High performance non-fullerene organic photovoltaics under implant light illumination region

Implantable biomedical electronics, such as pacemakers, drug pumps, cochlear implants, cardioverter-defibrillators, and neurological stimulators, help humans to overcome various diseases. Currently, the power supply for these devices relies on small-size batteries, and replacement of the battery is required after running for a period of time. Recharging the battery could be a way to prolong the replacement cycle. Organic photovoltaics (OPVs) are a class of emerging photovoltaics, which are now becoming more practical with recently developed device and material engineering. The absorption of OPVs using a non-fullerene acceptor (NFA) could be extended to the near-infrared (NIR) region to cover the transmission window of human skin between 650 and 1000 nm. Motivated by this, we conducted a study of NFA-based OPVs under light irradiation of wavelengths of 650–1000 nm for implants. The devices using donor (PTB7-Th) and NFA (IEICO-4F) as the active material have strong absorption in the NIR region and obtained a promising power conversion efficiency (PCE) of 14.3% under the implant light illumination, compared to 8.11% when using a benchmark fullerene derivative-based acceptor (PC71BM). Importantly, the PCE and power density of the NFA-based OPVs are significantly higher than the previously reported fullerene-based OPVs devices. This study shows that NFA-based OPVs have high potential for future applications in powering implants, e.g., through charging batteries.