PTQ10:L8-BO organic photoactive layers enable improved stability for solar water oxidation and enhanced unassisted water splitting

Dabóczi, Mátyás and Al Lawati, Noof and Stewart, Katherine and Zhi, Maoqing and Müller, Jolanda Simone and Kim, Ji-Seon and Nelson, Jenny and Eisner, Flurin and Eslava, Salvador (2026) PTQ10:L8-BO organic photoactive layers enable improved stability for solar water oxidation and enhanced unassisted water splitting. EES Solar. ISSN 3033-4063

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Abstract

Integrating organic photovoltaics into anodes (IPV-anodes) represents a promising way to exploit the excellent optoelectronic properties of organic polymer: non-fullerene bulk-heterojunctions (BHJ) for solar-to-fuel applications. However, the high voltage losses, poor photochemical stability and high synthetic complexity of the most commonly used polymer: non-fullerene combinations have limited their full potential. Here, we address these limitations by introducing a BHJ comprising the lowsynthetic-complexity polymer PTQ10 and the near-infrared absorbing acceptor L8-BO. By integrating this new BHJ with a graphite sheet functionalised with a NiFeOOH catalyst, we achieve a low onset potential of +0.64 VRHE, a photocurrent density of 21 mA cm−2 at +1.23 VRHE and a t80 operational stability of 22 h under full AM1.5 G illumination (i.e., without using any UV filter) for water oxidation. These values represent a 40 mV increase in photovoltage and a sevenfold improvement in operational stability (t80 extended from 3 h to 22 h) compared to reference IPV-anodes based on the ternary D18:PM6:L8-BO photoactive blend. Spectroscopic analyses reveal that these improvements stem from the reduced non-radiative voltage losses (from 0.24 V to 0.19 V) and superior photochemical and morphological stability of the PTQ10:L8-BO blend compared to the reference blend. Building on these advances, we demonstrate monolithic tandem IPV-anodes integrating PTQ10:IDIC and PTQ10:L8-BO organic blends to achieve a solar-to-hydrogen efficiency of 6.2%, offering critical insights for boosting the stability and efficiency of integrated solar-to-hydrogen systems working without any external bias.

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