As expected, the detectors’ performance prepared by the hydrothermal method is much higher than that prepared by a low-temperature solution process. The former one has a lower dark current (1.22 nA) and a higher photon response (3.06 nA), while the latter has a higher dark current (6.08 nA) and a lower photon response (0.88 nA) (Fig. 3(b)). Figure 3(c) shows the response pattern of the hydrothermal device with the X-ray dose rate from 5499 to 785 μGy
air/s by changing the current of the X-ray source from 140 to 20 μA at a constant DC bias of 5 V. It should be noted that the contribution of air ionization can be ignored because of the considerable difference between the response of air ionization and that of our device (Fig. S4). Here, we consider that the electrode area size is 0.1 cm
2. We can estimate the ray detection sensitivity under different bias voltages by linear fitting according to this data. The result is reported in Fig. 3(d). The X-ray detection sensitivity of the Ba
2AgIO
6 device is calculated to be about 4.05 μC/(Gy
air·cm
2) at 1 V bias (about 1 V/mm) and 18.9 μC/(Gy
air·cm
2) at 5 V bias (about 5 V/mm). We further compared the responses of wafers with different thicknesses (Table S2). According to Fig. 1(b), the 0.7 mm thickness of Ba
2AgIO
6 is sufficient to absorb 99% of X-rays. Therefore, the 0.5 mm-thick wafer cannot fully absorb X-rays, resulting in a significant loss of sensitivity. For a 2 mm-thick wafer device, photogenerated carriers cannot reach both ends of the electrode due to the poor charge transportability of our Ba
2AgIO
6 wafer, leading to the decrease of our device’s sensitivity. After considering factors such as X-ray absorption and charge transfer, We obtained the optimal X-ray sensitivity of 18.9 μC/(Gy
air·cm
2) at 5 V of the device at 1 mm thickness. The sensitivity is very close to commercial α-Se X-ray detectors (20 μC/(Gy
air·cm
2)) [
17]. Its relatively good sensitivity and non-lead toxicity fully demonstrate its application in X-ray detection.