PHOTOLUMINESCENT LIGHT SOURCE ARRAYS BY SINERGIC INTEGRATION OF CONJUGATED LUMINESCENT POLYMERS AND THREE-DIMENSIONAL SILICON MICROSTRUCTURES

In this work, a novel and straightforward technology for the fabrication of two-dimensional (2D) arrays of photolu-minescent light-sources by selective integration of conjugated luminescent polymers into three-dimensional (3D) silicon microstructures is presented [1]. Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) infiltration into 3D silicon microstructures integrating 2D arrays of square holes with different sizes, periods, and aspect ratios (ARs, hole depth-to-width ratio) is investigated by means of three different approaches, namely, spin-coating, dip-coating and drop-casting/slow solvent evaporation. The microstructure, which is fabricated by electrochemical mi-cromachining (ECM) technology [2], consists of a 2D array of 40-μm-side square holes with spatial periods of 70 μm integrated with a 2D array of 4-μm-side square holes with spatial periods of 10 μm. Both the arrays feature hole depths of about 50 μm, thus combining, on the same silicon die, low-AR holes (about 1) and high-AR holes (about 10). Notably, by properly choosing the deposition method, F8BT can be selectively infiltrated in either low- or high-AR holes. Fluorescence microscopy clearly highlights that each polymer-infiltrated hole behaves as a single light-source, due to the confinement effect exerted by the microstructure features on the polymer light-emission in the out-of-plane direction, independently of AR value, size and period. Such a synergic integration of luminescent pol-ymers and silicon microstructures paves the way for new exciting applications, ranging from photonics (e.g. flat panel displays) to medicine (e.g. label-free circulating tumor cell targeting).