<p>Diketopyrrolopyrrole (DPP) and its derivatives have attracted significant attention in organic electronic devices due to the advantageous features of the DPP core, including strong electron-withdrawing character, high planarity, excellent optoelectronic properties, and thermal stability. Progress in this field has been closely linked to advances in synthetic strategies, particularly chemical modification at the nitrogen position of the DPP core. <i>N</i>-Alkylation represents an effective approach for tuning solubility, molecular packing, optical absorption, and semiconducting behavior. This review focuses on <i>N</i>-alkylated DPP-based small molecules and their applications in organic field-effect transistors (OFETs) and photodetectors. The first part provides a concise historical overview of the DPP core, its key properties, and commonly employed synthetic routes for <i>N</i>-alkyl DPP derivatives. The subsequent part summarizes the device performance of <i>N</i>-alkyl DPPs and their π-expanded derivatives in OFETs and photodetector devices, highlighting structure-property performance relationships. Finally, current challenges and future perspectives are discussed, offering guidance for the rational design of high-performance organic electronic materials. This review will serve as a valuable reference for the researchers working on DPP-based materials and developing high-performance organic electronic devices.</p> Graphical abstract <p></p>