Manipulation of PBDT-DTNT:PCBM photoactive layers for a stability increment by core–shell and core–mantle–shell supramolecules†
Two types of core–shell and core–mantle–shell supramolecules were designed based on grafted-carbon nanotubes (CNTs) and poly[benzodithiophene-bis(decyltetradecyl-thien)naphthothiadiazole] (PBDT-DTNT) chains and employed in the active layers of PBDT-DTNT:phenyl-C61-butyric acid methyl ester (PC71BM) solar cells to stabilize the morphology and performance. These nano-hybrids were composed of CNT-g-poly(3-dodecylthiophene) (PDDT)/PBDT-DTNT and CNT-g-polyaniline (PANI)/PBDT-DTNT precursors, respectively. The overall diameter of the core–shell and core–mantle–shell nanostructures ranged within 85–95 and 110–120 nm, respectively. In contrast to the pure CNTs (3.55%), the pre-designed core (CNT)–shell (PBDT-DTNT) and core (CNT)–mantle (PANI)–shell (PBDT-DTNT) nanostructures considerably affected the photovoltaic characteristics and efficiencies of 4.83 and 6.71% were acquired, respectively. From the pure CNT-based photovoltaics towards the core–shell and core–mantle–shell modified systems, the slopes of decreasing curves of short circuit current density (Jsc), fill factor (FF), open circuit voltage (Voc) and power conversion efficiency (PCE) versus aging time became slower, proving higher stability in the well-functioning photovoltaic devices. The core–mantle–shell nanostructures not only largely phase separated and absorbed at more red-shifted wavelengths, but also further stabilized the device morphology and performance. Within 1 month aging, the characteristics of (9.69 mA cm−2, 52%, 0.57 V, 2.3 × 10−6 cm2 V−1 s−1, 4.8 × 10−5 cm2 V−1 s−1, 806 Ω cm2 and 2.87%) and (12.74 mA cm−2, 64%, 0.64 V, 8.4 × 10−5 cm2 V−1 s−1, 9.7 × 10−4 cm2 V−1 s−1, 543 Ω cm2 and 5.21%) were retained for the core–shell and core–mantle–shell based systems, respectively.