Photoluminescent carbon nanotubes are expected to become versatile room-temperature single-photon sources that have applications in quantum information processing. Quantum emission from carbon nanotubes is often induced by localization of excitons or exciton-exciton annihilation. Here, we modify the local energy landscape of excitons by decorating nanoscale pentacene particles onto air-suspended single-walled carbon nanotubes [1]. Directional exciton diffusion from the undecorated region to the decorated site is demonstrated, suggesting exciton trapping induced by local dielectric screening from pentacene particles. Photoluminescence and photon correlation measurements on a representative carbon nanotube reveal enhanced exciton-exciton annihilation and single-photon emission at room temperature. Pentacene particles are shown to promote strong photon antibunching at the decorated site, indicating that noncovalent functionalization using molecules can be an effective approach for energy landscape modification and quantum emission in carbon nanotubes.Work supported in part by MIC (SCOPE 191503001), JSPS (KAKENHI JP20H02558, JP19J00894, JP20J00817, JP20K15121, JP20K15137, JP20K15112 and JP20K15199), and MEXT (Nanotechnology Platform JPMXP09F19UT0079). K.O. and D.Y. are supported by the JSPS Research Fellowship. D.K. is supported by the RIKEN Special Postdoctoral Researcher Program. We acknowledge RIKEN Materials Characterization Team for access to the transmission electron microscope, and RIKEN Advanced Manufacturing Support Team for technical assistance.[1] Z. Li, K. Otsuka, D. Yamashita, D. Kozawa, Y. K. Kato, ACS Photonics 8, 2367 (2021).