Effect of Organic Semiconductor Morphology on the Performance of Photoelectrochemical Cells

Abstract

Photoelectrochemical cells (PEC cells) are attracting significant attention as promising energy conversion devices, capable of transforming solar energy into chemical fuels such as hydrogen. Recently, organic semiconductors have been extensively studied as photoactive layers in PEC cells due to their high absorption coefficients and solution processability, enabling cost-effective production of solar fuels on a large scale. However, organic semiconductor-based PEC cells still face challenges in economic viability due to low efficiency and stability issues. Additionally, there is a lack of research on the correlation between morphology and efficiency/stability. To address this knowledge gap, our study aimed to elucidate this relationship by fabricating and comparing two types of PEC cell structures. The bulk heterojunction (BHJ) structure with uniformly mixed donor and acceptor materials, and a sequentially deposited pseudo-bilayer structure. Interestingly, the pseudo-bilayer (PS-Bi) structure exhibited higher performance than the BHJ structure at low potentials. Electrochemical impedance spectroscopy (EIS) confirmed that this result was due to the ability of PS-Bi to effectively suppress unnecessary charge recombination at low potentials.