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

Ultrathin PEDOT:PSS film induces inversion layer within Si to achieve carrier separation, but it as the windowlayer 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.

Automated summary

The management of reflectivity and parasitic absorption by adjusting the thickness of PEDOT:PSS film can improve light absorption of the active layer, thereby enhancing the performance of solar cells. Additionally, increasing the PEDOT:PSS film thickness can gradually weaken the quasi-Fermi level bending, stabilize hole concentration, and improve carrier separation efficiency to reduce carrier recombination. The power conversion efficiency (PCE) can reach 12.35% through applying the optimized rule obtained from simulation to the experiment, a 30% improvement compared to unoptimized PEDOT:PSS/Si hybrid solar cells.