Efficient ternary all small molecule organic photovoltaics with NC70BA as third component materials

Abstract

Inverted small molecule organic photovoltaics (SMPVs) were fabricated with BTR as a donor, the narrow band gap material Y11 as an acceptor and NC70BA fullerene derivatives with a broad band gap as the third component materials. When 20 wt% Y11 was replaced by NC70BA, a higher PCE of 13.92% was achieved, which is attributed to simultaneous enhancement of the JSC of 22.16 mA cm−2, the VOC of 0.905 V and the FF of 69.4%. The hollow spherical structure of NC70BA may lead to the connection of Y11 and BTR molecules to form more continuous electron transport channels. Shallow lowest unoccupied molecular orbital (LUMO) energy levels form a cascade of LUMO energy levels among the used materials. In addition, the molecular arrangement and crystallinity in the photoactive layer can be markedly adjusted by incorporating NC70BA into BTR:Y11 binary films. The well-optimized phase separation and molecular arrangement in ternary photoactive layers can well support an enhanced JSC and FF for ternary SMPVs. Thus, the photovoltaic performance of SMPVs can be well improved by employing a ternary strategy with NC70BA as the third component materials.