ABSTRACT Understanding the energetic disorder in polymeric organic semiconductors is critical for optimizing their charge transport properties in photoconductive and optoelectronic devices. In this study, we systematically investigated the influence of molecular weight on the density of states (DOS) and photorefractive (PR) performance of poly(N‐vinylcarbazole) (PVCz)‐based composites. Photoelectron yield spectroscopy (PYS) revealed that the energetic disorder, characterized by the deviation of the DOS ( σ DOS ), decreases with increasing PVCz molecular weight, despite the HOMO energy level remaining constant. Photorefractive performances showed that diffraction efficiency increases and response time decreases with increasing molecular weight, exhibiting a strong correlation with σ DOS . Thermal and structural characterizations—including glass transition temperature ( T g ), X‐ray diffraction (XRD), density ( ρ ), and fractional free volume (FFV)—demonstrated that σ DOS is most strongly correlated with T g (R 2 = 0.931), suggesting that chain rigidity and packing density are key factors influencing energetic disorder. The Gaussian disorder model (GDM) was applied to estimate carrier mobility, further validating the DOS‐derived transport trends. This work establishes T g as a practical and predictive proxy for σ DOS , offering a simple and effective approach for evaluating energetic disorder in polymeric semiconductors. Our findings provide a framework for the rational design of PR materials and extend to broader applications in organic electronics.
Kinashi et al. (Thu,) studied this question.