Nanowelded carbon-nanotube-based solar microcells

A directed array of monolayer single-walled carbon nanotube (SWNTs) was nanowelded onto two asymmetrical metal electrodes with high and low work functions, resulting in a strong built-in electric field for efficient separation of photogenerated electron-hole pairs. Using standard UV lithography and lift-off process, the two metals were patterened by the overlay on silicon wafers with a 500-nm thermally oxidized layer forming the parallel electrode pairs. A 200 nm thick Al electrode was sputtered on the back of Si substrate, through which a gate voltage was supplied to the Si substrate for modulating the SWNT metal contact barrier. The SWNTs synthesized by the catalytic chemical vapor deposition (CVD) method with an average diameter of 0.9nm were dispersed fully in chloroform and aligned onto the source and drain electrodes by an AC dielectrophoresis method to form the dispersed parallel SWNT bundle array. It was found that the call can be effectively enhanced with the increase of the illumination power density.