posted on 2021-08-31, 17:15authored byYing Wang, Menglin Li, Baobing Fan, Yeung Sum Wong, Chung
Yan Lo, Cheuk Kai Gary Kwok, Sujit Kumer Shil, Hin-Lap Yip, Alex K.-Y Jen, Sai-Wing Tsang, Kin Man Yu
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–xInxO1+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–xInxO1+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 Rb = 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–xInxO1+δ alloy in photovoltaics,
we fabricated perovskite and bulk-heterojunction organic solar cells
(OSCs) on glass and flexible PET utilizing amorphous Cd1–xInxO1+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–xInxO1+δ-coated
flexible PET substrate achieve a promising PCE of 12.06%. Our results
strongly suggest the technological potentials of amorphous Cd1–xInxO1+δ as a reliable and effective transparent conducting
material for flexible and organic optoelectronic devices.