In this paper, we show that size controlled nanometer phase structure and nanometer thickness film of blend polymers can be obtained by a physical method under the ultra thin phase separation (UTPS) concept. The blend films of poly 3-(2-(5-chlorobenzotriazolo) ethyl) thiophene (PCBET)/polyvinylcarzole (PVK) system and PCBET/PMPMA (Poly-(p-(methyl)-phenylmethaerylate) system were investigated. Among AFM images of various mixing ratios, the phase separation was clearly observed. The average size of dispersion phase was in the range 100 nm to 1.2 mu m. Here we can obtain not only the mono decentralized micro/nano phases, but also the different size and compact arrangement of the micro/ nano phases of the luminescent polymers. We employ a modified AFM (atomic force microscopy) tip to investigate the electrical properties of UTPS in which there are the mono micro/nano phases of semiconductor polymer in matrix. The lateral force microscopy (LFM) confirmed the results of AFM. Photo-luminescences (PL) in the blend films of PCBET/PVK system and PCBET/PMPMA system were investigated. The results suggest that the suitable blend leads to the enhancement of PL emission of PCBET. (c) 2006 Elsevier B.V. All rights reserved.