Theoretical Insight into the Internal Quantum Efficiencies of Polymer/C${}_{60}$ and Polymer/SWNT Photovoltaic Devices

Abstract

The internal quantum efficiency (IQE) of an organic photovoltaic device (OPV) is proportional to the number of free charge carriers generated and their conductivity, per absorbed photon. However, both the IQE and the quantities that determine it, for example, electron-hole binding, charge separation, electron-hole recombination, and conductivity, can only be inferred indirectly from experiments. Using density functional theory, we calculate the excited-state formation energy, charge transfer, and zero-bias conductance in the singlet ground state and triplet excited state across polymer/fullerene and polymer/single walled carbon nanotube (SWNT) OPV donor/acceptor bulk heterojunctions. Specifically, we compare polythiophene (PT) and poly(3-methylthiophene-2,5-diyl) (P3MT) as donors and C${}_{60}$ chains with (6,4), (6,5), and (10,5) SWNTs as acceptors. We find the conductivity increases substantially for both the excited triplet relative to the singlet ground state and for PT compared with P3MT due to the increased charge transfer and the resulting improvement in donor/acceptor level alignment. Similarly, the (6,4) SWNT, with a larger SWNT band gap and greater conductivity than fullerenes, provides the highest conductivities of 5 and 9\% of the theoretical maximum for electron and hole carriers, respectively. This work has important implications for both the optimization of polymer/SWNT bulk heterojunctions and the design of new OPV bulk heterojunctions in silico.

7 pages, 3 figures, 3 tables

References in corpus (13)

• Exciton binding energies in carbon nanotubes from two-photon photoluminescence
• Localized atomic basis set in the projector augmented wave method
• Tight--binding description of the quasiparticle dispersion of graphite and few--layer graphene
• Benchmark density functional theory calculations for nano-scale conductance
• Quasiparticle level alignment for photocatalytic interfaces
• Comparing quasiparticle H${}_2$O level alignment on anatase and rutile TiO${}_2$
• Plasmon excitations on a single-wall carbon nanotube by external charges: two-dimensional, two-fluid hydrodynamic model
• Theoretical electron energy loss spectroscopy of isolated graphene
• Quasiparticle interfacial level alignment of highly hybridized frontier levels: H${}_2$O on TiO${}_2$(110)
• Using $G_0{W}_0$ Level Alignment to Identify Catechol's Structure on TiO${}_2$(110)
• Photoinduced Absorption within Single-Walled Carbon Nanotube Systems
• Using surface plasmonics to turn on fullerene's dark excitons
• PFO-BPy Solubilizers for SWNTs: Modelling of Polymers from Oligomers

Cited by in corpus (1)

• Optical Absorption and Energy Loss Spectroscopy of Single-Walled Carbon Nanotubes