Distorted Asymmetric Cubic Nanostructure of Soluble Fullerene Crystals in Efficient Polymer:Fullerene Solar Cells

Abstract

We found that 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C(61) (PCBM) molecules make a distorted asymmetric body-centered cubic crystal nanostructure in the bulk heterojunction films of reigoregular poly(3-hexylthiophene) and PCBM. The wider angle of distortion in the PCBM nanocrystals was approximately 96 degrees , which can be assigned to the influence of the attached side group to the fullerene ball of PCBM to bestow solubility. Atom concentration analysis showed that after thermal annealing the PCBM nanocrystals do preferentially distribute above the layer of P3HT nanocrystals inside devices.

Initial Performance Changes of Polymer/Fullerene Solar Cells by Short‐Time Exposure to Simulated Solar Light

“…This result supports the notion that continuous illumination with simulated solar light increases the temperature inside the sample holder (sealed tightly), leading to a minimal phase tran- www.chemsuschem.org sition at the surface of the blend film. In the case of metastable domains (phases) caused inevitably by thermal annealing, as often observed from the P3HT:PCBM blend films, [28,29,31] their phase transition could be easily accelerated by even small (thermal) impacts. Hence, we consider that the surface of the P3HT:PCBM blend film might be affected by heating effects during 11 h exposure.…”

“…In contrast, the J-V curves of C-2 devices showed a relatively larger change, that is, a lowered V oc , after 11 h exposure ( Figure 2 b and d), which may be attributed to the imperfect setting of the blend morphology in comparison with the C-1 devices. [28,29] In Figure 3, detailed trends of cell performances as a function of exposure time are given. For C-1 devices (Figure 3 a), the J sc value initially increased as the exposure time increased up to 2 h, but then showed a gradual decay with up-anddown fluctuations.…”

“…In other words, after 11 h of exposure the fraction of PCBM at the surface of the blend film might be increased marginally, as observed in the case of over-annealing. [28,31] To understand the change in the surface composition of the blend film (annealed at 140 8C for 2 h) after 11 h exposure, AFM measurements were performed on almost the same regions of the blend film surface: the measured surface of the blend film sample was marked before exposure, and the same part was then measured again after exposure. As shown in Figure 5, we attempted to measure the exact same region but the position was slightly shifted (see positions A and B in Figure 5 c and d).…”

Morphology Development in Amorphous Polymer:Fullerene Photovoltaic Blend Films During Solution Casting

“…The presence of a broad symmetric ring at this Q-value indicates a random orientation of small fullerene domains within the fi lm. [ 33 ] From Figure 4 (a) it is apparent that X-ray scatter from PC 70 BM molecules is already relatively pronounced by the time at which X-ray scatter from the PCDTBT-rich phase of the fi lm is fi rst resolved. This is clarifi ed in Figure 5 , where we detail X-ray scatter over the Q-range 0.1-0.45 Å −1 from the sample over the time range 180-300 s after solution casting.…”

Traceable atomic force microscopy of high-quality solvent-free crystals of [6,6]-phenyl-C61-butyric acid methyl ester

“…5,6 Devices based on poly(3-hexylthiophene-2,5-diyl) (P3HT) and PCBM blends display better performance following thermal annealing that alters the fraction of amorphous and microcrystalline PCBM domains, 7,8 with the formation of PCBM nano-crystalline domains that are crucial for high power conversion efficiencies (PCE). 9,10 One of the issues that have hampered progress so far is that the crystal structure of PCBM turns out to be strongly dependent on the solvent in which the crystals are grown and which remain in the crystals themselves as an inclusion. Recently, we have proposed a solution-based procedure to obtain large, solvent-free, high-quality PCBM crystals.…”