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 × 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.