Soldering of solution-processed organic vertical transistor and light-emitting diode on separate glass substrates by tin micro-balls

The vertical organic space-charge-limited transistor made of P3HT and small-molecule phosphorescent organic light-emitting diode (OLED) are made on two separate glass substrate by blade coating, then soldered vertically together by tin balls with 40 μm diameter. The soldering is done by hot wind of 150 C for 5 min Contact resistance is only 10 Ω. The vertical transistor is annealed at 150 C for 5 min before soldering to enhance the output current up to 25 mA/cm² and give high thermal stability. Both OLED and the annealed vertical transistor are not affected by the soldering process. The vertical transistor has 1/4 of the OLED area and turns on the bottom-emission white OLED up to 300 cd/m² and orange OLED up to 600 cd/m ². The entire operation is within 8 V. OLED and transistor array can therefore be made on separate glass substrates then soldered together to form the display.