An Analytical Solution to Lumped Parameter Equivalent Circuit Model of Organic Solar Cells

Abstract

In this paper, an analytical and closed-form solution to the lumped parameter equivalent circuit model of organic solar cells is proposed to complete the simulations of the S-shaped I-V characteristics. Based on the model previously proposed by Mazhari, the set of terminal current and voltage equations describing the three diodes is solved and the effects from the model parameters are illustrated. Our solutions are verified by being compared with the least square method results and experimental data, respectively. Good agreements show that our solution calculation scheme is not only both accurate and efficient, but also valid in the whole operation regime of solar cells, especially for the S-shaped kink on the condition where the terminal voltage is larger than the open circuit voltage. Such an analytical solution can play an important role in the simulations for I-V characteristics of solar cells, fast extractions of the model parameters, and implements into practical photovoltaic device simulators.

An Improved Organic Solar Cell Lumped-Parameter Equivalent Circuit Model

“…Compared with Mazhari's model, the simulation results of our improved model for Sshaped kink are more accurate in the third quadrant. Finally, we used the least square method and For the solar cells in Reference [19], the enhanced electron acceptor (fullerene C60) and donor (purified Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene]) bilayer films were prepared on clean ITO glass coated with 50 nm of PEDOT:PSS and 50 nm of Al cathode, with the aim of increasing the power conversion efficiency (PCE). In the N 2 atmosphere, the solar cells in [19] were exposed to 1000 W/m 2 simulated AM1.5G sunlight, and the I-V characteristics were measured and shown as symbols in Figures 9-13.…”

“…In Figures 9-13, we compare the solutions of our improved model with experimental data [19] to verify our model in practice. Simultaneously, the results simulated by Mazhari's model are shown in Figures 9-13, which may be compared with our improved model.…”

“…We use the Newton-Raphson root-finding scheme [19], as a trade-off method between accuracy and efficiency, to derive an analytical solution of Equation (1) obtaining the computation results of V int as a function of V. Subsequently, we substitute V int into Equation (2) to get the results of the I-V equation in Figure 2. It is noted that the Newton-Raphson root-finding scheme adopted in solving Equation (1) processes the fast convergence and enough computation accuracy.…”

“…Among the multiple-diode equivalent circuit models [11][12][13][14][15][16][17], Mazhari's model [11] is regarded as the simplest model including seven parameters used in simulations, while the other models [12][13][14][15][16][17] contain at least eight fitting parameters. Mazhari's model is able to provide an electrical explanation [18] of the OSC S-shaped kink with exponential-like rise in the first quadrant, but it fails to demonstrate the linear-like rise of the S-shaped kink of OSCs in the third quadrant [19].…”

“…Simultaneously, the results simulated by Mazhari's model are shown in Figures 9-13, which may be compared with our improved model. [19] with annealing at 120 °C. Figure 10.…”