Fine-Tuning the Dipole Moment of Asymmetric Non-Fullerene Acceptors Enabling Efficient and Stable Organic Solar Cells

Abstract

Modifying molecular conjugation has been demonstrated as an effective strategy to enhance the photovoltaic performance of the non-fullerene small molecule acceptors (SMAs), which would regulate the molecular packing and nanoscale morphology in the active layer of organic solar cells (OSCs). Here, two novel SMAs PTIC-4Cl and PT2IC-4Cl are designed and synthesized by expanding the core unit of TB-4Cl in one or two directions. The effects of how to expand the conjugation length on the absorption property, energy levels, dipole moment, and solubility are studied via theoretical calculation and experiments. Compared to PT2IC-4Cl, PTIC-4Cl with a more asymmetric structure exhibits the larger dipole moment and enhanced intermolecular packing. The PTIC-4Cl-based OSCs exhibit a favorable morphology and balanced charge transport, thereby leading to the highest power conversion efficiencies. In addition, PTIC-4Cl-based devices show outstanding thermal and air stability. These results reveal that fine-tuning the dipole moment via rationally expanding the conjugation in asymmetric A-D1A′D2-A-type non-fullerene acceptors is critical to achieve high-performance OSCs.

Single‐Junction Organic Solar Cells with 19.17% Efficiency Enabled by Introducing One Asymmetric Guest Acceptor

“…More recently, Sun and co-workers developed an NFA named L8-BO by substituting the beta position of the thiophene unit on the Y6-central core with branched alkyl chains, [5] which exhibits upshifted energy levels and improved molecular packing, thus yielding a PCE of 18.32% with a FF of 81.5% in PM6:L8-BO OSCs. Apart from the terminal group and side-chain engineering, the asymmetric designs (in endgroups, [34,35] side-chains, [36] skeleton, [37][38][39] etc.) enable the photovoltaic systems to get further a step in device performance owing to the fine-tuning of photophysical and electrochemical properties, molecular orientation and stacking pattern, etc.…”

Exploiting Novel Unfused‐Ring Acceptor for Efficient Organic Solar Cells with Record Open‐Circuit Voltage and Fill Factor

“…The crystallinity and molecular stacking behaviors of the pure and blend films were further studied via grazing‐incidence wide angle X‐ray scattering (GIWAXS) analysis [45–48] . The 2D GIWAXS patterns and 1D line cuts of the neat and blend films are shown in Figure 7a–e, and the related parameters are summarized in Table S5.…”

“…The crystallinity and molecular stacking behaviors of the pure and blend films were further studied via grazing-incidence wide angle X-ray scattering (GIWAXS) analysis. [45][46][47][48] The 2D GIWAXS patterns and 1D line cuts of the neat and blend films are shown in Figure 7a-e, and the related parameters are summarized in Table S5. Both BTCD-IC and BTCD-2FIC adopted face-on orientation because the introduction of DTBT core is more conducive to the face-on orientation of molecules.…”

Heating‐induced aggregation control for efficient sequential‐cast organic solar cells

“…[10][11][12][13] The molecular ordering and aggregation of donors and acceptors within the photoactive layer are critical for light absorption and photon-to-electricity conversion process. [14][15][16][17][18] Besides chemical approaches to modulate the molecular structural of NFAs, [19,20] numerous physical approaches including liquid and solid additives, [21][22][23] thermal annealing, solvent vapor annealing, [24] solvent mixture, [25] and hot-substrate (HS) casting [26][27][28] have all been applied in impacting the molecular ordering and aggregation behavior of NFAs.…”