Rational tuning of intermolecular and intramolecular interactions enabling high-efficiency indoor organic photovoltaics

Indoor organic photovoltaics (IOPVs) are one of promising candidates for transferring artificial illumination to power the Internet of Things (IoT). However, their power conversion efficiencies (PCE) are limited by the fact that only a few efficient non-fullerene acceptors are available for IOPVs. Herein, new strategy is adopted to tune the intramolecular charge transfer (intra-CT) and intermolecular charge transfer (inter-CT) to achieve high PCEs under indoor environment in the combination of changing skeleton from symmetry to asymmetry and end group from chlorination to non-chlorination. The study reveals that, in comparison with symmetric molecule BTP-2ThCl, asymmetric structure TB-SCl possesses a smaller intra-CT resulting in higher V_OC and strengthened inter-CT for neighboring acceptors resulting in more efficient carrier collection and thus higher FF. Moreover, the non-chlorine molecule TB-S exhibits smaller intra and inter-CT leading to further promoting V_OC but smaller FF compared with TB-SCl under 1-sun illumination. When the illumination is switched to artificial light, the mitigated trap state, minimized leakage current, and suppressed non-radiative energy loss (∆E_nonrad) enable a novel acceptor TB-S yielding high-efficiency rigid PCE of 23.3 % which surpasses TB-SCl and flexible PCE of 20.02% which is one of the best PCE for flexible IOPVs. Our observation provides a new insight into molecule structure modification to promote the indoor photovoltaic performance.