Study of the series resistance evolution in organic solar cells by use of the Lambert W function

The time evolution of the series resistance of bulk heterojunction solar cells realized and stored in inert atmosphere as well as in air has been monitored by fitting the experimental current v s . voltage characteristic to the analytical solution of the real diode equation obtained by means of the Lambert W function. The method allows to determine if and at what extent the standard one diode model can be used to acceptably describe the organic device in the field of a preliminary simple and fast evaluation of the series resistance evolution with time, without the need of complex and time consuming numerical fitting algorithms.