Utilizing a Siloxane-Modified Organic Semiconductor for Photoelectrochemical Water Splitting

Abstract

We explore the potential of employing diketopyrrolopyrrole (DPP) based π-conjugated OSs as a hole transport layer material in heteroatom-doped hematite (Ti–Fe2O3/Ge–Fe2O3) photoanodes for efficient photoelectrochemical water splitting. The siloxane-modified π-conjugated polymer (PSi) with a high carrier mobility and crystallinity revealed great potential to extract holes by forming a built-in potential with hematite photoanodes while showing high stability in an alkaline electrolyte for photoelectrochemical water oxidation. Because of the easy hole extraction and subsequent fast hole transport property of the PSi interlayer between NiFe(OH)x and Ge-doped porous Fe2O3(Ge-PH), NiFe(OH)x/PSi/Ge-PH showed a 1.8-fold increase in photocurrent density (4.57 mA cm–2 at 1.23 VRHE) with a cathodic shift of the onset potential (0.735 VRHE) and good stability for 65 h compared to Ge-PH. This study demonstrates the successful use of inherently unstable π-conjugated OSs as a hole extracting/transport medium in a photoanode, addressing the intrinsic recombination issues of hematite for efficient and stable water splitting.