HIroaki Jinno

Ultrathin perovskite solar cells (PSCs), defined as flexible devices with total thicknesses below 10 μm, are promising candidates for next‐generation space photovoltaics owing to their extremely low weight and high mechanical compliance. Although the radiation tolerance of rigid PSCs has been widely studied, that of flexible—particularly ultrathin—PSCs remains insufficiently explored, mainly due to radiation‐induced staining and degradation of conventional plastic substrates under high‐dose gamma‐ray irradiation. Here, we demonstrate 4 μm‐thick ultrathin flexible PSCs fabricated on radiation‐stable parylene/SU‐8 substrates, exhibiting exceptional gamma‐ray tolerance under severe total ionizing dose (TID) conditions. The parylene/SU‐8 substrate preserves optical transparency and mechanical compliance after irradiation, effectively suppressing substrate‐induced staining artifacts. Consequently, the ultrathin PSCs retain 99% of their initial power conversion efficiency after exposure to 890 krad (Si). By comparison with rigid PSCs, we show that irradiation‐induced short‐circuit current loss and fill‐factor enhancement originate from the PSC stack itself rather than from the substrate, with the current reduction being consistent with phase segregation in the perovskite layer. These results highlight radiation‐stable ultrathin substrates and interface design as key enablers for highly radiation‐tolerant ultrathin PSCs for future space applications.

Abstract Dual‐band organic photodetectors (DB‐OPDs) offer adaptive detection of two distinct wavelengths by switching the voltage, making them promising candidates for wearable bio‐imagers. Although many studies have been conducted on rigid DB‐OPDs to date, flexible DB‐OPD with comparable performance to rigid counterparts has not been reported because of the vulnerability and lower transmittance of flexible substrates and electrodes. In this study, a 5.6‐µm‐thick ultra‐flexible DB‐OPD for visible and near‐infrared (NIR) light selective detection is reported. It shows high mechanical durability with stable electrical characteristics after 500 repetitions of intense bending at a radius of 0.5 mm. Furthermore, high specific detectivities exceeding 10 ¹¹ Jones in both the visible and NIR spectral ranges are achieved by incorporating an efficient donor to enhance the photocurrent and depositing a top electron transport layer to suppress the dark current, while minimizing damage to the underlying NIR‐sensitive layer. To validate the feasibility of the ultra‐flexible DB‐OPD in bio‐imaging, dual‐spectral peripheral oxygen saturation (SpO ₂ ) measurements are performed under a continuous‐spectrum light source covering both the visible and NIR regions. The results highlight the potential of the ultra‐flexible DB‐OPD for wearable oximeter application.