Performance analysis of organic solar cells: Opto-electrical modeling and simulation

In this paper, the effect of mobility and active layer thickness on the properties of bulk heterojunction solar cells have been investigated using the drift-diffusion model. It was observed that open circuit voltage and power conversion efficiency are affected by two loss mechanisms. The recombination of charge carriers in wrong contacts destroys photogenerated electron-hole pairs, and the bulk recombination increases the act of coupling between electron-hole pairs with different binding energies and consequently lowers the open circuit voltage. The first loss mechanism rises as the mobility of each of the two carriers increases. The bulk recombination not only depends on the slow carrier mobility but also affected by the mobility balance of two carriers. Thus, it generates two optimal points for power conversion efficiency at none unity electron to hole mobility ratio. In the active layer, light does not get absorbed uniformly, and the profile of the photogenerated excitons depends on the device thickness. Therefore, similar changes in the electron and hole mobility do not bring about the same changes in power conversion efficiency. Also, this study indicates that with the simultaneous increase of mobility and thickness, considerable enhancement in the efficiency of the bulk heterojunction solar cells would be achieved. (C) 2020 Karabuk University. Publishing services by Elsevier B.V.

Automated summary

This study investigates the impact of mobility and active layer thickness on the properties of bulk heterojunction solar cells using the drift-diffusion model. It reveals that open circuit voltage and power conversion efficiency are affected by two loss mechanisms, as well as the uneven absorption of light and distribution of photogenerated excitons in the active layer. The study suggests that simultaneous increase in mobility and thickness can significantly enhance the efficiency of bulk heterojunction solar cells.