Organic-based optoelectronics have the potential to provide an energy-efficient way to operate low-power indoor devices and wireless IoT sensors. Organic photovoltaic cells (OPVs) and organic photodetectors (OPDs) show exceptional promise for powering indoor electronic devices sustainably. However, the manufacturing processes for stand-alone OPVs and OPDs can be complex and costly, resulting in high production costs and limited scalability. OPVs can absorb energy and generate electricity, even under very low light conditions, while OPDs are able to acquire images. So far, the independent development paths for OPVs and OPDs have kept them from achieving the level of efficiency necessary for practical use in next-generation, miniaturized devices. An organic-based optoelectronic device from researchers at the Korea Institute of Science and Technology (KIST) integrates OPV and OPD functionality in a high-performance, self-powered, multifunctional device that takes advantage of the synergy between OPVs and OPDs. Organic photovoltaic (OPV) and organic photodetector (OPD) devices efficiently use ambient, unused, and low light to generate electricity and detect light to capture images. OPVs can be used to harvest indoor energy, while OPDs are like cameras that can use indoor light for imaging. Courtesy of Korea Institute of Science and Technology (KIST). The device enables simultaneous energy harvesting and sensing. Moreover, it is the first such device to achieve single-pixel imaging with an organic-based photoelectric photodetector. The device’s single-pixel image sensor captures ambient light, transforms it into electrical energy, and uses the energy to acquire images. In contrast to optoelectronic devices that require specialized cameras in low or standard lighting conditions, the device from KIST can visualize images in low-light conditions, which could improve energy efficiency in indoor environments. The device provides sufficient resolution to discern shapes and movements of objects and can function as a conventional camera or as an element placed on windows or walls. “While primarily functioning as an energy harvester, it can also be applied to detect movement and recognize motion patterns in environments without light,” said researcher Min-Chul Park. To improve performance, the researchers converted the organic semiconductor layer of the device into a multicomponent structure. In indoor environments, the device demonstrated a photoelectric conversion efficiency >32% and a linear dynamic range >130 dB in photovoltaic mode, with no external bias. The researchers determined the free-charge generation yield of the device by quantifying charge carrier dynamics. The device exhibited a high output power density of >81 and 76 µW/cm2 for rigid and flexible OPVs under indoor conditions. The single-pixel image sensor leverages the device’s excellent OPD performance, and according to the researchers, is a feasible prototype for operation in indoor commercial settings. The contrast ratio of the organic-based device, especially in low-light conditions, allows for a much clearer image than conventional silicon devices, which typically offer a linear dynamic range of 100 dB. Additionally, organic-based optoelectronics, such as the KIST device, tend to be more flexible and lightweight than silicon-based devices. The new device could provide a path to further exploration of practical, multifunctional solutions for using IoT indoors. “This holds great promise not only for human-computer interaction research, but also in various industrial sectors, including smart indoor environments,” Park said. The research was published in Advanced Materials (www.doi.org/10.1002/adma.202307523).
