The Photocharging Effect and Part Electronic Structure Changes of Organic Semiconductors in Photoelectrochemical Water Splitting

In recent years, organic semiconductors have been widely developed to improve the power conversion efficiencies (PCEs) of organic solar cells (OSCs) and organic photoelectrochemical (PEC) devices. Although the PCEs of organic devices is relatively high, the stability and changes of electronic properties of organic semiconductors in long time working are still lack of intensive study. PEC devices are soaked in electrolyte which can diffuse into the devices via the hydrophilia buffer layer (PEDOT: PSS for example) or through the fractures in protection layer caused by the mechanical stresses. The synergistic effects of electrolyte with illumination and aggregation of photo-generated electrons on organic semiconductors are special and still not well established. Herein, the stability and electronic properties changes of organic light absorption layer was directly evaluated after long-term operation in electrolyte under different illumination and bias (controlling the photo-induced electrons aggregation). The photocharging effect of organic bulk heterojunction (BHJ) was observed and the influence factors were studied through electrochemical measurements. The variations of electrical characters of organic light absorption layer such as R-S, C-SC, R-T, C-SS, R-CT after long-term operations were investigated and the corresponding influence factors were speculated from electrochemical impedance spectroscopy (EIS). That will give us a deeper understand of the degradation mechanisms of organic semiconductors in electrolyte and an inspiration for the future stability research of fullerene or popular non-fullerene semiconductors. [GRAPHICS]