Thermoelectric power, Hall coefficient and resistivity measurements were carried out on material cut from
monocrystalline ingots of CuInSe2. The ingots were grown using a vertical-Bridgman procedure, whereby Cu, In and Se
were melted and directionally cooled within a sealed quartz ampoule. When stoichiometric proportions of the starting
elements were used, the material was always p-type, with hole concentrations of the order of 1017-1018 cm-3. However,
the incorporation of a sufficient amount of sodium (0.3 at. %) into the melt was seen to result in n-type material, with
electron concentrations of the order of 1016. This conversion from p to n was hindered by the inclusion Se above
stoichiometry into the ampoule, and more Na was required for the material to change type. The mobility of the p-type
samples, with low sodium additions (0-0.2 at. %), was on average 17 cm2V-1s-1, and was seen to be higher for material
grown from melts containing excess Se, corresponding to the chemical formula CuInSe2.2, than from stoichiometry.
SEM/EDX (Scanning electron microscope / Energy-dispersive X-ray spectroscopy) analysis of the ingots after growth
indicated no sodium residing within the interior of the bulk material, but a significant amount was found on the exterior
surface in the case of an ingot grown with CuInSe2.05 and 5 at. % Na. Various deposits found within the ampoules after
growth were analyzed, including a copper-rich precipitate found only in ampoules which included a high concentration
of Na and a low concentration of excess Se, resulting in n-type material.