Chlorine-Infused Wide-Band Gap p-CuSCN/n-GaN Heterojunction Ultraviolet-Light Photodetectors

Abstract

Copper thiocyanate (CuSCN) is a p-type semiconductor that exhibits hole-transport and wide-band gap (∼3.9 eV) characteristics. However, the conductivity of CuSCN is not sufficiently high, which limits its potential application in optoelectronic devices. Herein, CuSCN thin films were exposed to chlorine using a dry etching system to enhance their electrical properties, yielding a maximum hole concentration of 3 × 10 18 cm –3 . The p-type CuSCN layer was then deposited onto an n-type gallium nitride (GaN) layer to form a prototypical ultraviolet-based photodetector. X-ray photoelectron spectroscopy further demonstrated the interface electronic structures of the heterojunction, confirming a favorable alignment for holes and electrons transport. The ensuing p-CuSCN/n-GaN heterojunction photodetector exhibited a turn-on voltage of 2.3 V, a responsivity of 1.35 A/W at −1 V, and an external quantum efficiency of 5.14 × 10 2 % under illumination with ultraviolet light (peak wavelength of 330 nm). The work opens a new pathway for making a plethora of hybrid optoelectronic devices of inorganic and organic nature by using p-type CuSCN as the hole injection layer.

Cl2-Doped CuSCN Hole Transport Layer for Organic and Perovskite Solar Cells with Improved Stability

“…In this work, we exposed CuSCN thin films to Cl 2 gas using a dry etching system with controllable background pressure and Cl 2 concentration. 19 As a result, we obtained Cl 2 −CuSCN films with significantly increased conductivities. We then studied the effect of Cl 2 treatment has on the device performance of CuSCN-based OSCs and inverted PSCs.…”

“…Its high optical transparency suppresses any parasitic absorption of the light generated from the active layer. − In organic and perovskite solar cells (OSCs and PSCs), the CuSCN layer allows the extraction of holes from the photoactive layer, again suppressing any parasitic absorption and allowing the incident radiation of all wavelengths to reach the photoactive layer. − Theoretical studies have linked the advantages of CuSCN as an HTL to its usual lack of any deep carrier trap states and its minimal valence band offset with the archetypal perovskite CH 3 NH 3 PbI 3 . In ultraviolet-based photodetectors (UVPDs), the wide bandgap of CuSCN allows unhindered high absorption in the UV region and could form not only metal–semiconductor–metal (MSM) UVPDs but also p-n junction UVPDs when combined with n -type material. − Finally, CuSCN is one of the few materials for p -channel thin film transistor (TFT) fabrication due to its hole transport selectivity. − …”

“…In this work, we exposed CuSCN thin films to Cl 2 gas using a dry etching system with controllable background pressure and Cl 2 concentration . As a result, we obtained Cl 2 –CuSCN films with significantly increased conductivities.…”

Direct, simple, rapid, and real‐time monitoring of ultraviolet B level in sunlight using a self‐powered and flexible photodetector

“…Nevertheless, the similarity in the UVA photoresponse can be observed as mentioned above (at a constant UVA‐induced photocurrent under UVA intensity higher than a certain threshold) because the energy gap for electron transport from TFB to PEDOT:PSS (0.55–1.02 eV) is always smaller than that for electron transport from TFB to ZnS (1.95 eV, Figure S5b). Additionally, it is expected that the selectivity of ZnS‐based UVB‐C photodetector in the same structure as device B could be improved by replacing TFB with wider‐bandgap hole transport layers such as NiO (3.5 eV) and CuSCN (3.9 eV) 47–48 …”

Fast Response Self-Powered UV–Vis–NIR Broadband Photodetector Based on a Type II Heterojunction of AgIn5Se8/FePSe3

“…Furthermore, a conventional photodetector requires an external power supply, which induces the circuit complexity of designing the devices and limits their application in special environments and situations. , Therefore, it is particularly important for fabricating self-powered high-performance photodetectors as they do not require an external voltage when operating and thus reduce energy consumption. In general, self-powered photodetectors can be achieved by constructing p–n junctions, − Schottky junctions, − and heterojunctions. − Photogenerated electrons and holes are rapidly separated at the heterostructure interface through the built-in electric field, realizing the self-powered and rapid response of the photodetector.…”