Tackling stability of polymer solar cells with thermocleavable side chains: materials and devices*

Record high efficiency for polymer solar cells (PSCs) has now approached 20%; however, there are a few roadblocks that significantly hamper its commercialization, in particular, stability. Increasing the glass transition temperature (Tg) of the materials used in PSCs can largely mitigate the thermal instability, yet most conjugated polymers used in high-efficiency PSCs only show low Tg values, mainly due the long and bulky side chains needed for solution processing of such polymers. Thermally removing cleavable side chains is an effective approach to re-gain the high Tg of CPs after the film formation, thereby achieving higher stability. This talk will focus on our recent efforts in applying thermocleavable side chains to achieve high stability of polymer solar cells, from archetypical polythiophenes to state-of-the-art donor-acceptor type copolymers.