A molecular weight-regulated sequential deposition strategy enabling semitransparent organic solar cells with the light utilization efficiency of over 5%

The compromise between power conversion efficiency (PCE) and average visible transmittance (AVT) poses a big challenge for high performance semitransparent organic solar cells (ST-OSCs). Herein, a molecular weight-regulated efficient sequential deposition (SD) strategy is first employed to improve the performance of ST-OSCs. A series of narrow bandgap (NBG) polymer donors PCE10-2F with different molecular weights have been synthesized. A molecular weight-regulated SD strategy has been discovered to fine-tune the crystallinity of the polymers, not only favoring the formation of a dense and robust film, but also reasonably adjusting the compatibility of donors/acceptors to enhance interfacial contact. Thanks to the favorable morphology, efficient charge dynamics, and suppressed energy loss, a record PCE of 14.53% is obtained for the PCE10-2F/Y6 all-NBG materials-based opaque device. Optical simulations reveal that the SD process favors a convenient and precise control of individual layers for the optimization of light transmission. The corresponding ST-OSC achieves a breakthrough PCE of 11.11-10.01% with a high AVT of 39.93-50.05%. A champion light utilization efficiency (LUE) of 5.01% is achieved for ST-OSCs without complex optical engineering, demonstrating the successful balance of PCE and AVT. These results demonstrate that the molecular weight-regulated SD method is a facile and promising strategy for highly efficient ST-OSCs.