ITO-free 3D MEMS photodetector for point-of-care biosensing devices

Organic Photo Detectors (OPD) present an attractive detection system to be incorporated in Point of Care (POC) disposable diagnostic devices due to their low cost fabrication and flexible device structure. Indium Tin Oxide (ITO) is the most commonly used material for the fabrication of transparent anode for these devices. The fabrication of ITO is an expensive process and the rarity of the materials required itself makes this the cost driving factor in realizing cheap and hence disposable detection system for the POC devices. Furthermore ITO has a spiked morphology that results in a shorter device lifetime. All these disadvantages associated with ITO have made the search for an alternative material for ITO which has comparable characteristics an important research field. In this study we explore the possibility of utilizing a commercially available high conductivity grade solution of PEDOT:PSS and further enhance its characteristics by addition of gold nano particles and a MEMS structure to enhance the photo absorption of the OPD by increased surface area. The reported results show comparable sheet resistance values (18.2 Ω/sq for the fabricated electrode) and optical characteristics to the ITO electrode and a much better surface morphology characteristics for the new fabricated electrode.