TY - JOUR
T1 - The impact of selective solvents on the evolution of structure and function in solvent annealed organic photovoltaics
AU - Hu, Sheng
AU - Dyck, Ondrej
AU - Chen, Huipeng
AU - Hsiao, Yu Che
AU - Hu, Bin
AU - Duscher, Gerd
AU - Dadmun, Mark
AU - Khomami, Bamin
PY - 2014
Y1 - 2014
N2 - This study examines the development of structure and performance in an organic photovoltaic (OPV) thin film comprised of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Specifically, the influence of P3HT and PCBM solubility in the solvents utilized for vapor annealing on the morphological properties and OPV performance of the resultant active layer is examined. The evolution of P3HT crystallinity as well as the growth of PCBM aggregates in the solvent annealed thin films were examined by Grazing Incidence Wide Angle X-ray Scattering (GIWAXS), Atomic Force Microscopy (AFM), and Energy Filtered Transmission Electron Microscopy (EFTEM). It is shown that P3HT crystallinity increases initially, then decreases with time for solvents that have a finite P3HT solubility. Alternatively, PCBM aggregates grow continuously with SVA, but are modulated by the PCBM solubility. High P3HT crystallinity and moderate PCBM phase separation correlates to improved power conversion efficiency (PCE). Hence, the relative P3HT and PCBM solubility plays a crucial role in choosing the best SVA time of different annealing solvents. Specifically, for samples annealed using solvents that prefer P3HT, PCE benefits from further SVA after the peak P3HT crystallinity time, which is ascribed to additional PCBM phase separation. On the other hand, solvents that prefer PCBM induce excess PCBM phase separation at longer SVA times, which limits exciton dissociation and PCE. EFTEM cross section images indicate that PCBM is distributed toward the bottom of the film, whereas SVA in a solvent with high PCBM solubility may induce PCBM to segregate towards the air surface, which benefits charge transport processes by preventing electron-hole recombination. This journal is
AB - This study examines the development of structure and performance in an organic photovoltaic (OPV) thin film comprised of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Specifically, the influence of P3HT and PCBM solubility in the solvents utilized for vapor annealing on the morphological properties and OPV performance of the resultant active layer is examined. The evolution of P3HT crystallinity as well as the growth of PCBM aggregates in the solvent annealed thin films were examined by Grazing Incidence Wide Angle X-ray Scattering (GIWAXS), Atomic Force Microscopy (AFM), and Energy Filtered Transmission Electron Microscopy (EFTEM). It is shown that P3HT crystallinity increases initially, then decreases with time for solvents that have a finite P3HT solubility. Alternatively, PCBM aggregates grow continuously with SVA, but are modulated by the PCBM solubility. High P3HT crystallinity and moderate PCBM phase separation correlates to improved power conversion efficiency (PCE). Hence, the relative P3HT and PCBM solubility plays a crucial role in choosing the best SVA time of different annealing solvents. Specifically, for samples annealed using solvents that prefer P3HT, PCE benefits from further SVA after the peak P3HT crystallinity time, which is ascribed to additional PCBM phase separation. On the other hand, solvents that prefer PCBM induce excess PCBM phase separation at longer SVA times, which limits exciton dissociation and PCE. EFTEM cross section images indicate that PCBM is distributed toward the bottom of the film, whereas SVA in a solvent with high PCBM solubility may induce PCBM to segregate towards the air surface, which benefits charge transport processes by preventing electron-hole recombination. This journal is
UR - http://www.scopus.com/inward/record.url?scp=84903849179&partnerID=8YFLogxK
U2 - 10.1039/c4ra02257b
DO - 10.1039/c4ra02257b
M3 - Article
AN - SCOPUS:84903849179
SN - 2046-2069
VL - 4
SP - 27931
EP - 27938
JO - RSC Advances
JF - RSC Advances
IS - 53
ER -