Tensile Mechanical Strain Effects on the Electrical Characteristics of Roll-to-Roll Printed OSC

Abstract

In this article, we have investigated the electrical characteristics alterations of an industrial roll-to-roll printed organic solar cell (OSC) in presence of tensile mechanical strain. The strain applied perpendicular to the electrodes axis and the changes in the device microstructure have been discussed. In order to study the residual effects of tensile strain on the OSC’s structure, the strain was applied up to 180 m <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$\epsilon$</tex></formula> in three consecutive days. At the third day of the experiment, we increased the tension up to 320 m <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$\epsilon$</tex></formula> . At each step of applying strain, I–V characteristics under illumination was extracted. The measurements show the increase in <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$I_{sc}$</tex></formula> , <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$V_{oc}$</tex></formula> , <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$FF$</tex></formula> , and <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$PCE$?</tex></formula> by 21%, 22.5%, 85%, and 24%, respectively, for the strain in range of 100 to 180 m <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$\epsilon$</tex></formula> . The enhancements are originated from increasing the crystallinity degree of the active-layer polymer in response to strain. Also, the strain reduced the device active material layer’s thickness that will provide a better overlap of <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$\pi$</tex></formula> orbitals wave function. Consequently, the charge transportation in the OSC advances. For tensile mechanical strain higher than 180 m <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$\epsilon$</tex></formula> the electrical characteristics declined. Layers delamination and crack propagation through the electrodes are the main reasons for the OSC degradation under the applied strain.