Highly Efficient Fullerene‐Free Polymer Solar Cells Fabricated with Polythiophene Derivative

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current. The latter is the value of qV OC a solar cell with that bandgap would have at a temperature of 300 K illuminated by 1 sun unconcentrated illumination and assuming emission of luminescence into the 2π halfspace above the solar cell. [16][17][18][19] 2) qV OC SQ − qV OC rad (ΔE 2 ) is the loss due to the absorption edge being nonabrupt and therefore primarily due to radiative recombination below the bandgap. [20][21][22][23][24] 3) The third loss is due to nonradiative recombination (ΔE 3 ). As the first term ΔE 1 is unavoidable for any solar cell, the main opportunities for reducing E loss to improve the V OC lie in the other two terms.The second term, ΔE 2 , can be reduced by elevating the charge transfer (CT) state. For instance, it has been demonstrated that when the ionic potential (IP) and electronic affinity (EA) of a donor are nearly aligned with those of an acceptor, the energetic offset from E g to E CT can be very small, resulting in a negligible ΔE 2 . [20,21,25,26] In contrast, when the IP and EA of a donor are much larger than those of an acceptor, as observed in many OSCs based on polymer donors and fullerene acceptors, ΔE 2 can be as large as over 0.60 eV. [17,27,28] The third term, ΔE 3 , can be varied from 0.25 to 0.48 eV. [29][30][31][32][33][34][35] As is known, for an OSC under open-circuit condition, an electron-hole pair at the CT state transits to the ground state by either radiative recombination or nonradiative recombination, so the electroluminescence (EL) emission can be used as a tool to monitor the nonradiative recombination. [21,28,[31][32][33] There have been many studies to investigate ΔE 3 for OSCs based on various photoactive materials. [28,30,36] For instance, for an OSC based on the polymer donor P3TEA and acceptor SF-PDI2, the electroluminescence quantum efficiency (EQE EL ) was as high as 5 × 10 −5 , corresponding to a ΔE 3 of 0.26 eV, [20] while for OSCs based on polymer donors and fullerene acceptors, ΔE 3 can surpass 0.40 eV. [30,31] Up to date, the methodology for tuning ΔE 3 has not yet been established. Considering that ΔE 1 is unavoidable and ΔE 2 can be reduced to a negligible value, the modulation of ΔE 3 is critical in the field of OSCs.Here, we report a new method to reduce E loss in an OSC based on the polymer donor PBDB-T and nonfullerene acceptor IT-4F by incorporating a small molecular material named NRM-1 in the photoactive layer. We selected the PBDB-T:IT-4F system to conduct the study because the IP and EA of PBDB-T are much larger than those of IT-4F and the energetic offset between E g and E CT , referring to ΔE 2 , can be obviously Reducing energy loss (E loss ) is of critical importance to improving the photovoltaic performance of organic solar cells (OSCs). Although nonradiative recombination ( E loss nonrad ) is investigated in quite a few works, the method for modulating E loss nonrad is seldom reported. Here, a new method of depressing E loss is reported for nonfullerene OSCs. In addition to ternary-blend bulk heterojunction (BHJ) solar cells...

Section: Doi: 101002/aenm201901823mentioning

confidence: 69%

Reduced Nonradiative Energy Loss Caused by Aggregation of Nonfullerene Acceptor in Organic Solar Cells

Qin

Zhang

et al. 2019

Self Cite

“…[38] As displayed in Figure S7b (Supporting Information), the surface energy of ITIC (30.9 mN m −1 ) film is much higher than that of PTB7-Th . [39,40] The dependence of V oc on the light intensity for PTB7-Th:ITIC blend with incorporation of 0.6 vol% DIO showed a slope of 1.06 kT/q, compared to 1.52 and 1.84 kT/q for blend films with 0 and 1 vol% DIO, respectively. Since the neat PTB7-Th molecule does not contain nitrogen atoms whereas the neat ITIC molecule has nitrogen-containing components, the migration of ITIC can also be directly verified by X-ray photoelectron spectroscopy (XPS) measurements.…”

Section: Bis[5-(2-ethylhexyl)-2-thienyl]mentioning

confidence: 97%

Printed Nonfullerene Organic Solar Cells with the Highest Efficiency of 9.5%

Lin

Jin

Dong

et al. 2018

101

The current work reports a high power conversion efficiency (PCE) of 9.54% achieved with nonfullerene organic solar cells (OSCs) based on PTB7‐Th donor and 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene) (ITIC) acceptor fabricated by doctor‐blade printing, which has the highest efficiency ever reported in printed nonfullerene OSCs. Furthermore, a high PCE of 7.6% is realized in flexible large‐area (2.03 cm2) indium tin oxide (ITO)‐free doctor‐bladed nonfullerene OSCs, which is higher than that (5.86%) of the spin‐coated counterpart. To understand the mechanism of the performance enhancement with doctor‐blade printing, the morphology, crystallinity, charge recombination, and transport of the active layers are investigated. These results suggest that the good performance of the doctor‐blade OSCs is attributed to a favorable nanoscale phase separation by incorporating 0.6 vol% of 1,8‐diiodooctane that prolongs the dynamic drying time of the doctor‐bladed active layer and contributes to the migration of ITIC molecules in the drying process. High PCE obtained in the flexible large‐area ITO‐free doctor‐bladed nonfullerene OSCs indicates the feasibility of doctor‐blade printing in large‐scale fullerene‐free OSC manufacturing. For the first time, the open‐circuit voltage is increased by 0.1 V when 1 vol% solvent additive is added, due to the vertical segregation of ITIC molecules during solvent evaporation.

“…Energy Mater. [25,54] Since a portion of the photoinduced generated excitons are dissociated into holes and electrons in the BHJ structure, the exciton dissociation probability P(E,T) can be deduced using the estimated G max value. The G max and J sat values of the 3MT-Th:ITIC-based device (1.03 × 10 28 m −1 s −1 and 165.47 A m −2 , respectively) are about 20% higher than those of the PTB7-Th-based device, this can be attributed to the extended light absorption range of the 3MT-Th:ITIC blend (Table S7, Supporting Information).…”

Section: Photovoltaic Propertiesmentioning

confidence: 99%

Eco‐Friendly Solvent‐Processed Fullerene‐Free Polymer Solar Cells with over 9.7% Efficiency and Long‐Term Performance Stability

Park

Choi

Park

et al. 2017

A wide‐bandgap polymer, (poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(2,5‐(methyl thiophene carboxylate))]) (3MT‐Th), is synthesized to obtain a complementary broad range absorption when harmonized with 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (ITIC). The synthesized regiorandom 3MT‐Th polymer shows good solubility in nonhalogenated solvents. A film of 3MT‐Th:ITIC can be employed for forming an active layer in a polymer solar cell (PSC), with the blend solution containing toluene with 0.25% diphenylether as a nonhalogenated additive. The corresponding PSC devices display a power conversion efficiency of 9.73%. Moreover, the 3MT‐Th‐based PSCs exhibit excellent shelf‐life time of over 1000 h and are operationally stable under continuous light illumination. Therefore, methyl thiophene‐3‐carboxylate in 3MT‐Th is a promising new accepting unit for constructing p‐type polymers used for high‐performance nonfullerene‐type PSCs.