Meeting the challenge of direct electrically driven organic semiconductor lasers (OSLs), the design of OSL materials is being studied. Polarized species generally exist in conjugated organic materials and play an important role in the photophysics procedure; therefore, understanding these species is beneficial for designing novel OSL materials. Here, we use the amplified spontaneous emission effect as a medium to reveal a carbazole-benzothiadiazole-based polarized species induced by a charge transfer process. Spectroscopic analysis confirms that this polarized species that acted as a CT pair defect has a negative influence on the ASE stability and solid state fluorescent quantum yield. This inspires us to be cautious in terms of some specific molecular group combinations when designing OSL materials.