2-Dimensional optoelectronic simulation for nanostructured organic-inorganic hybrid solar cells

Hybrid solar cells (HSCs) based on a mixture of organic and inorganic semiconductor materials attract a lot of attention owing to the combination of desirable properties of both materials. Due to low exciton diffusion length and light harvesting issues, nanostructures are often employed in HSCs. However, most numerical models over-simplify the complicated bulk heterojunction (BHJ) into a homojunction configuration which losses insights to charge transport. Moreover, designing nanostructures to achieve both light harvesting and carrier collection is essential, but rather complicated. In this work, we develop a methodology based on two-dimensional (2D) optical and electrical simulations which are tailored for the hybrid system. The optical simulation employs a finite-difference time-domain (FDTD) technique to calculate the electromagnetic field and obtain the generation rate in the nanostructure. Next, an electrical calculation is based on a 2D self-consistent drift-diffusion and Poisson solver which uses a finite element method (FEM). As a result, our works allows the analysis of optical and electrical properties of nanostructured heterojunction semiconductor materials. The theoretical approach has been validated for P3HT/PCBM BHJ organic solar cells. In this study, hybrid structures based on Si nanowires (NWs)/ poly(3-hexylthiophene)(P3HT) are used as the hypothetical material system, where an interpenetrating network of rectangular channels consisting of SiNWs and P3HT is assumed. The simulation results show that NWs facilitates transmission and absorption of sunlight inside the photoactive layer. We then investigate the device current-voltage characteristics as a function of the recombination rate, barrier heights of anode and cathode, and structural configuration of interfaces. The theoretical approach also allows the optimization of optical and electrical properties of solar cells with embedded nanostructures or nanoparticles.