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The thin film morphology of double-cable conjugated polymers is critical to the performance of single-component organic solar cells (SCOSCs). Here, we explore the effect of thin film crystallinity on device performance by varying the thermal annealing temperature used during device fabrication. Our investigations reveal that a moderate annealing temperature of 150 °C optimizes the power conversion efficiency in SCOSCs. Although higher annealing temperatures leads to increased crystalline order, a decrease in device performance is observed, attributed to imbalanced carrier transport and increased charge recombination. Additionally, the progressive decrease in the open-circuit voltage of these cells with increasing annealing temperature is linked to augmented non-radiative voltage losses, stemming from the increase in film crystallinity. This study underscores the critical necessity of achieving a delicate optimization of film microstructure in order to maximize the efficiency of SCOSCs, while also delineating prospective avenues for refining the molecular design and processing of double-cable polymers to bolster solar cell performance.
Zhang et al. (Mon,) studied this question.