High-Performance Ambipolar Organic Phototransistors Based on Core-Shell p-n Junction Organic Single Crystals

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 x 10(-1) and 8.31 x 10(-2) cm(2) 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, eta), and detectivity (D*) were 4.91 x 10(4) A W-1, 2.14 x 10(2), 1.23 x 10(7)%, and 1.03 x 10(15) 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.