High-Performance Photodetectors Based on Suspended Ultralong Carbon Nanotubes.

Photodetectors are in huge demand in multiple fields, such as remote sensing, chemical detection, security, and medical imaging. Carbon nanotubes (CNTs) are promising candidates for high-performance photodetectors due to their extraordinary optical and electrical properties. However, the performance of previously reported CNT-based photodetectors is far from the intrinsic photoelectrical properties of CNTs because of the noncontinuous lengths, structural defects, and unsatisfactory structural design of the previously used short CNTs. The key to improving the performance of CNT-based photodetectors is to increase the length and structural quality of the CNTs. Herein, high-performance photodetectors were fabricated by using high-density suspended ultralong CNTs (SUCNTs). The suspended structures of ultralong CNTs not only reduced the electron-phonon interactions generated by substrates but also largely avoided bolometric effects through efficient heat dissipation. Moreover, the characteristics of high areal density and defect-free structures of SUCNTs could increase the effective absorption areas and improve their carrier mobility, resulting in enhanced photoconductive responses. Consequently, compared with the nonsuspended short CNTs, the SUCNT-based photodetectors achieved significantly improved photodetection performance, such as high responsivity (0.181 A W), detectivity (1.20 × 10 cm Hz W), ultrafast response (0.13 ms), and broad detection range (405-850 nm).