Process ambient effects on defect state generation in CuI films: Toward multimodal sensor application via patternable CuI arrays

With the advent of CuI as one of promising metal halides, great attention is recently paid to optoelectronic applications. However, CuI formation and its defect states are rarely investigated according to atmospheric conditions exposed to Cu films before iodization. Here, CuI films, prepared for the respective atmospheric conditions (or glove box), are systematically studied via various peak analyses, elucidating that the absorbed oxygen and moisture on Cu film before iodization significantly affect the chemical composition ratio (I/Cu) as 1.06 ± 0.01 (or 0.73 ± 0.05) in the glove box (or atmospheric) ambient. Furthermore, the decrease of electrical conductivity and its improved photodetection properties (PDPs) for CuI devices are consistently demonstrated with the rise of holding time in atmospheric conditions, which is ascribed to the increased iodine vacancy (V_I) in CuI film. Furthermore, for process durability, various solvents and their exposure effects on electro/optical properties, including chemical composition, are investigated for 7 × 7 CuI arrays, denoting that short-term exposure is compatible within 20 %. For the practical validation, multimodal sensors based on flexible CuI thermistors with the average of B and TCR (%) as (3846 ± 427) K and -(4.32 ± 0.47) % and array-based CuI photodetectors are successfully demonstrated, illustrating of the utility of these findings for the envisioned, flexible optoelectronics.