The self-powered photodetectors (PDs) have gained much attention due to they do not require additional external energy and can be well applied in distributed optoelectronic detection networks. However, the small built-in electric field and rich interface states of self-powered PDs, make it a severe challenge to achieve large linear dynamic range (LDR) and high responsivity. Herein, a n-Si/n-ZnO heterojunction structure self-powered PD is constructed, fully utilizing the characteristics of transient current less affected by the excitation power and interface states, and using transient current as the detection signal significantly improves the PD’s photocurrent responsivity (R) and the LDR. Under the excitation of 365, 530, 660 and 970 nm light, the device’s maximal peak-to-peak transient current responsivity (R_tt’) values are 89.3, 341, 439 and 542 mA W^-1. The device’s corresponding LDR is 113.8, 112.5, 105.9 and 74.6 dB, which are 25.9, 29.9, 20.3 and 14.4 dB higher than steady-state current (I_s), respectively. Furthermore, in the presence of background light, the device’s transient current exhibits enhanced light intensity change resolution and background light interference resistance. Finally, the 6×6 detector array’s transient current (I_t) response has a good consistency and LDR, which significantly improves the device’s imaging quality and resolution. This work provides new ideas for improving the R and LDR of self-powered PDs, and will promote the development and application of transient current responsive self-powered PDs in the fields of high-sensitivity detection and fast imaging.