High-performance ambipolar organic phototransistors based on core−shell p−n junction organic single crystals

Abstract

Electronic devices based on organic single-crystal semiconductors have been used in a range of applications, suggesting their possible use as core components of high-performance electronic devices. Various electronic devices based on unipolar organic semiconducting crystals have high electrical and optoelectronic properties compared to thin-film-based devices due to the intrinsic nature of the single crystal, such as a long-range order and a high degree of structural perfection. However, only a few studies have examined electronic devices using organic single crystals with ambipolar characteristics. This study investigated the electrical and optoelectronic characteristics of a core−shell organic semiconducting crystal composed of an n-type single-crystal nanowire as the core and p-type single crystal as the shell. The device showed ambipolar behavior with balanced electron and hole mobilities (maximum electron and hole mobility of the core−shell ambipolar crystal; 1.41 × 10−1 and 8.31 × 10−2 cm2 V−1 s−1, respectively). A core−shell ambipolar crystal was also used as the photoactive layer of a complementary metal−oxide−semiconductor (CMOS)-like inverter, and sharp voltage conversion was observed near 50 V at a supply voltage of 100 V with a gain of 23.7. Furthermore, phototransistors based on core−shell organic crystals had excellent optoelectronic characteristics with remarkable performance; the estimated photoresponsivity (R), photocurrent/dark-current ratio (P), external quantum ratio (EQE, η), and detectivity (D*) were 4.91 × 104 A W−1, 2.14 × 102, 1.23 × 107%, and 1.03 × 1015 Jones, respectively. Phototransistors based on core−shell semiconducting crystals also showed rapid photoswitching behaviors under pulsed incident light. The ambipolar core−shell crystals we developed can potentially be used for various applications, including high-performance integrated circuits and photosensing electronic devices.