Organic field-effect transistors (OFETs) have emerged as promising sensors targeting chemical analytes in vapors and liquids. However, the direct detection of solid chemicals by OFETs has not been achieved. Here for the first time, we describe the direct detection of solid chemical analytes by organic electronics. An organic diode structure based on a horizontal side-by-side p-n junction was adopted and shown to be superior to OFETs for this purpose. The diodes showed more than 40% current decrease upon exposure to 1 ppm melamine powders. The estimated detection limit to melamine can potentially reach the ppb range. This is the first demonstration of an electronic signal from an interaction between a solid and an organic p-n junction directly, which suggests that our lateral organic diodes are excellent platforms for the development of future sensors when direct detection of solid chemicals is needed. The approach developed here is general and can be extended to chemical sensors targeting various analytes, opening unprecedented opportunities for the development of low-cost and high-performance solid chemical sensors.