Charge-Transfer-Driven Enhanced Performance of CuNi Nanoparticles-Anchored Carbon Nanotube-Based Photodetectors

Achieving broadband photoresponse properties for high-performance photodetectors (PDs) in future optoelectronic systems holds significant interest. Carbon nanotubes (CNTs) have been the subject of extensive study as active materials due to their excellent charge transport properties; however, devices based on pristine CNT often exhibit a low photoresponse, primarily attributed to the loss of light harvesting and charge separation. Anchoring bimetallic surface plasmon resonance (SPR) nanoparticles (NPs) onto CNTs is an effective approach to boost the performance of CNT-based PDs. Here, we report the photodetection performance of CNT/n-silicon (Si) and CuNi (CN) bimetallic NPs-anchored CNT-based hybrid (CN-CNT)/n-Si PDs in the wavelength range of 400–800 nm. Spectroscopic and density functional theory (DFT) investigations reveal a pronounced interfacial charge transfer between the CN NPs and CNTs, resulting in enhanced optical absorption and suppressed charge carrier recombination. The pristine CNT/n-Si PDs exhibit a responsivity (R) of 16 A W−1, specific detectivity (D) of 1.2 × 109 Jones, and an external quantum efficiency (EQE) of 3818% at 520 nm under a reverse bias of −4 V. In comparison, the CN-CNT/n-Si PDs demonstrate a marked improvement in photoresponse, delivering an R of 23.4 A W−1, a D of 3.4 × 109 Jones, and an EQE of 6514% at 460 nm and −4 V bias. Correlative analysis using valence-band X-ray photoelectron spectroscopy, Raman spectroscopy, and DFT calculations attributes this enhancement to charge-transfer-induced modulation of the built-in potential at the CN NPs/CNT junction, which effectively promotes photocarrier separation, suppresses recombination losses, and facilitates efficient transport of photogenerated electron–hole (e–h) pairs.