Often referred to as “nanoscale earthquakes”, surface acoustic waves (SAWs) are elastic waves which propagate on the surface of a solid at the speed of sound. A voltage signal applied to comb-like metal electrodes, termed as interdigital transducer, generates SAW on a piezoelectric substrate. The applications of SAWs are wide spanning from electronics, optics, microfluidics, medical diagnostics or mobile communication and even quantum technologies [1]. While interacting with a semiconductor, the strain and piezoelectric fields of SAW modulate the semiconductor band structure. Strain-induced field imposes an acoustoelectric (AE) drag on the charges in the direction of SAW propagation, and when paired with an optically-active semiconductor, excitons can be ionized by piezoelectric field into separate electrons and holes, captured and transported by the SAW towards an output spot [2]. Utilizing these effects, first-of-a-kind organic polymer, poly(3-hexylthiophene) (P3HT) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenvinylen] (MEH-PPV) based charge transport devices [3-4] and excitonic transistor [5] have been demonstrated, opening up the integration of acoustic charge transport with emerging low cost and solution processable semiconductor systems.
Here, we present the first study of the SAW-induced charge transport in hybrid organic-inorganic semiconductor system. This system comprises P3HT and halide perovskite (CsPbBr3 and CsPb(IxBr1-x)3) nanowires (NWs). We observe a pronounced AE effect driven by the SAW. The AE current can be efficiently gated by optical excitation using a focused green laser. Initially, we show that in reference samples with only halide perovskite NWs the total AE current nearly vanishes due to comparable mobilities for electrons and holes in these materials [6]. In strong contrast, in devices with hybrid layers, a weak AE effect is observed for CsPb(IxBr1-x)3 NWs and a hole dominated AE transport for CsPbBr3 NWs. These observations can be explained by the band alignment at the interface between LUMO between the P3HT and the perovskite. While for CsPb(IxBr1-x)3 -P3HT ambipolar electron and hole transport occurs in the perovskite, for CsPbBr3-P3HT, electrons are transferred to the low electron mobility in P3HT, inhibiting electron-mediated AE transport.
References
[1] P. Delsing et al., J. Phys. D: Appl. Phys. 52, 353001 (2019).
[2] P. Bhattacharjee et al., J. Phys. D: Appl. Phys. 57, 423001 (2024).
[3] H. Mishra, et al., J. Phys. D: Appl. Phys. 56, 015102 (2022).
[4] P. Bhattacharjee, et al., J. Appl. Phys. 133, 195501 (2023).
[5] P. Bhattacharjee, et al., ACS Appl. Electron. Mater., 5, 3650–3656 (2023).
[6] L. Janker et al., Nano Lett., 19, 8701−8707 (2019).