Toward Improved Device Efficiency and Stability of Organic Light‐Emitting Diodes via External Pressure Treatment

Herein, the effect of applied external pressure on the electroluminescence characteristics of organic light-emitting diodes (OLEDs) is investigated. It is demonstrated that the proper pressure intensity can improve the carrier mobility of organic transport materials and enhance the photoluminescence (PL) intensity. Indeed, the OLED device efficiency is significantly enhanced by applying the pressure of 0.75 MPa for 10 min, achieving >12% increase in current efficiency. Most interestingly, when 0.75 MPa pressure is applied to the specific organic layer instead of the whole device for 10 min, the green fluorescent OLED shows a 20.1% higher current efficiency than that of the reference device. The authors attribute this pressure effect to the closer contact between the organic functional layers and the decreased molecule distance, thereby facilitating more efficient charge transport in OLED device. Furthermore, highly stable OLEDs with long operation lifetime are achieved by specific pressure condition, indicating positive effects of pressure treatment on device stability.