Sustainable light energy from ambient environment has attracted particular attention to meet the ever-growing need of small-scale electronics. The modulation of intercorrelated thermal and electronic transport is one of the crucial aspects for reliable photothermoelectric electronics. Herein, a defect-promoted photothermoelectric effect is demonstrated in densely aligned ZnO nanorod array with rich lattice defects. The defect-rich ZnO device delivers high electrical conductivity and large Seebeck coefficient to enable significant improvement of photothermoelectric energy conversion and self-powered photodetection. The position sensitivity reaches approximately 0.19 mV mm−1, and the temperature gradient induced electric field makes up for the suppression in the photothermoelectric process. The synergism between intrinsic defects and extra temperature field plays an important role in promoting the photothermoelectric properties of dense ZnO nanorod array. This study is interesting for interpreting the thermo-phototronic phenomena as well as demonstrating the possibility of defect engineering and phonon engineering to enable highly efficient light energy scavenging and self-powered photodetection.