Manipulation of PBDT-DTNT:PCBM photoactive layers for a stability increment by core–shell and core–mantle–shell supramolecules

Abstract

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 (J_sc), fill factor (FF), open circuit voltage (V_oc) 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.