High-Efficiency Layer-by-Layer All-Polymer Solar Cell Enabled by Bottom-Layer Optimization

All-polymer solar cells (all-PSCs) have attracted extensive attention for their advantages in long-term thermal- and photostability. However, the power conversion efficiencies (PCEs) of all-PSCs still lag behind organic solar cells based on small-molecular acceptors. The long-chain entanglement between polymers brings complex morphological problems, which contribute to lower fill factor (FF). Herein, an effective approach is proposed to build the ideal morphology and pseudo-p-i-n vertical component distribution in all-polymer active layer by independently casting donor and acceptor films with different solvents. Through the solvent engineering, the layer-by-layer device with o-xylene and carbon disulfide (O-XY:CS2)-processed D18 donor layer achieves a PCE of 17.53%, much higher than commonly used solvents (chloroform and chlorobenzene) processed donor layers with PCEs of 16.49 and 16.04%, respectively. In-depth investigation reveals that outstanding performance of O-XY:CS2-processed donor layer device is attributed to mitigated bimolecular recombination, more balanced mobility, and reduced trap density of states, which contribute to the enhancement of short-current density and FF. Moreover, favorable morphology network also brings prolonged lifetime under continuous light soaking. This work presents a simple and effective way to obtain ideal active layer morphology and construct favorable vertical component distribution through optimizing donor morphology in all-PSCs. A simple and effective way to obtain an ideal pseudo p-i-n structure via optimizing donor morphology and constructing favorable vertical component distribution in all-polymer solar cell is demonstrated. Through solvent engineering, a higher power conversion efficiency (17.53%) has been achieved in layer-by-layer devices with donor D18 processed by o-xylene and carbon disulfide, higher than chloroform (16.49%) and chlorobenzene (16.04%).image & COPY; 2023 WILEY-VCH GmbH

Automated summary

An effective approach to achieving ideal active layer morphology and favorable vertical component distribution in all-polymer solar cells is demonstrated. This is done through solvent engineering and independent casting of donor and acceptor films using different solvents. The layer-by-layer device with o-xylene and carbon disulfide (O-XY:CS2)-processed D18 donor layer achieves a higher power conversion efficiency (17.53%) compared to commonly used solvents (chloroform and chlorobenzene) processed donor layers (PCEs of 16.49% and 16.04% respectively). This work provides a simple and effective method for optimizing donor morphology and constructing a favorable pseudo p-i-n structure, leading to improved performance in all-polymer solar cells.