N-type CuGaSe2 single crystals are prepared using a co-doping technique with Ge and Zn. Employing this method electron concentrations in the range from 10(10) to 10(18) cm(-3) have been achieved. Magnetotransport measurements were carried out in the temperature range from 2 to 300 K. A critical concentration of 1.4 x 10(17) cm(-3) was found for the metal-insulator transition in n-CuGaSe2. Furthermore, at low temperatures a crossover from Mott- to Efros-Shklovskii-type variable range hopping is observed on the dielectric side of the transition. In addition, CuGaSe2 homojunctions have been prepared. Total area efficiencies as high as 8.9% are achieved under solar illumination.