Cross-Conjugated Polymer Semiconductors

Cross-conjugated polymer semiconductors represent an unconventional yet promising class of materials with distinct structural and electronic characteristics compared to their linear conjugated counterparts. These systems introduce branched π-electron delocalization, enabling unique optical, electronic, and redox behaviors not accessible through traditional conjugated frameworks. In this review, we provide a comprehensive overview of representative cross-conjugated polymer systems, emphasizing the structure-property relationships and their implications for optoelectronic performance. We highlight recent advances in the design and application of these materials in organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), sensors, electrochromic devices, solar cells, and energy storage. While these polymers typically exhibit lower charge carrier mobilities, several notable examples demonstrate that high mobility can be achieved via structural transformation into linearly conjugated systems through electrical, chemical, or tautomerization mechanisms. Overall, cross-conjugated polymers offer significant potential in emerging applications that demand multifunctionality, environmental responsiveness, and tunable redox behavior.