Improved stability in P3HT:PCBM photovoltaics by incorporation of well-designed polythiophene/graphene compositions

Morphological and photovoltaic stabilities of poly(3-hexylthiophene) (P3HT):phenyl-C-61-butyric acid methyl ester (PC71BM) solar cells were investigated in pristine and modified states. To this end, four types of patterned/assembled nanostructures, namely reduced graphene oxide (rGO)-g-poly(3-dodecylthiophene)/P3HT patched-like pattern, rGO-polythiophene/P3HT/PC71BM nanofiber, rGO-g-P3HT/P3HT cake-like pattern and supra(polyaniline (PANI)-g-rGO/P3HT), were designed on the basis of rGO and various conjugated polymers. Intermediately covered rGO nanosheets by P3HT crystals (supra(PANI-g-rGO/P3HT)) performed better than sparsely (patched-like pattern) and fully (cake-like pattern) covered ones in P3HT:PC71BM solar cell systems. Supra(PANI-g-rGO/P3HT) nanohybrids largely phase-separated in active layers (root mean square = 0.88 nm) and also led to the highest performance (power conversion efficiency of 5.74%). The photovoltaic characteristics demonstrated decreasing trends during air aging for all devices, but with distinct slopes. The steepest decreasing plots were obtained for the unmodified P3HT:PC71BM devices (from 1.77% to 0.28%). The two supramolecules with the most ordered structures, that is, cake-like pattern (10.12 mA cm(-2), 51%, 0.58 V, 2.2 x 10(-6) cm(2) V-1 s(-1), 4.3 x 10(-5) cm(2) V-1 s(-1), 0.69 nm and 2.99%) and supra(PANI-g-rGO/P3HT) (12.51 mA cm(-2), 57%, 0.63 V, 1.2 x 10(-5) cm(2) V-1 s(-1), 3.4 x 10(-4) cm(2) V-1 s(-1), 0.82 nm and 4.49%), strongly retained morphological and photovoltaic stabilities in P3HT:PC71BM devices after 1 month of air aging. According to the morphological, optical, photovoltaic and electrochemical results, the supra(PANI-g-rGO/P3HT) nanohybrid was the best candidate for stabilizing P3HT:PC71BM solar cells. (c) 2020 Society of Chemical Industry