Bulk Heterojunction Solar Cells from Poly(3-butylthiophene)/Fullerene Blends: In Situ Self-Assembly of Nanowires, Morphology, Charge Transport, and Photovoltaic Properties

Abstract

Bulk heterojunction solar cells based on blends of regioregular poly(3-butylthiophene) (P3BT) and phenyl-C61-butyric acid methyl ester (PC61BM) were created by in situ self-assembly of P3BT nanowires and the morphology and photovoltaic properties were investigated as a function of the blend composition. Transmission electron microscopy imaging of the blends revealed an interconnected network of P3BT nanowires of 11−15 nm width and 5−10 μm length and an amorphous continuous PC61BM phase. The photocurrent density, fill factor, and power conversion efficiency of the P3BT nanowire/PC61BM solar cells varied significantly with the blend composition whereas the open circuit voltage was relatively constant (570−610 mV). A maximum power conversion efficiency of 2.52% was achieved at a 1:0.5 (wt:wt) P3BT:PC61BM blend ratio. The hole mobilities in the P3BT nanowire/PC61BM blends measured by space-charge limited current and field-effect transistors were on the order of 1 × 10−3 cm2/V s and a linear dependence of current density on light intensity was observed in the blend solar cells. These results demonstrate that in situ self-assembly of polymer semiconductor nanowires as active blend component is a promising approach to the rational control of the film morphology of bulk heterojunction solar cells.

Poly(3‐hexylthiophene)‐b‐poly(3‐cyclohexylthiophene): Synthesis, microphase separation, thin film transistors, and photovoltaic applications

“…5(A)], whereas HcH77 appears as polymer nanowires with an average width of 12.5 6 0.9 nm and aspect ratios of 50-120 in Figure 5(B). This is similar to the parent homopolymer P3HT, 49 other poly (3-alkylthiophene)s, [49][50][51] and poly(3-butylthiophene)-b-poly (3-octylthiophene), 41 crystalline polymer chains, which also undergo self-organization into nanowires from solution governed by strong p-p stacking interactions.…”

Direct Evaluation of Intrinsic Optoelectronic Performance of Organic Photovoltaic Cells with Minimizing Impurity and Degradation Effects

“…[ 12 ] We prepared P3HT:PCBM blend fi lms with changing the mixing ratio (1:0 to 0:1, w/w) from o -dichlorobenzene ( o DCB) solutions by drop-casting onto quartz plates. The fi lm thicknesses were more than 1 μ m to absorb most of the incident photons, so that the change of photoabsorbance by the blend ratio could be ignored.…”

Nanoscale assembly into extended and continuous structures and hybrid materials

“…25 The high hole mobility of P3HT nanowires is attractive for organic PVs, especially when combined with electron carriers, such as fullerenes. PV devices having active layers fabricated from solutionassembled poly(3-alkyl thiophene) nanowires display power conversion efficiency (PCE) values comparable with optimized devices that require annealing of P3HT/fullerene films; 15,19,26,27 for example, blending phenyl C 61 Àbutyric acid methyl ester (PC 60 BM) with P3HT fibrils gave devices with a 3.9% PCE, significantly higher than that obtained for thin films of noncrystallized P3HT and PC 60 BM (1.1%), and on par with annealed thin films (3.7%). 28 Active layers prepared by deposition of solution-prepared fibrils do not suffer from the vertical phase separation of the polymer and fullerene components, as observed during thermal annealing of conventional thin films.…”