Bi₂S₃‐Cu₃BiS₃ Mixed Phase Interlayer for High‐Performance Cu₃BiS₃‐Photocathode for 2.33% Unassisted Solar Water Splitting Efficiency

Abstract

To realize practical solar hydrogen production, a low‐cost photocathode with high photocurrent density and onset potential should be developed. Herein, an efficient and stable overall photoelectrochemical tandem cell is developed with a Cu3BiS3‐based photocathode. By exploiting the crystallographic similarities between Bi2S3 and Cu3BiS3, a one‐step solution process with two sulfur sources is used to prepare the Bi2S3–Cu3BiS3 blended interlayer. The elongated Bi2S3‐Cu3BiS3 mixed‐phase 1D nanorods atop a planar Cu3BiS3 film enable a high photocurrent density of 7.8 mA cm−2 at 0 V versus the reversible hydrogen electrode, with an onset potential of 0.9 VRHE. The increased performance over the single‐phase Cu3BiS3 thin‐film photocathode is attributed to the enhanced light scattering and charge collection through the unique 1D nanostructure, improved electrical conductivity, and better band alignment with the n‐type CdS layer. A solar‐to‐hydrogen efficiency of 2.33% is achieved under unassisted conditions with a state‐of‐the‐art Mo:BiVO4 photoanode, with excellent stability exceeding 21 h.

High-efficiency unbiased water splitting with photoanodes harnessing polycarbazole hole transport layers

“…Moreover, it is noteworthy that both types recorded the highest STH conversion efficiency among the mode T tandem devices, which require systematic engineering for the separation of the absorption wavelength (Tables S4 and S5 (ESI†)). 40–59 These results emerge from the high-efficiency tandem device-tailored photoanode, in which a remarkable HTL, CPF-TCB, simultaneously increases the photocurrent and photovoltage of Mo:BiVO 4 .…”

Prospects of copper–bismuth chalcogenide absorbers for photovoltaics and photoelectrocatalysis

“…A recent study reported a low carrier lifetime of 0.7 ns, indicating high recombination losses. 20 This clearly suggests the active role of deep defects in the material.…”

“…The presence of mixed phases can result in structural instability, which can lead to a loss in the photocatalytic activity and overall performance. However, recently, in a report by Moon et al , 20 it was shown that mixed phases can actually allow better band alignment with the n-type layer (band diagram showing the relative energy positions of each of the semiconductors is shown in Fig. 10j).…”

“…17,18 Alternatively, the impressive solar-to-hydrogen (STH) conversion efficiency of 2.04% has been reported for a CBS photocathode-based PEC device, demonstrating excellent prospects for photoelectrocatalysis. 19 Recently, Moon et al 20 achieved a solar-to-hydrogen efficiency of 2.33% under unassisted conditions using a Bi 2 S 3 –Cu 3 BiS 3 mixed phase interlayer. The results displayed a high onset potential of 0.9 V ( vs. RHE) and three-times higher photocurrent density (7.8 mA cm −2 , at 0 V vs. RHE) compared to the single-phase Cu 3 BiS 3 -photocathode.…”

Designing idealised devices for bias-free solar water splitting

“…In addition to the photoanodes, narrow-bandgap p-type semiconductors are commonly used as back photocathodes to absorb long-wavelength sunlight. Si, 14,15 Cu(In,Ga)Se 2 (CIGS), 16 Cu 2 ZnSnS 4 (CZTS), 17 Cu 2 O, 18 Sb 2 Se 3 , 19 Cu 3 BiS 3 , 20 and halide perovskites 21 have attracted considerable attention as photocathode materials.…”