High-Efficiency Sequential-Cast Organic Solar Cells Enabled by Dual Solvent-Controlled Polymer Aggregation

The precise tuning of the active layer morphology to improve organic solar cells (OSCs) efficiency remains a key issue in the field of organic photovoltaics. Herein, a new solution to the above problem is provided by using the dual-solvent modulated polymer-assisted sequential spin-coating method. Herein, the sequential spin-coated OSCs based on the D18-Cl/Y6 system are prepared for the first time and an efficiency of 16.38% is obtained, similar to that of bulk heterojunction OSCs. On this basis, the performance is further improved by using a dual solvent to balance the dissolution and crystallization of D18-Cl, separately optimizing the morphology of the donor layer and allowing the subsequent spin-coated Y6 solution to penetrate uniformly into the D18-Cl framework. After the dual-solvent treatment, the D18-Cl (CF+ CB)/Y6-based device obtains a power conversion efficiency (PCE) of 17.33% and the D18-Cl (THF+ CB)/Y6-based device achieves an even better PCE of 17.73%. It is worth noting that no post-treatment is adopted here and after 2500 h of placement, the efficiency of the aforementioned devices is still 90% of the original. Thus, this work provides a simple method for tuning the film morphology to prepare efficient and stable devices, which is beneficial for future commercial production of OSCs.

Automated summary

The study proposes a dual-solvent modulated polymer-assisted sequential spin-coating method to improve the efficiency of organic solar cells (OSCs). By optimizing the morphology of the donor layer and achieving uniform penetration into the D18-Cl structure, the performance of the OSCs can be further improved. The results demonstrate that this method can prepare efficient and stable OSCs.