Improving light absorption of active layer by adjusting PEDOT:PSS film for high efficiency Si-based hybrid solar cells

Abstract Ultrathin PEDOT:PSS film induces inversion layer within Si to achieve carrier separation, but it as the window-layer directly affects the light absorption. Herein, we show that management of reflectivity and parasitic absorption by adjusting PEDOT:PSS film thickness improves light absorption of active layer. According to the equivalent optical admittance theory and the finite element method, it is found that the reflectivity spectrum is divided into periodic and aperiodic regions by a certain wavelength threshold. When the threshold is close to 300 nm, the smaller reflection and parasitic absorption can be achieved. Meanwhile, with the increase of PEDOT:PSS film thickness, the quasi-Fermi level bending gradually weakens, and the hole concentration gradually keeps stable. This improves the carrier separation efficiency to reduce the carrier recombination, which ensures the improvement of solar cell performance. Finally, the power conversion efficiency (PCE) of 12.35% is obtained by applying the rule obtained from the simulation to the experiment, which is 30% higher than that of the unoptimized PEDOT:PSS/Si hybrid solar cell.