Photovoltaic Performances of Fused Ring Acceptors with Isomerized Ladder-Type Dipyran Cores

Abstract

We precisely design and synthesize two A−π–D−π–A type dipyran-cored nonfullerene acceptors (NFAs) Ph-DTDP o -OT and Ph-DTDP i -OT with oxygen atoms at the outer and inner positions, respectively. 3-Hexyloxythiophene is used as the π-spacer to expand the effective conjugation length of the acceptors. These two NFAs possess similar optical band gaps and energy levels. However, the position of the oxygen atom at the dipyran core can markedly influence the molecular packing and aggregation behavior of the resulted acceptors. Ph-DTDP o -OT with a strong intermolecular affinity tends to form larger aggregates blending with PBDB-T, leading to a lower photovoltaic performance; Ph-DTDP i -OT presents good miscibility with PBDB-T and the blend films preferentially adopt a face-on orientation. Ph-DTDP i -OT-based devices display high and balanced hole and electron mobilities, leading to an optimal power conversion efficiency of 11.38%, which is much higher than those of Ph-DTDP o -OT-based ones (7.60%). Moreover, Ph-DTDP i -OT-based devices also exhibit a lower nonradiative recombination voltage loss of 0.268 eV. Our work demonstrates that the π-spacer and chemical structure of the core unit can greatly influence the molecular packing and the morphology of blend films, which are critical to the photovoltaic performance of devices.

Isomerization Strategy of Nonfullerene Small‐Molecule Acceptors for Organic Solar Cells

“…Also, Bo and co-workers designed two dipyran-cored SMAs (Ph-DTDP o -OT and Ph-DTDP i -OT) with oxygen atoms at the outer and inner positions, respectively. [119] The pristine film of Ph-DTDP o -OT and Ph-DTDP i -OT exhibited similar edge-on packing. However, due to the strong intermolecular aggregation of Ph-DTDP o -OT, the disfavored edge-on packing style is still maintained in PBDB-T:Ph-DTDP o -OT-based blend film, accounting for its relatively low efficiency (7.60%).…”

Molecular Origin of Carbon–Oxygen‐Bridge Isomerization Induced Reverse Aggregation Ability in Acceptor–Donor–Acceptor Electron Acceptors for Organic Solar Cells

“…From the previous reports, [ 17,22,33 ] it can be seen that the isomerization of the oxygen position can give rise to a large difference in global morphology and device performance. In particular, after side‐chain branching and end‐group fluorination, the relative aggregation ability between the CO‐bridge isomers turns to be reverse: TPTC (inner oxygen) > TPTIC (outer oxygen) versus NBDTP‐Fin (inner oxygen) < NBDTP‐Fout (outer oxygen).…”

Molecular optimization of incorporating pyran fused acceptor–donor–acceptor type acceptors enables over 15% efficiency in organic solar cells

“…Pyran fused rings have been explored as distinctive blocks to construct a class of highly efficient NFAs. 11,37,46–58 Recently, our group developed an encouraging NFA, FO-2F , 45 featuring an easily synthesized pyran fused ring as the main building kernel. Note that FO-2F -based OSCs have afforded excellent PCEs, rendering them one of the most promising candidates for economically feasible OSC molecules.…”