Annealing (glass)

Polymer solar cell

Engineering

Polymer chemistry

Materials science

Side chain

Solvent

Chemical engineering

Polymer

Organic chemistry

Composite material

Chemistry

Energy conversion efficiency

Crystallinity

Optoelectronics

Macromolecules

In this work, the impact of temperature-dependent aggregation behaviors in benzodithiophene (BDT)-based polymer donors (PDs) on the electrical, morphological, and photovoltaic performances of all-polymer solar cells (all-PSCs) is investigated. Two PDs, PBDB-T and PBDB-Bz, with thienyl or benzothienyl side chains and identical backbones are prepared. In contrast to PBDB-T, PBDB-Bz with bulkier side chains exhibits strong aggregation behavior in solution independent of temperatures between 20 and 100 °C. Notably, PBDB-Bz-based all-PSCs show a power conversion efficiency (PCE) of over 9% without any solvent additives (SAs) or thermal annealing (TA), whereas these treatments are inevitable in optimizing the PCE of PBDB-T-based all-PSCs. Furthermore, high PCEs for the PBDB-Bz-based devices are maintained, irrespective of their processing temperature (Tproc). However, the PCEs of PBDB-T-based devices are strongly dependent on their SA, TA, and Tproc conditions. This phenomenon is due to the robust nature of the domain crystallinity and blend morphology of PBDB-Bz blends at different Tprocs, resulting in Tproc-tolerant charge mobilities and PCE values. Thus, the development of PDs with temperature-insensitive, strong aggregation behavior is crucial in producing reproducible, Tproc-tolerant, and additive-free high-performance all-PSC devices.

Polymer Donors with Temperature-Insensitive, Strong Aggregation Properties Enabling Additive-Free, Processing Temperature-Tolerant High-Performance All-Polymer Solar Cells