A method to control the grain size of CdTe thin films deposited by close space sublimation using chamber pressure is demonstrated. Grain diameter is shown to increase in the pressure range 2-200 Torr, following the linear relationship D (mu m)=0.027 x P (Torr)+0.90. A mechanism is proposed to explain the dominance of the 111 preferred orientation in the small-grained, but not the large-grained films. For a series of CdTe/CdS solar cells in which the only variable was grain size, the performance parameters were seen to increase from 0.54% (0.94 mu m grains) up to a plateau of 11.3% (>= 3.6 mu m grains). This corresponds to the point at which the series resistance is no longer dominated by grain boundaries, but by the contacts. (C) 2010 Elsevier B.V. All rights reserved.