Organic Photovoltaic Materials for Mechanoluminescence Sensing and Structural Health Monitoring

Structural health monitoring (SHM) is an essential tool for ensuring safety and integrity while detecting the progression of damage within engineering structures to estimate expected failure.1-4 This is usually done over time through periodically sampled response measurements to monitor changes in material and geometrical properties of a given system. Take a commercial aircraft, for example, that usually travels at around 580 MPH. Any impact at this speed could cause damage to the material.  If it goes unnoticed, then it will progress and further risk ultimate failure or the lives of that on-board.5 Because of situations like this, there is a demand for a real-time SHM device within damage-prone systems.  A proposed idea to meet the demand is a flexible mechanoluminescent (ML)-organic photodiode. The device consists of a photodiode constructed on top of an ML layer which emits light when it experiences some mechanical action, such as pressure.

Organic photovoltaic (OPV) materials can be used as a photo-absorbing layer for ML light. This OPV layer is made up of a blend of donor polymer, poly (3-hexylthiophene-2,5-diyl (P3HT), and non-fullerene acceptor (BTP-4F or Y6). The broad ultraviolet-visible to near-infrared light absorption and excellent charge transport efficiency make P3HT:Y6 active materials a promising alternative as the light absorbing layer to detect photon emission from the ML layer in flexible organic photodiodes for sensing and SHM. The pressure sensor is a vertical device structure of indium tin oxide (ITO)/tin oxide (SnO2)/P3HT:Y6/silver (Ag) electrode. The current-voltage measurements revealed that the P3HT:Y6 OPVs exhibited an excellent rectification ratio.  When this technology is coupled with a software and data acquisition system, sensor’s data can be received and interpreted

• Advantages:
• The response time measurement demonstrated that the device has an impressive response speed. The three-point bending test unveiled that the pressure sensor possesses excellent stability after several cycles.