A ternary cascade structure enhances the efficiency of polymer solar cells

Huang, Jen-Hsien; Velusamy, Marappan; Ho, Kuo–Chuan; Lin, Jiann-T’suen; Chu, Chih‐Wei

doi:10.1039/b918362k

Cited by 110 publications

(85 citation statements)

References 41 publications

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“…Since this discovery, numerous other materials combinations have demonstrated tunable V oc in devices having ternary-blend BHJs. [ 11,17,27,[31][32][33][34] Equally many other materials combinations have resulted in ternary-blend solar cells whose V oc is pinned to the smallest …”

mentioning

confidence: 99%

Structural Origins for Tunable Open‐Circuit Voltage in Ternary‐Blend Organic Solar Cells

Khlyabich

Rudenko

Thompson

et al. 2015

Adv Funct Materials

124

128

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Organic BHJ solar cells comprising ternary-blend absorbing layers, based either on two donors and one acceptor or one donor and two acceptors, provide an attractive and effective pathway to increase effi ciencies while preserving processing simplicity. [11][12][13][14][15][16][17][18][19][20][21][22] In early studies, the effi ciency enhancement of such solar cells was attributed to an increase in the spectral response upon the introduction of an additional donor having an absorption profi le that is complementary to that of the parent donor-acceptor pair, effectively increasing the number of harvested photons and ultimately the photocurrent. [ 11,13,16,18 ] Until recently, the opencircuit voltage ( V oc ) of such devices was thought to be pinned by the difference in the energy levels of the lowest unoccupied molecular orbital (LUMO) of the acceptor and the higher of the two highest occupied molecular orbitals (HOMO) in active layers comprising an acceptor and two donors. [ 23 ] Given that the third component that is introduced often has a smaller bandgap than the parent donor in order extend the spectral response of the existing active layer, it almost always has a higher lying HOMO compared to the parent donor. As such, the V oc of these devices are generally smaller than the V oc of counterpart solar cells comprising only the parent donor-acceptor pair. [ 13,14,18,[23][24][25][26] With a series of papers, Thompson and co-workers [ 11,12,19,[27][28][29][30] demonstrated that the V oc of ternary-blend solar cells need not be pinned by the smallest energy level difference of the constituents, as described above. In fact, with proper selection of materials combination for ternary-blend active layers, the V oc of these solar cells can be continuously tuned with composition between those derived from the HOMO energy levels of the individual donors. As such, the increase in short-circuit current densities ( J sc ) with the introduction of a third constituent in these solar cells need not come at the expense of V oc 's that are pinned to the smallest energy level difference of the constituents. By breaking this paradigm, Thompson and co-workers showed that ternary-blend solar cells with effi ciencies exceeding parent binary-blend solar cells while maintaining high fi ll factor (FF) can be made across the blend composition while maintaining the simplicity of processing. Since this discovery, numerous other materials combinations have demonstrated tunable V oc in devices having ternary-blend BHJs. [ 11,17,27,[31][32][33][34] Equally many other materials combinations have resulted in ternary-blend solar cells whose V oc is pinned to the smallest

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mentioning

confidence: 99%

Structural Origins for Tunable Open‐Circuit Voltage in Ternary‐Blend Organic Solar Cells

Khlyabich

Rudenko

Thompson

et al. 2015

Adv Funct Materials

124

128

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“…Another approach to increase the photocurrent generation in organic solar cells is the incorporation of additional lightabsorbing materials besides the required donor and acceptor, as in ternary blend bulk heterojunction devices [23][24][25] . In planar heterojunction devices, several mechanisms have been proposed to extract photocurrent from an additional active layer.…”

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confidence: 99%

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

et al. 2014

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In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Förster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.

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“…Figure 2 shows the UV-visible absorption spectrum of P3HT:PCBM (1:1) film with or without 8OCB additive. Three characteristic absorption peaks at 514, 550 and 605 nm could be observed for the as-spun P3HT:PCBM film after annealing at 70°C for 20 min [29]. In general, the three distinct absorption peaks could be attributed to the p-p* transition (511 nm) and p-p stacking (555 and 605 nm) of P3HT [30].…”

Section: Resultsmentioning

confidence: 92%

Improvement of the photovoltaic properties for P3HT:PCBM system annealed at the temperature in liquid crystalline regions induced by liquid crystal molecules

Shi

Zhou

et al. 2014

Polym. Bull.

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The poly(3-hexylthiophene):[6, 6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction organic photovoltaics (BHJ OPVs) showed a maximum value of 3.5 % by incorporating of 6 wt% nematic liquid crystals (NLCs) of 4-octyloxy-4 0 -cyanobiphenyls (8OCB) after annealing at the temperature of 70°C in liquid crystalline transitions. The 8OCB was immiscible with P3HT, and the melting temperature of P3HT was not influenced at 8OCB doping amount below 10 wt%. Based on the UV-vis analysis, the conjugation length and chain order of P3HT should be the highest at 8OCB content of 6 wt% after annealing at 70°C. The reflection peak of P3HT shifted to lower positions as the annealing temperature increasing from 70 to 130°C, indicating that PCBM and 8OCB molecules could be incorporated into the lamellar spacing of P3HT crystallites at high annealing temperatures. The improvement of the solar cell device after annealing at 70°C is probably due to the optimized phase separation morphology and relatively higher hole mobility in P3HT:PCBM:8OCB system. The 8OCB molecules in the liquid crystalline state are supposed to be a good template for the crystallization of P3HT, as well as the phase separation between P3HT and PCBM.

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A ternary cascade structure enhances the efficiency of polymer solar cells

Cited by 110 publications

References 41 publications

Structural Origins for Tunable Open‐Circuit Voltage in Ternary‐Blend Organic Solar Cells

Structural Origins for Tunable Open‐Circuit Voltage in Ternary‐Blend Organic Solar Cells

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

Improvement of the photovoltaic properties for P3HT:PCBM system annealed at the temperature in liquid crystalline regions induced by liquid crystal molecules

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