The results of numerical device simulations for p-i-n diodes and the closed-form expression of the current-voltage characteristics developed for p-n diodes are compared. It is shown that the closed form expression correctly predicts the functional relationship between material parameters and device performance of p-i-n diodes. The ideality factor between 1 and 2 is analyzed in detail. The effect of the defect density, the intrinsic carrier concentration, the mobility and the built-in potential on device performance are demonstrated. These insights are applied to analyze microcrystalline silicon thin-film solar cells deposited by chemical vapor deposition at temperatures below 250 degrees C. (c) 2006 Elsevier B.V. All rights reserved.