All simulation techniques of the relationship between output current and output voltage contain an implicit function before this work. Thus, understanding the relationship between current and voltage using an analytically invertible function is a key method of any predicative for designer in photovoltaic system. This paper develops a technique for determining the light generated current-voltage (I-V characteristic of cell using a valid analytically invertible function. The technique neither involves any initial approximations nor iteration processes. The technique is employed for four experimental results of PV cells, Obtained I-V characteristics for the cells using the present technique are in well agreement with those of reported in the measurements. Meanwhile, the electric power is linked with voltage based on this approach so that the voltage at the maximum electric power point becomes predicative. In addition, the voltage at the maximum electric power point can be forecasted via irradiance. Moreover, the mathematical method of irradiance dependent on the reverse saturation current is found. All results confirm the analytically invertible function as a useful tool at the reliable comprehension on PV devices. (C) 2015 Elsevier Ltd. All rights reserved.