This paper presents a novel approach on diode model parameter identification from the I- V characteristics of photovoltaic panels. Other than the prevailing methodology of solving a group of nonlinear equations from a few points on the I-V curve, the proposed methodology views the diode model as the equivalent output of a dynamic system. From this new viewpoint, diode model parameters are linked to the transfer function (after Laplace transform) of the same dynamic system whose parameters are then identified by a simple integral-based linear square. The indoor flash test shows the accuracy and effectiveness of the proposed method, and outdoor module testing shows its ability of online monitoring and diagnostics. Comparisons to the methods of Lambert W function and evolution algorithms are also included.