Diffraction Characteristics of 3-Dimensional Wrinkles and Folds

Abstract

Three-dimensional (3D) wrinkles and folds as periodic structures allow us to improve optical and mechanical characteristics of various optoelectronic devices by controlling light propagation or by inducing stress release capability into optoelectronic devices. Here, I explore visible light diffraction by 3D wrinkles and folds with different wrinkle wavelengths and fold fractions, expecting to increase their applicability for optoelectronic devices, especially where visible light (wavelength: 400 similar to 700 nm) is most important, such as organic light emitting diodes (OLED) and organic solar cells (OSC). Contrary to unidirectional periodic structures, 3D wrinkles and folds generated diffraction rings instead of diffraction spots due to their directional randomness. Moreover, when increasing wrinkle wavelength, diffraction angle decreased and diffraction efficiency increased. Maximum diffraction efficiency achieved in this study was about 25%. Then, introducing folds into wrinkle surfaces induced additional diffraction rings with small diffraction angle, indicating folds also have periodicity. The periodicity generated by folds was 8.4-12.7 mu m, depending on the fold fraction.