A flexible pyro-phototronic nanogenerator based on the surface-polarization effect

Abstract

In this work, an organic pyro-phototronic nanogenerator device has been fabricated on a flexible substrate. Rubrene, an organic semiconductor, shows pyroelectricity due to the surface polarization effect, despite its centrosymmetric structure. The pyroelectric contribution of the material was studied under different illumination intensities and compared to the overall pyro-phototronic current generation. This thin film organic pyro-phototronic device was explored as a flexible nanogenerator. The device was bent periodically over an increasing number of bending cycles, up to a total of 600. The temporal response of the pyro-phototronic current and voltage as outputs reveal the influence of the bending on the generation of charge carriers. Overall device performance parameters like pyroelectric current generation and surface power generation were studied in detail revealing the effects of the bending cycles. The surface power density of the nanogenerator before bending is found to be 65.6 nW m⁻², which increases up to 107 nW m⁻² after 200 bending cycles. However, the performance of the nanogenerator device reduces after subsequent bending cycles and settles at an appreciable value of 84 nW m⁻² after 600 cycles. The reduction of the power density at higher numbers of bending cycles is attributed to deformation of the thin film layers. This work reveals the potential applicability of surface-polarization-induced flexible pyro-phototronic nanogenerators in future advanced devices.