Sensing from the ultraviolet to the infrared is important for a number of scientific and industrial applications. Poly(4-vinyl pyridine) swollen in liquid pyridine functions as a photoconductive gel sensitive to irradiation in the ultraviolet. By blending poly(4-vinyl pyridine) with poly(4-vinyl pyridine-co-butyl methacrylate), we have now succeeded in expanding the range of wavelength sensitivity of the gel to cover the whole visible spectrum. Furthermore, addition of a small amount of 4-hydroxypyridine to the polymer blend results in unusually high thermal sensitivity (TCR = (0.1–0.16)/1 °C). Spectroscopic measurements show that the combined processes of proton transfer and electron transfer, occurring in a DC electric field, contribute to the gel properties. The optimized system has potential application as a simple and inexpensive active layer in organic photovoltaic cells as well as a thermal sensor.