RESUMEN
This study underscores the significance of precisely manipulating the morphology of the active layer in organic solar cells (OSCs). By blending polymer donors of D18 with varying molecular weights, a multiscale interpenetrating fiber network structure within the active layer is successfully created. The introduction of 10% low molecular weight D18 (LW-D18) into high molecular weight D18 (HW-D18) produces MIX-D18, which exhibits an extended exciton diffusion distance and orderly molecular stacking. Devices utilizing MIX-D18 demonstrate superior electron and hole transport, improves exciton dissociation, enhances charge collection efficiency, and reduces trap-assisted recombination compared to the other two materials. Through the use of the nonfullerene acceptor L8-BO, a remarkable power conversion efficiency (PCE) of 20.0% is achieved. This methodology, which integrates the favorable attributes of high and low molecular weight polymers, opens a new avenue for enhancing the performance of OSCs.
RESUMEN
Efficient charge transport and extraction within the active layer plays a major role in the photovoltaic performance of organic solar cells (OSCs). In this work, the spontaneously spreading (SS) process was utilized to achieve sequential deposition of the active layer with a planar heterojunction (PHJ) structure. The SS process avoids the damage of the upper layer solution to the lower layer film by the spin coating process. The film with PHJ structure exhibits notable vertical phase separation compared to the bulk heterojunction (BHJ). Moreover, the power conversion efficiency (PCE) of the PHJ device (12.00%) is significantly higher than that of the BHJ (10.84%) due to the efficient charge transport. This work offers a novel fabrication method and device structure to enhance the photovoltaic performance of OSCs.