P-type -conjugated BTPDS-8 organic molecule for broadband hybrid photodetector with organic/inorganic heterostructure

A novel p -type pi-conjugated organic small molecule 3,7-bis(4-([2,2 ':6 ',2"-terpyridin]- 4 '-yl)phenyl)- 5H- dibenzo[a,d][7]annulen-5-one (named as BTPDS-8) in which terpyridinyl units are linked to the dibenzosuberenone backbone by a phenyl bridge was successfully synthesized in four reaction steps. The synthesized organic material BTPDS-8 was fully characterized using 1H NMR, 13C NMR, IR, and HRMS spectroscopy techniques. Then, eleven BTPDS-8/Si heterojunctions were fabricated having non-linear current -voltage characteristics. Among these devices, the one with the highest rectification ratio (with 8.43 x105) was analyzed in detail under UV and IR light as well as different intensities of visible light. Experimental results showed that the device has good photoresponse performance under any light source in addition to self -driven mode characteristics. It was observed that the saturation current and barrier height increased, and the ideality factor decreased, depending on the light intensity under visible light. Photocurrent, on/off ratio, responsivity, detectivity and NPDR were calculated from the optical measurements. The broad spectrum photoresponse of the BTPDS-8/Si heterojunction from UV to IR demonstrated that the device has the potential to be used as a broadband photodetector. The best performance was obtained under 850 nm IR light. The detectivity values under IR light were 1.22 x 1010 Jones and 7.53 x 109 Jones for V= 0.0 volts (self -driven mode) and V= -2.0 volts, respectively.