Double-side operable perovskite photodetector using Cu/Cu2O as a hole transport layer.

In this study, a perovskite is integrated with an ultra-thin Cu/Cu2O (CCO) composite film, a transparent material with high mobility, to achieve a double-side and low-voltage operable photodetector. Compared to photodetectors that utilize metal electrode with perovskite, the use of CCO significantly enhances the photocurrent (from nA up to mA). It acts as a large-scale hole transport layer. The photodetector exhibits high responsivities of 6.79 AW-1 [illuminated via the fluorine-doped tin oxide (FTO) side] and 10.23 AW-1 (illuminated via CCO side). The detectivities obtained at both illuminated sides are as high as over 1011 Jones. Additionally, the Cu/Cu2O-covered perovskite effectively prevents the reaction of perovskite in the interface. This work reveals that the perovskite/CCO heterojunction photodetector can be considered a promising candidate for applications in bifacial-illuminated and flexible/wearable optoelectronic technologies.

Adsorption and reactions of propenoic acid and 2-fluoropropanoic acid on Cu(100) and O/Cu(100).

X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, and temperature-programmed reaction/desorption have been employed to investigate the adsorption and reaction pathways of CH2=CHCOOH and CH3CHFCOOH on Cu(100) and oxygen-precovered Cu(100) [O/Cu(100)]. In the case of CH2=CHCOOH on O/Cu(100), CH2=CHCOO is the surface intermediate detected between 110 K and 400 K. CH2=CHCOO is adsorbed vertically and can change adsorption sites at a higher temperature. The propenoate (acrylate) decomposes at higher temperatures (>500 K), with formation of >C=C=O (ketenylidene) surface species and gaseous products. On Cu(100), CH2=CHCOOH is adsorbed in dimer form and can dissociate to generate CH2=CHCOO and CH3CHCOO intermediates on the surface. The CH3CHCOO continuously recombines with the H from deprotonation of CH2=CHCOOH, resulting in the formation CH3CH2COO. The co-existing CH2=CHCOO and CH3CH2COO further decompose at ∼550 K to evolve reaction products, but without >C=C=O being detected. On O/Cu(100), CH3CHFCOOH readily deprotonates to form CH3CHFCOO at 120 K. This intermediate reacts on the surface at ∼460 K to evolve gaseous products, also producing CH2=CHCOO. In the case of Cu(100), deprotonation of CH3CHFCOOH occurs at ∼250 K, forming CH3CHFCOO. Without oxygen on the surface, this intermediate decomposes into HF and CH2=CHCOO at ∼455 K.

Cu/Cu2O nanocomposite films as a p-type modified layer for efficient perovskite solar cells.

Cu/Cu2O films grown by ion beam sputtering were used as p-type modified layers to improve the efficiency and stability of perovskite solar cells (PSCs) with an n-i-p heterojunction structure. The ratio of Cu to Cu2O in the films can be tuned by the oxygen flow ratio (O2/(O2 + Ar)) during the sputtering of copper. Auger electron spectroscopy was performed to determine the elemental composition and chemical state of Cu in the films. Ultraviolet photoelectron spectroscopy and photoluminescence spectroscopy revealed that the valence band maximum of the p-type Cu/Cu2O matches well with the perovskite. The Cu/Cu2O film not only acts as a p-type modified layer but also plays the role of an electron blocking buffer layer. By introducing the p-type Cu/Cu2O films between the low-mobility hole transport material, spiro-OMeTAD, and the Ag electrode in the PSCs, the device durability and power conversion efficiency (PCE) were effectively improved as compared to the reference devices without the Cu/Cu2O interlayer. The enhanced PCE is mainly attributed to the high hole mobility of the p-type Cu/Cu2O film. Additionally, the Cu/Cu2O film serves as a protective layer against the penetration of humidity and Ag into the perovskite active layer.