The effect of three-dimensional morphology on the efficiency of hybrid polymer solar cells

Abstract

The efficiency of polymer solar cells critically depends on the intimacy of mixing of the donor and acceptor semiconductors used in these devices to create charges and on the presence of unhindered percolation pathways in the individual components to transport holes and electrons. The visualization of these bulk heterojunction morphologies in three dimensions has been challenging and has hampered progress in this area. Here, we spatially resolve the morphology of 2%-efficient hybrid solar cells consisting of poly(3-hexylthiophene) as the donor and ZnO as the acceptor in the nanometre range by electron tomography. The morphology is statistically analysed for spherical contact distance and percolation pathways. Together with solving the three-dimensional exciton-diffusion equation, a consistent and quantitative correlation between solar-cell performance, photophysical data and the three-dimensional morphology has been obtained for devices with different layer thicknesses that enables differentiating between generation and transport as limiting factors to performance.

Role of Structural Order and Excess Energy on Ultrafast Free Charge Generation in Hybrid Polythiophene/Si Photovoltaics Probed in Real Time by Near-Infrared Broadband Transient Absorption

“…25, 49,50 The polaron absorption spectrum, that we obtain in the P3HT films (Figure 3c), closely matches the subgap polaron absorption bands obtained by CW photoinduced absorption (PA) measurements as reported in recent publications. 7,11,25,51,52 Therefore, we use our measured polaron absorption spectra for the individual P3HT types for comparison with the transient absorption spectra throughout the whole work.…”

In situ syntheses of semiconducting nanoparticles in conjugated polymer matrices and their application in photovoltaics.

“…They studied charge [29] or zinc oxide [30], medium bandgap materials like cadmium sulfide [31], selenide [8,32,33] or telluride [34], copper indium sulfide [35] and selenide [36], as well as low band gap materials like lead sulfide [6], or selenide [37]. Recently, also other abundant and non-toxic materials like SnS 2 [38], FeS 2 [39] or Bi 2 S 3 [40] as well as silicon nanoparticles [41] have been researched concerning the incorporation in hybrid solar cells.…”

Oligo- and Polythiophene/ZnO Hybrid Nanowire Solar Cells

“…ZnO nanowires are an example of this class of materials that have been used for hybrid solar cells. [8][9][10]14,16 Poly(3-hexylthiophene) (P3HT)/ZnO nanowire composite solar cells are benchmark systems that have attained power conversion efficiencies ranging from 0.02 to 2%. 9,16,17 In spite of the vast efforts in this area of research, solar cells based on hybrid composites have yielded efficiencies only close to those of organic bilayer devices and significantly less than organic bulk heterojunction solar cells.…”