Flexibility of Room-Temperature-Synthesized Amorphous CdO-In₂O₃ Alloy Films and Their Application as Transparent Conductors in Solar Cells

Abstract

Due to their low-temperature deposition, high mobility (>10 cm2/V·s), and electrical conductivity, amorphous ionic oxide semiconductors (AIOSs) have received much attention for their applications in flexible and/or organic electro-optical devices. Here, we report on a study of the flexibility of CdO-In2O3 alloy thin films, deposited on a polyethylene terephthalate (PET) substrate by radio frequency magnetron sputtering at room temperature. Cd1–x In x O1+δ alloys with the composition of x > 0.6 are amorphous, exhibiting a high electron mobility of 40–50 cm2/V·s, a low resistivity of ∼3 × 10–4 Ω·cm, and high transmittance over a wide spectral window of 350 to >1600 nm. The flexibility of both crystalline and amorphous Cd1–x In x O1+δ films on the PET substrate was investigated by measuring their electrical resistivity after both compressive and tensile bending with a range of bending radii and repeated bending cycles. Under both compressive and tensile bending with R b = 16.5 mm, no significant degradation was observed for both the crystalline and amorphous films up to 300 bending cycles. For a smaller bending radius, the amorphous film shows much less electrical degradation than the crystalline films under compressive bending due to less film delamination at the bending sites. On the other hand, for a small bending radius (<16 mm), both crystalline and amorphous films degrade after repeated tensile bending, most likely due to the development of microcracks in the films. To demonstrate the application of amorphous Cd1–x In x O1+δ alloy in photovoltaics, we fabricated perovskite and bulk-heterojunction organic solar cells (OSCs) on glass and flexible PET utilizing amorphous Cd1–x In x O1+δ layers as transparent electrodes. The organic–inorganic hybrid perovskite solar cells (PSCs) exhibit a power conversion efficiency (PCE) of ∼11 to 12% under both front and back illumination, demonstrating good bifacial performance with bifaciality factor >90%. The OSCs fabricated on an amorphous Cd1–x In x O1+δ-coated flexible PET substrate achieve a promising PCE of 12.06%. Our results strongly suggest the technological potentials of amorphous Cd1–x In x O1+δ as a reliable and effective transparent conducting material for flexible and organic optoelectronic devices.

The impact of laser energy on the photoresponsive characteristics of CdO/Si visible light photodetector

“…Additionally, CdO deposited on porous silicon demonstrates an outstanding optical and electrical performance [18]. CdO has been widely applied in broad-based optoelectronic applications such as sensors, transparent electrodes, photo transistors, and solar cells [19][20][21][22].…”

Optimization of solution-processed amorphous cadmium gallium oxide for high-performance thin-film transistors

“…Moreover, in military or aerospace applications where performance is the top priority, the use of cadmium compounds in optoelectronic devices is worth considering. 34,35 There are limited studies exploring the electronic applications of CdO as TCOs, [36][37][38][39][40] photodiodes, 41 and gas sensors, 42 and the application of CdO in TFTs has not been thoroughly investigated. In 2018, Liang et al studied the potential of Ga-Cd-O-based TFTs for photodetector applications.…”

“…There are limited studies exploring the electronic applications of CdO as TCOs, 36–40 photodiodes, 41 and gas sensors, 42 and the application of CdO in TFTs has not been thoroughly investigated. In 2018, Liang et al studied the potential of Ga–Cd–O-based TFTs for photodetector applications.…”