Piezoelectrics with their permanent polarization and its change with temperature can be used to enhance optoelectronic properties of semiconductor devices. Here we present several exemplary devices to illustrate the benefits of piezoelectric substrates. The first example is an optothermal field effect transistor (FET) based on the pyroelectric effect of the piezoelectric substrates. The device is a graphene-lead zirconate titanate (PZT) system utilizing the high optical transparency and conductance of graphene.1 Under the incidence of an infrared (IR) laser beam, the drain current can be increased or decreased depending on the direction of the polarization of the PZT substrate. The drain current sensitivity of the optothermal FET can reach up to 360 nA/mW at a drain field of 6.7 kV/m more than 5 orders of magnitude higher than that of the photogating transistors based on carbon nanotube on SiO2/Si substrate. A similar device using single zinc oxide nanowire and PZT (ZnO NW�PZT) was also demonstrated.2 Recently, we combined the transparent and conductive properties of graphene with the optical and photovoltaic properties of Poly(3-hexylthiophene) (P3HT) as a hybrid composite.3 Based on the inherent nature of the band alignment between graphene and P3HT, the photogenerated holes are able to transfer to the graphene layer and improve the photoresponse. When the graphene was deposited on a piezoelectric Pb(Zr0.2Ti0.8)O3 (PZT) substrate, the photoresponse of such composite photodetectors was found to be ten times larger than on SiO2 substrate. It was demonstrated that the electric field of the polarization of piezoelectric substrate helped the spatial separation of photogenerated electrons and holes and promoted the hole doping of graphene to enhance the photoconduction. Moreover, with the replacement of P3HT by a thin layer of bulk heterojunction of polymer and fullerene, the photosensitivity can be further increased by more than one order of magnitude. More recently, we replaced the P3HT with graphene quantum dots (GQDs). Preliminary results showed that the photoresponse of the GQD-graphene composite on PZT was even higher than that of P3HT-graphene system. More updated results will also be presented. References C.-Y. Hsieh, Y.-T. Chen, W.-J. Tan, Y.-F. Chen, W. Y. Shih, and W.-H. Shih, �Graphene-PZT Optothermal Field Effect Transistors,� Appl. Phys. Lett., 100, 113507 (2012) C.-Y. Hsieh, M.-L. Lu, J.-Y. Chen, Y.-T. Chen, Y.-F. Chen, W. Shih, and W.-H. Shih, "Single ZnO nanowire-PZT Optothermal Field Effect Transistors," Nanotechnology, 23, 355201 (2012) W.-C. Tan, W.-H. Shih, and Y.-F. Chen, �Highly Sensitive Graphene-Organic Hybrid Photodetector with Piezoelectric Substrate,� Advanced Functional Materials, DOI: 10.1002/adfm.201401421