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The challenge encountered by the sensor in practical application is that the optimal working temperature is high, which will cause certain dangers in the work. Herein, we fabricated a p-p heterojunction composite LaFeO 3 /YFeO 3 planar electrode sensor for gas detection. The planar electrode sensor adopts the method of direct heating, which reduces the optimal working temperature of the sensor compared with the traditional side-heated alumina ceramic tube sensor. The optimal operating temperature of the LaFeO 3 /YFeO 3 (0.8:0.2) planar electrode sensor is 110 °C. In addition, we also performed multi-wavelength (470, 420, and 370 nm) light illumination experiments on the LaFeO 3 /YFeO 3 sensor to improve gas response. Under 370 nm light illumination, the response values of the LaFeO 3 /YFeO 3 (0.8:0.2) sensor to 30 ppm methanol, acetone, and ethanol were 166.82, 199.58, and 292.67, which were 1.19, 1.33, and 1.36 times than those in the dark. The lowest detection limits of the LaFeO 3 /YFeO 3 (0.8:0.2) sensor under 370 nm light illumination for methanol, acetone, and ethanol were 0.3, 0.8, and 0.2 ppm, respectively. Therefore, the LaFeO 3 /YFeO 3 (0.8:0.2) planar electrode sensor has the advantages of small size, low optimal operating temperature, low power consumption, high response value to volatile organic compounds gases, and high-cost performance for use in different gas environments. • The LaFeO 3 /YFeO 3 (a:b) materials were fabricated by the sol-gel method. • Gas sensor was prepared using 1.5 × 1 mm plane electrodes. • The sensors were tested under multi-wavelength light illumination. • The optimal operating temperature of LaFeO 3 /YFeO 3 (0.8:0.2) sensor was 110 °C. • Light illumination improved the sensor's response to VOCs gases. [ABSTRACT FROM AUTHOR]