Unraveling the Instability Issues in P3HT:PCBM Solar Cells by Graphene/Carbon Quantum Dots and Host Polymer Chain/Fiber Arrangements

Abstract

Different quantum dot (QD)-based supramolecules subsuming crab-shape poly(3-hexylthiophene) (P3HT) short chain/graphene quantum dot (GQD) and half crab-shape P3HT short chain/carbon quantum dot (CQD), patterned P3HT/GQD and P3HT/CQD long chain, fibrillar P3HT/GQD, and fibrillar P3HT/CQD nanostructures were fabricated to stabilize P3HT:[6,6]phenyl C71 butyric acid methyl ester (PC71BM) solar cells during air aging. The P3HT crystals were composed of face-on (( 100) and ( 002) prisms) and edge-on (( 020) and ( 002) growth planes) oriented chains with distinct qualities of crystallinity. Within 1.5 months of aging in 36% humidity at 34°C, P3HT:PC71BM photovoltaics and some of their modified states were no longer applicable and went down to 0% efficacy. Only the photoactive layers modified by the fibrillar P3HT/CQD (1.74% and 790 Ω cm 2 ), crab-shape P3HT/GQD (0.45% and 896 Ω cm 2 ), patterned P3HT/GQD (0.29% and 918 Ω cm 2 ) and fibrillar P3HT/GQD (3.39% and 670 Ω cm 2 ) supramolecules reflected non-zero performances. The decreasing slopes of photovoltaic characteristics versus the aging time were the slowest for the fibrillar P3HT/GQD-based solar cells, and performances of 6.50% (14.05 mA cm −2 , 66.11%, and 0.70 V), 5.70% (13.34 mA cm −2 , 62.79%, and 0.68 V), 4.53% (12.51 mA cm −2 , 56.60%, and 0.64 V) and 3.39% (11.67 mA cm −2 , 51.83%, and 0.56 V) were recorded during 0, 30, 60 and 90 days of air aging, respectively. Single crystallinity of P3HT fibrils, on one hand, and flat structure of GQDs, on the other hand, were the origins of this phenomenon. More stabilized photovoltaics depicted longer half-life with respect to less stabilized ones, e.g., 93 versus 19 days for P3HT:PC71BM:fibrillar P3HT/GQD and P3HT:PC71BM systems, respectively.