Research on liquid metals has been steadily garnering more interest in recent times, especially in flexible electronics applications because of their properties like possesing high conductivity and being liquid state at room temperature.

Highly deformable batteries that are flexible and stretchable are important for the next-generation wearable devices. Several studies have focused on the stable operation and life span of batteries. On the other hand, there has been less focus on the packaging of highly deformable batteries. In wearable devices, solid-state or pouch lithium-ion batteries (LIBs) packaged in aluminum (Al)-laminated films, which protect against moisture and gas permeation, are used. Stretchable elastomer materials are used as the packaging films of highly deformable batteries; however, they are extremely permeable to gas and moisture. Therefore, a packaging film that provides high deformability along with gas and moisture barrier functionalities is required for the stable operation of highly deformable batteries used in ambient conditions. In this study, a stretchable packaging film with high gas barrier functionality is developed successfully by coating a thin layer of liquid metal onto a gold (Au)-deposited thermoplastic polyurethane film using the layer-by-layer method. The film exhibits excellent oxygen gas impermeability under mechanical strain and extremely low moisture permeability. It shows high impermeability along with high mechanical robustness. Using the proposed stretchable gas barrier film, a highly deformable LIB is assembled, which offers reliable operation in air. The operation of the highly deformable battery is analyzed by powering LEDs under mechanical deformations in ambient conditions. The proposed stretchable packaging film can potentially be used for the development of packaging films in advanced wearable electronic devices.

Polymer thin‐film sensors have attracted considerable attention in various applications owing to their highly transparent, flexible, and gas‐permeable features. However, conventional thin‐film sensors based on nanomaterials suffer from poor selectivity in sensing targets and scalability of functions. Therefore, a new approach is required for achieving higher selectivity with simple processibility. This study proposes highly transparent, ultra‐flexible, and gas‐permeable polymer thin‐film sensors using ion gels as the sensing material; the sensors demonstrated the capacity for selective detections. Particularly, this study demonstrates simultaneous and independent sensing of temperature and humidity as a proof of concept. The sensors are fabricated using a simple spray coating method on a thin silicone rubber film (≈25 µm thickness). Owing to their thin‐film shape, the sensors exhibit more than 80% visible light transmittance and a higher gas permeability than the human transepidermal water loss. The temperature and humidity are simultaneously detected with a high sensitivity of 15.4% °C–1 and 2.0% per percentage of the relative humidity, respectively, using gels containing two different ionic liquids (ILs). The results suggest that the easily modifiable nature of ILs enables the fabrication of ultra‐flexible and transparent sensors that can detect various objects using a simple method.

In this study, we have examined the correlation between work function (WF) of indium-tin-oxide (ITO) and open-circuit voltage (V oc ) of heterojunction photovoltaic (PV) cells based on different donor materials. Device configurations of ITO(modified)/SubPc/ C60/BCP/Al and ITO(modified)/ZnPc/C60/BCP/Al were used in this study. Surface modification of ITO electrode through psubstituted benzenesulfonyl chlorides with different electron withdrawing terminal groups (C 6 H 5 -, Cl-and NO 2 -) has exploited to change the WF of ITO up to 5.28 eV with NO 2 -.Chemically modified ITOs and SubPc, ZnPc were used as anode electrode and donor materials, respectively. In order to find the correlation of V oc , two different donor materials with different HOMO levels were used in PV cells. When the SubPc was used as a donor in PV cells, the V oc was strongly dependent on WF of ITO. However, for ZnPc, the V oc was almost independent on WF of ITO due to its low HOMO level and formed ohmic contact at the interface between chemically modified ITO electrodes and ZnPc.