A promising ternary sulfide bidirectional p-n heterojunction for unassisted tandem photoelectrochemical cells.

There has been great demand for high-efficiency, low-cost, and abundant photoelectrode materials for photoelectrochemical (PEC) systems. Here, we studied the PEC performance of ternary sulfide photoelectrodes (ZnIn2S4 and CuInS2) with the same nanostructure and applied bidirectional p-n heterojunctions with energy levels that were well matched to the unassisted tandem PEC cell device. Moreover, ZnIn2S4/CuInS2 and CuInS2/ZnIn2S4 were used as a photoanode and photocathode, respectively, in the unassisted tandem PEC cell device, which achieved a relatively high photocurrent density of 0.06 mA cm-2. This work provides new ideas for the design and manufacture of high-efficiency unassisted tandem PEC cell devices.