Theory of Tribovoltaics: Direct Current Generation at a p - n Semiconductor Interface

A simple theory of tribovoltaics is proposed by using a quantum mechanical model of energy release due to sliding-induced bonding between the surfaces of a <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mi>p</a:mi></a:math>-doped semiconductor and a <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:mi>n</d:mi></d:math>-doped semiconductor. The energy release in forming a bond may lead to the excitation of electron-hole pairs at the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><g:mi>p</g:mi></g:math>-<j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><j:mi>n</j:mi></j:math> semiconductor interface if the released energy is higher than the effective band gap at the semiconductor interface. An expression for the generated current as a function of the relative sliding speed between the <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><m:mi>p</m:mi></m:math> and <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><p:mi>n</p:mi></p:math> sides is suggested and used to model current transport by solving the complete set of drift-diffusion equations with appropriate boundary and initial conditions. Analytical results are obtained and verified numerically using the finite-element-method software. It is shown that since the typical time period associated with periodic sliding is many orders of magnitude higher than the carrier lifetimes, the time-dependent variations in the electron and hole concentrations and the current density follow the time variation of the sliding speed. Since the electron-hole pair generation occurs near the semiconductor interface only, the current density is shown to be constant as a function of position even if the sliding speed changes in time. Published by the American Physical Society 2024