Boundary condition model for the simulation of organic solar cells

Abstract

Organic solar cells (OSCs) are promising photovoltaic devices to convert solar energy into electrical energy. Their many advantages such as lightweight, flexibility and low manufacturing costs are intrinsic to the organic/polymeric technology. However, because the performance of OSCs is still not competitive with inorganic solar cells, there is urgent need to improve the device performance using better designs, technologies and models. In this work, we focus on the developing an accurate physics-based model that relates the charge carrier density at the metal-organic boundaries with the current density in OSCs using our previous studies on singlecarrier and bipolar diodes. The model for the boundary condition of the charge carrier density at the interfaces of OSCs follows a power-law function with the current density, both in dark and under illumination, and simulated current-voltage characteristics are verified with experimental results. The numerical simulations of the current-voltage characteristics of OSCs consider wellestablished models for the main physical and optical processes that take place in the device: light absorption and generation of excitons, dissociation of excitons into free charge carriers, charge transport, recombination and injection-extraction of free carriers.Our analysis provides important insights on the influence of the metal-organic interfaces on the overall performance of OSCs. The model is also used to explain the anomalous S-shape current-voltage curves found in some experimental data.

Device Physics of Hybrid Perovskite Solar cells: Theory and Experiment

“…As in other solar cells, the presence of traps can affect the PSC performance, modifying the magnitude of the current density and the shape of JV  curves. [150][151][152] Minemoto & Murata [153] identified the contribution of the defect density at the front interface to the hysteresis as much stronger than that at the back interface for large absorption coefficient materials (such as PSCs) without considering ion migration, though they did not implement dynamic scans. Other authors include both charge trapping and ion migration in numerical modeling, [4,62,63] where the distribution of ions can significantly alter the collection properties of the device.…”

Analysis of the Influence of Selective Contact Heterojunctions on the Performance of Perovskite Solar Cells

“…The set of transport equations for electrons, holes and ions have been numerically solved throughout the whole structure using, on the one hand, the typical boundary conditions at metal–semiconductor interfaces (see the Supporting Information) and, on the other hand, the boundary conditions at the CTL/perovskite interfaces, which impose the continuity of the potential, the current density and the electric displacement at the ETL/perovskite and perovskite/HTL heterojunctions. The continuity of electric displacement, D i , implies the following relations between the permittivity, ε i , and the electric field, F i : where the subindex, i = 1, 2, 3, indicates the layer: ETL → 1, perovskite → 2, and HTL → 3.…”

Degradation through Directional Self‐Doping and Homogeneous Density of Recombination Centers Hindered by 1,8‐Diiodooctane Additive in Non‐Fullerene Organic Solar Cells

“…The modification of the charge density profile in the No DIO samples before and after aging has also been approached in this work via DD modeling. A noncommercial home-made MATLAB code was developed in our previous works, [67,68] and adapted to the studied devices by considering the surface recombination currents as described by Kirchartz and Nelson [69] with optimal contact selectivity at each electrode. The used simulation parameters are listed in Table S2, S3, Supporting Information; the simulated J-V curves are shown with solid lines in Figure 1b and the simulated energy diagrams corresponding to the short-circuit condition are shown in Figure 3b,c.…”