Cu-Doped NiO_x as an Effective Hole-Selective Layer for a High-Performance Sb₂Se₃ Photocathode for Photoelectrochemical Water Splitting

Abstract

Although antimony triselenide (Sb2Se3) has been intensively investigated as a low-cost p-type semiconductor for photoelectrochemical (PEC) water splitting, most previous studies focused on only the top interface of Sb2Se3 photocathodes. Herein, a solution-processed Cu-doped NiO x (Cu:NiO x ) thin film is proposed as an effective bottom contact layer for the Sb2Se3 photocathode. The photocurrent density of the Sb2Se3 photocathode is improved to a record-high level of 17.5 mA cm–2 upon the insertion of Cu:NiO x capable of blocking the recombination at the back interface, while facilitating hole extraction. Electrochemical impedance spectroscopy and intensity-modulated photocurrent spectroscopy, in conjunction with other observations, indicate that the enhanced photocurrent is due to the improved quality of the bottom contact without a noticeable change in the top interface. This study not only provides new insight into the role of the bottom contact layer in photocathodes, but also is an important step toward efficient PEC H2 production via a solution-processable Earth-abundant photoelectrode.

Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting

“…successive depositions at 340 and 460°C followed by cooling the chamber naturally after deposition). The role of the Au layer in Sb 2 Se 3 photoelectrodes, which facilitates the transfer of photo-generated holes, has been discussed in previous reports on Sb 2 Se 3 for PEC water splitting 26,32 and thin-film solar cells 33 . Despite the filmtype morphology, there were some pin-holes resulting in exposure of the substrate (red circles in Fig.…”

“…It has also been reported that Sb 2 Se 3 is intrinsically stable towards photocorrosion in strong acidic media unlike Cu 2 O, which is vulnerable to photocorroson 22 . Owing to these merits, the photocurrent density of the Sb 2 Se 3 photocathode has improved rapidly from the initially reported value of 2.5 mA cm −2 to 17.5 cm −2 at 0 V against the reversible hydrogen electrode (RHE) over the short period of its development [23][24][25][26] . However, it is still far below the theoretical maximum (about 40 mA cm −2 , assuming a 1.2 eV E g and a 100% incident photon-to-current efficiency (IPCE)).…”

Stable and tunable phosphonic acid dipole layer for band edge engineering of photoelectrochemical and photovoltaic heterojunction devices

“…6B) with onsets comparable to the very best reports in the literature. [49][50][51] Furthermore, the large dark current observed in the Sb 2 Se 3 /TiO 2 device is suppressed when a dipole layer is utilized (Fig. 6A, dotted lines).…”

Scalable Core–Shell MoS2/Sb2Se3 Nanorod Array Photocathodes for Enhanced Photoelectrochemical Water Splitting

“…In a strongly acidic electrolyte (1 m H 2 SO 4 , pH ≈ 1), Sb 2 Se 3 thin film prepared with the selenization of electrodeposited Sb and Pt cocatalyst further improves the photocurrent density to 16 mA cm −2 at 0 V RHE . By introducing a Cu‐doped NiO x hole‐selective layer as an effective bottom contact layer for a solution‐processed Sb 2 Se 3 photocathode, a record photocurrent density of 17.5 mA cm −2 at 0 V RHE in acidic electrolytes is achieved …”