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 mm², 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. Solvent additives enable large-area carbon nanotube solar cells by reducing spatial inhomogeneities within the carbon nanotube-fullerene active layer. These additives also reveal the impact of carbon nanotube chiral distribution on performance and enable the fabrication of large-area carbon nanotube solar cells with power conversion efficiencies comparable to small-area cells.