two Ag specific
Bragg peaks, (111) and (200), during a thermal ramp up to
400 °C through in situ X-ray diffraction (XRD) measurements,
coupled with in situ electrical resistance measurements on the
same AgNW network. First, we assign the (111) and (200) peaks of
χ-scans to each five crystallites within AgNWs using a rotation
matrix model. Then, we show that the thermal transition of bare
AgNW networks occurs within a temperature range of about 25 °C
for the electrical properties, while the structural transition spans
over 200 °C. The effect of a protective tin oxide coating (SnO2) on
AgNW networks is also investigated through this original in situ
coupling approach. For SnO2-coated AgNW networks, the key XRD
signatures from AgNWs remain constant, since the SnO2 coating
prevents Ag atomic surface diffusion, and thus morphological
instability (i.e. spheroidization). Moreover, the SnO2 coating does
not affect the strain of both (111) and (200) planes. The thermal
expansion for bare and SnO2-coated AgNW networks appears very
similar to the thermal expansion of bulk Ag. Our findings provide
insights into the underlying failure mechanisms of AgNW networks
subjected to thermal stress, helping researchers to develop more
robust and durable TEs based on metallic nanowire networks.