TY - JOUR
T1 - The Impact of Sequential Fluorination of π-Conjugated Polymers on Charge Generation in All-Polymer Solar Cells
AU - Kranthiraja, Kakaraparthi
AU - Kim, Seonha
AU - Lee, Changyeon
AU - Gunasekar, Kumarasamy
AU - Sree, Vijaya Gopalan
AU - Gautam, Bhoj
AU - Gundogdu, Kenan
AU - Jin, Sung Ho
AU - Kim, Bumjoon J.
N1 - Publisher Copyright:
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2017/8/4
Y1 - 2017/8/4
N2 - The performance of all-polymer solar cells (all-PSCs) is often limited by the poor exciton dissociation process. Here, the design of a series of polymer donors (P1–P3) with different numbers of fluorine atoms on their backbone is presented and the influence of fluorination on charge generation in all-PSCs is investigated. Sequential fluorination of the polymer backbones increases the dipole moment difference between the ground and excited states (Δµge) from P1 (18.40 D) to P2 (25.11 D) and to P3 (28.47 D). The large Δµge of P3 leads to efficient exciton dissociation with greatly suppressed charge recombination in P3-based all-PSCs. Additionally, the fluorination lowers the highest occupied molecular orbital energy level of P3 and P2, leading to higher open-circuit voltage (VOC). The power conversion efficiency of the P3-based all-PSCs (6.42%) outperforms those of the P2 and P1 (5.00% and 2.65%)-based devices. The reduced charge recombination and the enhanced polymer exciton lifetime in P3-based all-PSCs are confirmed by the measurements of light-intensity dependent short-circuit current density (JSC) and VOC, and time-resolved photoluminescence. The results provide reciprocal understanding of the charge generation process associated with Δµge in all-PSCs and suggest an effective strategy for designing π-conjugated polymers for high performance all-PSCs.
AB - The performance of all-polymer solar cells (all-PSCs) is often limited by the poor exciton dissociation process. Here, the design of a series of polymer donors (P1–P3) with different numbers of fluorine atoms on their backbone is presented and the influence of fluorination on charge generation in all-PSCs is investigated. Sequential fluorination of the polymer backbones increases the dipole moment difference between the ground and excited states (Δµge) from P1 (18.40 D) to P2 (25.11 D) and to P3 (28.47 D). The large Δµge of P3 leads to efficient exciton dissociation with greatly suppressed charge recombination in P3-based all-PSCs. Additionally, the fluorination lowers the highest occupied molecular orbital energy level of P3 and P2, leading to higher open-circuit voltage (VOC). The power conversion efficiency of the P3-based all-PSCs (6.42%) outperforms those of the P2 and P1 (5.00% and 2.65%)-based devices. The reduced charge recombination and the enhanced polymer exciton lifetime in P3-based all-PSCs are confirmed by the measurements of light-intensity dependent short-circuit current density (JSC) and VOC, and time-resolved photoluminescence. The results provide reciprocal understanding of the charge generation process associated with Δµge in all-PSCs and suggest an effective strategy for designing π-conjugated polymers for high performance all-PSCs.
KW - all-polymer solar cells
KW - charge generation
KW - dipole moment
KW - exciton dissociation
KW - sequential fluorination
UR - http://www.scopus.com/inward/record.url?scp=85019772481&partnerID=8YFLogxK
U2 - 10.1002/adfm.201701256
DO - 10.1002/adfm.201701256
M3 - Article
AN - SCOPUS:85019772481
SN - 1616-301X
VL - 27
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 29
M1 - 1701256
ER -