CsPbBr₃ single crystals （SCs） exhibit exceptional properties such as high atomic number， large carrier mobility-lifetime product， high resistivity， and excellent X/γ-ray absorption， making them promising materials for semiconductor radiation detectors. While solution-based methods enable cost-effective growth of CsPbBr₃ SCs， the resulting crystals often show a preferred orientation， rod-like shape and fast growth rates that lead to defects such as twinning， which hinder device fabrication. In this study， cetyltrimethylammonium bromide （CTAB） was introduced as an additive during inverse temperature crystallization to enhance crystal growth （it primarily decelerates the growth rate along the ［002］ direction， thus suppressing the preferential orientation of CsPbBr₃ SCs） and quality. The obtained CsPbBr₃ single crystal exhibits rocking curve full width at half maximum （FWHM） of 0.08°， a high resistivity of 8.14×10⁹ Ω·cm， an enhanced carrier mobility-lifetime product of 6.44×10^-3 cm²·V^-1， and a low trap density of 2.07×10¹⁰ cm^-3， indicating its high crystalline quality and electrical properties. Additionally， a γ-ray detector fabricated from the CsPbBr₃ SC achieved high performance， with an energy resolution of 10.25% for 59.5 keV γ-photons from a ²⁴¹Am isotope. These results highlight the potential of additive-assisted growth for producing high-quality CsPbBr₃ SCs for advanced radiation detection applications.