Enhanced Uniformity and Area Scaling in Carbon Nanotube–Fullerene Bulk‐Heterojunction Solar Cells Enabled by Solvent Additives

Single‐walled carbon nanotube (SWCNT) fullerene solar cells have recently attracted attention due to their low‐cost processing, high environmental stability, and near‐infrared absorption. While SWCNT–fullerene bulk‐heterojunction photovoltaics employing an inverted architecture and polychiral SWCNTs have achieved efficiencies exceeding 3% over device areas of ≈1 mm 2 , large‐area SWCNT solar cells have not yet been demonstrated. In particular, with increasing device area, spatial inhomogeneities in the SWCNT film have limited overall device performance. Here, 1,8‐diiodooctane (DIO) is utilized as a solvent additive to reduce fullerene domain size and to improve SWCNT–fullerene bulk‐heterojunction morphology. Under optimized conditions, DIO elucidates the influence of SWCNT chiral distribution on overall device performance, revealing a tradeoff between short‐circuit current density and fill factor as a function of the chirality distribution present. The combination of SWCNT chirality distribution engineering and improved spatial homogeneity via solvent additives enables area‐scaling of SWCNT–fullerene solar cells with performance comparable to small‐area cells.