Materials science

Optoelectronics

Engineering

Composite material

Physics

Nanotechnology

Polymer chemistry

Crystallization

Energy conversion efficiency

Organic solar cell

Oligomer

Acceptor

Thermal stability

Polymer solar cell

Active layer

Condensed matter physics

Photoactive layer

Chemical engineering

Layer (electronics)

Polymer

Thin-film transistor

Nature Energy

The power conversion efficiencies of organic solar cells (OSCs) have reached over 19%. However, the combination of high efficiency and long-term stability is still a major conundrum of commercialization. Here a Y6-analogue and a 2,2′-bithiophene unit are utilized to construct a series of oligomer acceptors to investigate the effect of molecular size and packing properties on photovoltaic performance. By altering the molecular chain length, we modify the thermal properties, crystallization behaviours and molecular packing and achieve an optimal microstructure and a more stable morphology in blend films. A combination of efficiencies over 15% and an extrapolated T80 lifetime over 25,000 h, which equates to an average lifetime exceeding 16 years in Guangzhou, is achieved for binary OSCs based on an oligomer acceptor. This work emphasizes the importance of oligomeric strategy in tuning molecular packing behaviours and blend morphology, leading to development of novel non-fullerene acceptors for stable and efficient OSCs. Achieving both high efficiency and stability in organic solar cells is challenging. Now, Liang et al. show that oligomer acceptors improve the molecular packing and morphology of the active layer, affording a 15% efficiency and enhanced stability.

Organic solar cells using oligomer acceptors for improved stability and efficiency