• Energy Research

Quantitative relationship between the protective factor (δ) and PCE of stacked structures of OSC with a record PCE of 17.52% is proposed to understand the mechanism and provide a guideline for solvent choices of eco-friendly solvent protection method.

The investigation of the surface energy parameters of photovoltaic materials highlights the wetting coefficient as a dominant dynamic for spontaneous Voc gain.

A combination of high open-circuit voltage (Voc) and short-circuit current density (Jsc) typically creates effective organic solar cells (OSCs). Y5, a member of the Y-series acceptors, can achieve high Voc of 0.94 V with PM6 but low Jsc of 12.8 mA cm-2. To maintain the high Voc while increasing the Jsc of devices, we developed a new nonfullerene acceptor, namely, BTP-C2C4-N, by extending the conjugation of a Y5 molecule with a naphthalene-based end acceptor. In comparison with Y5-based devices, PM6:BTP-C2C4-N-based devices exhibited significantly higher Jsc of 18.2 mA cm-2 followed by a high Voc. To further increase the photovoltaic properties of BTP-C2C4-N analogues, BTP-C4C6-N and BTP-C6C8-N molecules with better processability and film morphology are obtained by adjusting the alkyl branched chain length. The optimized OSCs based on BTP-C4C6-N with a moderate alkyl branched chain length exhibited the best PCE of 12.4% with a high Voc of 0.94 V and Jsc of 20.7 mA cm-2. Notably, the devices achieved a low energy loss of 0.49 eV (0.51 eV for Y5 system) accompanied by a small nonradiative energy loss. The results indicate that nonfullerene acceptors with extended terminal motifs and optimized branched chain lengths can effectively enhance the performance of OSCs and reduce energy loss.

By constructing a ternary cell with a B1:BO-2Cl:BO-4Cl donor:acceptors combination, an outstanding power conversion efficiency (PCE) of 17.0% (certified to be 16.9%) has been realized for all-small-molecule organic solar cells (ASM-OSCs).

A series of polymer acceptors have been synthesized. The optical and electronic properties of the copolymers can be well-tuned via a random copolymerization strategy. The best-performing PY-82-based binary device produces a record-high efficiency of 17.15%.

Two isomeric A–DA′D–A type SMAs o-TEH and m-TEH were designed and synthesized, and the PCE of the OSC based on PBQ6:m-TEH reached 18.51%.