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Title: Critical role of domain crystallinity, domain purity and domain interface sharpness for reduced bimolecular recombination in polymer solar cells

Journal Article · · Nano Energy
 [1];  [2];  [1];  [1];  [1];  [1];  [1]
  1. South Dakota State Univ., Brookings, SD (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)

In this study, inverted bulk heterojunction solar cells were fabricated using poly(3-hexylthiophene) (P3HT) blended with two different fullerene derivatives namely phenyl-C61-butyric acid methyl ester (PC60BM) and indene-C60 bis-adduct (IC60BA). The effects of annealing temperatures on the morphology, optical and structural properties were studied and correlated to differences in photovoltaic device performance. It was observed that annealing temperature significantly improved the performance of P3HT:IC60BA solar cells while P3HT:PC60BM cells showed relatively less improvement. The performance improvement is attributed to the extent of fullerene mixing with polymer domains. Energy filtered transmission electron microscopy (EFTEM) and x-ray diffraction (XRD) results showed that ICBA mixes with disordered P3HT much more readily than PC60BM which leads to lower short circuit current density and fill factor for P3HT:IC60BA cells annealed below 120°C. Annealing above 120°C improves the crystallinity of P3HT in case of P3HT:IC60BA whereas in P3HT:PC60BM films, annealing above 80°C leads to negligible change in crystallinity. Crystallization of P3HT also leads to higher domain purity as seen EFTEM. Further it is seen that cells processed with additive nitrobenzene (NB) showed enhanced short circuit current density and power conversion efficiency regardless of the fullerene derivative used. Addition of NB led to nanoscale phase separation between purer polymer and fullerene domains. Kelvin probe force microscopy (KPFM) images showed that enhanced domain purity in additive casted films led to a sharper interface between polymer and fullerene. Lastly, enhanced domain purity and interfacial sharpness led to lower bimolecular recombination and higher mobility and charge carrier lifetime in NB modified devices.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1265400
Alternate ID(s):
OSTI ID: 1252083
Journal Information:
Nano Energy, Vol. 12; ISSN 2211-2855
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 38 works
Citation information provided by
Web of Science

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Cited By (8)

Kelvin Probe Force Microscopy Characterization of Organic and Hybrid Perovskite Solar Cells book January 2018
An oligothiophene chromophore with a macrocyclic side chain: synthesis, morphology, charge transport, and photovoltaic performance journal January 2016
Impact of the solubility of organic semiconductors for solution-processable electronics on the structure formation: a real-time study of morphology and electrical properties journal January 2018
Critical Role of Polymer Aggregation and Miscibility in Nonfullerene‐Based Organic Photovoltaics journal January 2020
Modulation of molecular orientation enabling high photovoltaic performance of block copolymer nanostructures journal January 2019
Characterization of organic solar cells using semiconducting polymers with different bandgaps journal July 2019
Improving Photovoltaic Properties of P3HT:IC60BA through the Incorporation of Small Molecules journal January 2018
Non-halogenated diphenyl-chalcogenide solvent processing additives for high-performance polymer bulk-heterojunction solar cells journal January 2018