New process for synthesizing crystalline Rubrene useful for optoelectronic devices

Since last few years, scientists from around the world are working on the synthesis of organic materials for electronic applications. Conventional process for synthesis of organic electronic materials based on chemical processes provides very good quality materials, but the stability of the materials is not very good and it requires use of solvents. Moreover, multiple steps are required for material synthesis and film deposition. To overcome these challenges IASST team has been working on plasma based process due to the unique advantages of such process over the conventional processes of organic electronics.

The new synthesis is a water-free, environmentally friendly one-step plasma process. A highly uniform pin-hole-free thin film can be deposited by this process which is useful for fabrication of high-end devices. According to the IASST team, formation of crystalline rubrene at sufficiently high Radio Frequency (RF) plasma power confirmed that with increasing applied RF power, a phase transition from amorphous to crystalline rubrene can be obtained. The oxide layer over the crystalline rubrene film that causes surface polarization, is formed after exposure of the deposited film in air due to film surface oxidation, which results in the device to work in pyro-phototronic mode.

This work delivered a new experimental approach for synthesis of crystalline rubrene film and realization of pyro-phototronic effect on a fully organic crystalline medium with rubrene for the first time. It also circumvents the essentiality of materials to be non-centrosymmetric crystal to show pyroelectric behaviour. This novel process developed by IASST team besides being useful for developing advanced optoelectronic devices and preparation of Electronic Skin (E-Skin), may be useful as a tool for laboratory simulation of different biological systems for probing the organization and dynamics of those systems.


Figure 1: Material synthesis process, device layout and current versus time plots of the pyro-phototronic device. PPA-CRB: Plasma Polymerizes Aniline – Crystalline Rubrene, ITO: Indium Tin Oxide, I­PV: Current due to photovoltaic effect, IP: Current due to pyro-phototronic effect

Publication: Deepshikha Gogoi, Amreen A Hussain, Sweety Biswasi and Arup R Pal, Journal of Materials Chemistry C, 8 6450 (2020).

Patent: A process for synthesis of crystalline rubrene incorporated thin film, Arup R. Pal, Amreen A. Hussain and Deepshikha Gogoi, Indian Patent, Application No. 201931016529 filed on 25-04-2019.