The role of hydrogen bonding in bulk-heterojunction (BHJ) solar cells: A review

Bulk-heterojunction (BHJ) solar cells have attracted tremendous attention in the recent years due to their potential to provide an earth-abundant and low cost solution to solar energy conversion. Unlike inorganic solar cells, BHJ solar cells use small molecular or polymeric light absorbers which can be delicately designed and assembled. With the aim of facilitating light absorption and improving morphology for efficient charge separation and transfer, hydrogen-bonding (H-bonding) has been employed in BHJ solar cells due to its relatively strong non-covalent interactions, highly directional and specific characteristics. The current review aims to summarize H-bonding in small molecule and polymer based donor materials as well as acceptor materials in BHJ solar cells. Emphasis will be placed on the molecular design of incorporating H-bonding in the donor and acceptor materials. The morphology optimization and power conversion efficiency (PCE) improvement in the presence of H-bonding will be the central topics of this review.