Direct Current Nanogenerator Based on Tribovoltaic\nEffect at WS₂ Semiconductor Interface

Abstract

With\nthe fast development of microelectronic devices and the Internet\nof Things, triboelectric nanogenerators (TENGs) have been widely explored\nin self-powered micro/nano electronic devices recently. However, there\nare still many limitations for direct current (DC) TENGs. This study\ndeveloped a semiconductor DC tribovoltaic nanogenerator (SDC-TVNG)\nbased on n-type WS₂ and p-type silicon (p-Si). Unlike alternating\ncurrent output in contact-separation mode, the current generated during\nhorizontal sliding friction, regardless of the sliding direction and\nwhether it was positive or negative, was a DC signal from p-Si to\nn-type WS₂. We studied the influence of frictional characteristics\non the electrical output and found that the normal pressure and motion\nfrequency had a positive correlation with the size of the DC signal.\nThe maximum short-circuit current was 0.01 μA at a frequency\nof 1 Hz and a normal pressure of 10 N. The SDC-TVNG achieved a maximum\npower density of 2.46 μW/m² at an outer impedance\nof 40 MΩ. Particularly, the tribovoltaic effect at the semiconductor–liquid–semiconductor\ninterface was explored. Since the filled liquid layer could eliminate\nthe insufficiency and uncertainty of the semiconductor–semiconductor\ncontact friction, the maximum DC output of the semiconductor–liquid–semiconductor\nDC tribovoltaic nanogenerator (SLSDC-TVNG) was increased to 4.2 μA\nby a factor of 142 as compared to the current of 0.03 μA without\nadding the liquid (100 g/L NaCl solution) layer. The maximum power\ndensity of the device was 5.09 μW/m² with a DC of\n0.02 μA when the external resistance was 40 MΩ. This increased\ntribovoltaic nanogenerator with surface states at semiconductor interfaces,\na composite system coupled by the liquid-enhancement effect and the\ntribovoltaic effect, promotes the separation of electron–hole\npairs and the enhancement of current output.