Fig. 4
![Fig. 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs11671-016-1499-1/MediaObjects/11671_2016_1499_Fig4_HTML.gif)
Schematic band diagrams of a CuI/ZnO heterojunction a without and b with compressive strain to illustrate the working mechanism of piezo-phototronic effect-enhanced PD performance; c photocurrent ΔI, d photoresponsivity R, and e relative changes of photoresponsivity R/R 0 and f the detectivity D* of CuI/ZnO PD under different strain and illumination conditions, biased at 1.5 V