P3HT/PCBM

Dang, M. T. Hirsch, L. Wantz, G., P3ht Pcbm, best seller in polymer photovoltaic research. Adv. Mater. 2011, 23, 3597-3602. 

Liu Z, He D, Wang Y et al (2010) Graphene doping of P3HT PCBM photovoltaic devices. Synth Met 160 1036-1039... 

Fig. 11 Adapted Onsager-Braun model for photocurrent analysis applied to P3HT PCBM. Reprinted figure with permission from [150]. Copyright 2010 by the American Physical Society...

A number of approaches are being pursued to modify the electrodes in organic solar cells in order to improve conductivity, selectivity, stability or cost. These include new electrode materials, changes in device processing and additional electrode sub-layers. Most studies have been carried out using the leading material combination, P3HT PCBM, as the active layer. 

Structural instability due to phase segregation in donor-acceptor blends over time is a function of materials and temperature. At moderate temperatures of 50-80 C, the problem is more severe in MDMO-PPV PCBM than P3HT PCBM blend films. This... 

Fig.31 I-V measurements of P3HT PCBM solar cells under 80mW/cm AM 1.5 solar spectrum simulation (light). The photocurrent and the diode characteristics improved from untreated (U, squares) over thermal annealing (T, open circles) to thermal annealing in combination with the application of external voltage (T + I, open triangles), (Reproduced with permission from [172], 2003, Wiley-VCH)...

Fig. 32 Absorption spectra of a P3HT PCBM composite film as cast (solid curve) and after four successive thermal annealing steps, as indicated in the legend. The PCBM concentration is 67%. (Reprinted with permission from [175], 2004, Institute of Physics Publishing)...

Erb et al. investigated the crystalline structure of P3HT PCBM bulk heterojunctions by grazing incidence X-ray diffraction (GID-XRD) [181], showing... 

Fig. 34 TEM images in combination with electron diffraction of a untreated and b thermally annealed P3HT PCBM blend films. (Reprinted with permission from [179], 2005, American Chemical Society)...

Fig. 35 Diffraction diagram (grazing incidence) of untreated and annealed P3HT PCBM blend films deposited on glass/ITO/PEDOT PSS substrates left). The corresponding a-axis orientation of the crystals is shown on the right. (Reproduced with permission from [181], 2005, Wiley-VCH)...

Fig. 36 XRD crystallinity (a) and absorption coefficient (b) of P3HT PCBM blends spin cast from either chlorobenzene (left) or chloroform (right) at various annealing temperatures. Interestingly, the increase in crystallinity is accompanied by a quantitatively correlated increase in optical absorption in the 2.0-2.5 eV region. (Reprinted from [183], 2006, with permission from Elsevier)...

Recently there have been several reports published on 4-5% record efficiencies obtained on the P3HT PCBM bulk heterojunction solar cell [18-21,165,188-190]. Ma et al. showed that annealing temperatures of 150 °C are required to obtain the highest efficiencies [18]. The authors assigned part... 

Fig. 37 AFM images of P3HT-PCBM (a-c) and P3HT-PCBG (d-f) blend films spin cast on glass. The images show unheated films (a and d), films annealed for 4 min at 140 °C (b and e), and films annealed for 1 h at 140 °C (c and f) [186]. (Reproduced by permission of The Royal Society of Chemistry)...

With the prospect of long-term stability [185,188] and the abiUty to print polymer solar cells [188] with power conversion efficiencies of 4-5%, EQEs of over 75%, internal quantum efficiencies approaching unity [194], and fill factors of almost 70% [18,21], the P3HT PCBM system is at the moment highly optimized. The main limitations in reaching larger power conversion effiden-... 

Fig. 41 short circuit current (A), power conversion efficiency (B), fill factor (C), and open circuit voltage (D) of a number of P3HT PCBM devices using different weight fractions (x-axis) as compared to the unfractionated sample. Clearly the larger weight fractions yield better values for all parameters investigated. (Reprinted with permission from [193], 2005, American Chemical Society)... 

Fig. 68 Current density-voltage characteristics of P3HT PCBM devices under AM 1.5G conditions using ITO on glass (open circles) and flexible SWNTs on PET (solid squares) as the anodes, respectively. Insets schematic of device and photograph of the highly flexible cell using SWNTs on PET. (Reprinted with permission from [333], 2006, American Institute of Physics)...

Fig. 3. %MR as a function of magnetic field for a typical RRP3HT based diode and a P3HT PCBM bulk heterojunction solar cell at room temperature showing almost negligible MR of good solar cells compared to the diodes.

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