In situ growth of high quality crystals for organic electronics

We envisaged that rapid thermal processing (RTP) widely used in semiconductor device fabrication can be employed for fabricating organic crystalline devices since heating and mass transfer are localized within a small area in RTP. This may result in crystal growth at the location relevant to organic device fabrication in situ, for which RTP has not been used so far. We utilized the RTP technique for the growth of high quality organic crystals from thin films of copper phthalocyanine (CuPc) and rubrene. The crystals were grown in situ on silicon surfaces, which were directly used for device fabrication (organic field effect transistors, OFETs, and organic phototransistors, OPTs). For CuPc devices, the mobility was 0.12 ± 0.11 cm2 V–1 s–1, on/off ratio of up to 106, and photo/dark current ratio of P > 105 (for OPT devices). The mobility of rubrene-based OFETs was 0.31 ± 0.15 cm2 V–1 s–1, on/off ratio of up to 105, and photo/dark current ratio of P ≈ 105. The mobilities are similar to those of previously reported single-crystalline CuPc and rubrene OFETs fabricated on untreated surfaces, and the photoresponses are stronger than those of the reported CuPc and rubrene OPTs. RTP is a general and efficient method to grow high quality organic crystals in situ, significantly advancing fabrication methodology for organic electronic and optoelectronic devices.