Influence of C-60 acceptor layer position on near infrared photosensitive organic field-effect transistors based on tri-layer planar heterojunction

摘要

Performance of near infrared (NIR) photosensitive organic field-effect transistors (PhOFETs) based on NIR sensitive metal phthalocyanines (MPcs) single active layer are generally poor due to its low carrier mobility. NIR PhOFETs based on tri-layer planar heterojunction (PHJ) formed by integrating a high mobility channel layer, a NIR sensitive MPcs donor layer and an acceptor layer was demonstrated an effectively way to realize high photosensitivity. The position of the acceptor layer, i.e. beneath and/or above the source/drain electrodes, seriously affects carrier injection in the device. In order to illustrate the dependence of acceptor layer position on device performance, NIR PhOFETs based on pentacene/SnPc/C-60 tri-layer PHJ with conventional structure and sandwich structure were fabricated and characterized, as well as pentacene/SnPc bi-layer PHJ NIR PhOFETs. For NIR light with a wavelength of 850 nm, tri-layer PHJ NIR PhOFETs in sandwich structure exhibited a high photoresponsivity of 7049 mA/W, which was (similar to)1.89 and 8 times larger than that of PhOFETs based on conventional tri-layer PHJ and bi-layer PHJ, respectively. The enhanced photoresponsivity of the device was attributed to its inherent high mobility, high absorption, high exciton dissociation efficiency and improved carrier injection.