Application of low-cost MWCNT/polymer based heating elements as room temperature NIR bolometers with high signal to noise ratio

Multi-walled carbon nanotube networks have been demonstrated to enable the realization of flexible and low-cost electrical heaters, often combined with interesting sensing properties. In order to enhance the stability they are often embedded into a polymeric or epoxy matrix material, that on the other hand strongly modifies the actuating and sensing properties [1,2,3]. One of the most promising applications of nanotube networks in optoelectronic applications, besides their use as hetero-emitters and transparent conducting contacts in solar cells, is their application as sensitive bolometers without need of external cooling. While in the case of single-walled carbon nanotubes even wavelength selective bolometers can be realized [4], multi-walled carbon nanotube based bolometers have generally demonstrated a higher sensitivity and also a faster response [5]. A series of very common nanocomposite based electrical heaters have been investigated regarding their room-temperature bolometer functionality in the near-infrared wavelength range. In particular devices with syndiotactic polystyrene, high-density polyethylene and epoxy resin as matrix materials, all realized with the same type of MWCNT filler, have been investigated. First of all, we obtained - with the appropriate contact material - in all cases a perfectly linear current-voltage characteristics and very good room-temperature conductivity stability. In the case of the polystyrene based nanocomposite material, however, this had only be achieved after a prior Joule heating burn-in procedure. Using LEDs at 780nm and 1300nm for excitation we could for all three materials demonstrate linear, with respect to the light intensity, bolometer operation with good long-term stability and a very good signal-to-noise ratio.