Correlation between molecular configuration and charge transfer dynamics in highly efficient organic solar cells

Songlin Zhan,Qicong Li,Furui Tan,Cheng Yang,Yulin Wu,Xiaohao Jia,Chao Li,Kong Liu,Shengchun Qu,Zhijie Wang,Zhanguo Wang

doi:10.1016/j.jpowsour.2022.231351

Songlin Zhan, Qicong Li + Show 9 more

https://doi.org/10.1016/j.jpowsour.2022.231351

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Molecular design and charge transport dynamics play an important role in achieving highly efficient organic solar cells (OSCs). In this work, non-fullerene acceptor Y6, its alkyl chain modified derivative N3 and halogen-replaced derivative BTP-BO-4Cl are selected to fabricate OSCs. The OSCs obtain a high power conversion efficiency (PCE) of 16.86%. The impact of different modification methods on molecular configuration and energy level matching is investigated systematically by time-resolved photoluminescence (TRPL) and transient absorption spectroscopy (TAS). The results demonstrate that side chain modification has a positive effect on molecular layer spacing, domain area size and charge carrier mobilities. More importantly, halogen atom replacing has the similar but more positive impact, bringing a higher PCE than side chain modification. The overall processes of charge generation, dissociation and recombination in OSCs are studied systematically for the first time. For the best-performance device, the lifetimes of singlet exciton recombination (τ1), charge transfer (CT) state recombination (τ2), singlet exciton dissociation (τ3) and CT state dissociation (τ4) are calculated as ∼500 ps, ∼2 ns, ∼200 fs and ∼1 ps, respectively. The correlation between molecular configuration and charge transfer dynamics is established, which can provide a guideline for designing materials of highly efficient OSCs.

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