Organic light-emitting transistor technology

The organic light-emitting transistor (OLET) is an emerging optoelectronic device having the structure of a thin-film transistor and the capability of light generation [1]. Bright/multicolor OLETs may allow electroluminescent display fabrication with simpler driving circuits. Furthermore, the most advanced OLETs encompass a huge technological potential for the realization of intense nanoscale light sources for a variety of applications, including miniaturized disposable photonic bio-sensing devices and highly integrated optoelectronic systems. In terms of performance and reliability, OLED technology is by far the most developed and active matrix OLED displays have been introduced into the market. However, detrimental device-related processes affecting OLED operation under high injection conditions are the exciton-charge interactions and the photon losses at the electrodes. The proximity (within tens of nanometer) of the contacts to the OLED light generation region induces losses due to absorption of the emitted photons. Moreover, the highly dense electron and hole currents converge to the light emitting layer, where they form but spatially coexist with the excitons, and lead to significant exciton-charge quenching. Indeed, this mechanism is predicted to be greater than any other quenching effects and should be controlled to enhance OLED efficiency, brightness, and stability even further. Thus, at the base of the OLET development there is the possibility to enable new display/light source technologies, and exploit a transport geometry to suppress deleterious photon losses and exciton quenching mechanisms inherent in the OLED architecture. Here, recent advances and future prospects of light-emitting field-effect transistors will be discussed, with particular emphasis on organic semiconductors and the role played by the material properties, device features and the active layer structure in determining the device performances. In particular, we introduce the concept of using a p-channel/emitter/n-channel trilayer semiconducting heterostructure in OLETs, providing a new approach to markedly improve OLET performance. In this architecture, exciton– charge annihilation and electrode photon losses are prevented. Our devices are >100 times more efficient than the equivalent OLED, >2X more efficient than the optimized OLED with the same emitting layer and >10 times more efficient than any other reported OLETs.