Design of organic small molecules for photovoltaic application with high open-circuit voltage (Voc)

Open-circuit voltage (V-oc), as a key parameter, plays an important role in determining power conversion efficiency (PCE) of organic solar cells (OSCs). With the rapid development in OSCs based on small molecules, more and more attention has been paid to fabricate photovoltaic devices with high V-oc values by designing novel small molecule materials, which has pushed the highest V-oc values for single-junction OSCs based on small molecules as donors or acceptors to be 1.12 V and 1.36 V, respectively. In this review, recent advances with respect to photovoltaic materials applied in OSCs featuring high V-oc values will be summarized from two aspects: small molecule donors and small molecule acceptors. Moreover, we will systematically discuss the relationship between molecular structures of small molecule materials and V-oc values for OSCs, which will provide a guideline on the design of organic small molecule materials for obtaining photovoltaic devices with high V-oc values.