Effects of the Cu variation in CuxZnSnSe4 (CZTSe) bulks with x = 1.4-2.2 on the morphological, structural, and electrical properties has been investigated. Dense CZTSe pellets with grains of 2-5 mu m were obtained. All CZTSe pellets showed a p-type behavior with a carrier concentration of 10(16)-10(19) cm(-3). CZTSe at x = 1.8 and 2.0 has a high mobility above 25 cm(2)/V s and an un-favored hole concentration above 10(18) cm(-3). Although CZTSe at x = 1.6 has a low hole concentration of 1.5 x 10(17) cm(-3), its mobility is below 2 cm(2)/V s. The contradiction has made the CZTSe solar cell device with a low efficiency. The explanation, based upon vacancies and antisite defects, for the changes in electrical property is supported by the data from lattice parameter. The study in bulk CZTSe and its defects is helpful as they are applied to the fabrication of thin-film solar cell devices. (C) 2013 Elsevier Ltd. All rights reserved.