TY - JOUR
T1 - High open-circuit voltage small-molecule p-DTS(FBTTh2)2:ICBA bulk heterojunction solar cells-morphology, excited-state dynamics, and photovoltaic performance
AU - Ko Kyaw, Aung Ko
AU - Gehrig, Dominik
AU - Zhang, Jie
AU - Huang, Ye
AU - Bazan, Guillermo C.
AU - Laquai, Frédéric
AU - Nguyen, Thuc Quyen
N1 - Publisher Copyright:
© The Royal Society of Chemistry 2015.
PY - 2015/1/28
Y1 - 2015/1/28
N2 - The photovoltaic performance of bulk heterojunction solar cells using the solution-processable small molecule donor 7,7′-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2,6-diyl)bis(6-fluoro-4-(5′-hexyl-[2,2′-bithiophene]-5-yl)benzo[c][1,2,5]thiadiazole) (p-DTS(FBTTh2)2 in combination with indene-C60 bis-adduct (ICBA) as an acceptor is systematically optimized by altering the processing conditions. A high open-circuit voltage of 1 V, more than 0.2 V higher than that of a p-DTS(FBTTh2)2:PC70BM blend, is achieved. However, the power conversion efficiency remains around 5% and thus is lower than ∼8% previously reported for p-DTS(FBTTh2)2:PC70BM. Transient absorption (TA) pump-probe spectroscopy over a wide spectral (Vis-NIR) and dynamic (fs to μs) range in combination with multivariate curve resolution analysis of the TA data reveals that generation of free charges is more efficient in the blend with PC70BM as an acceptor. In contrast, blends with ICBA create more coulombically bound interfacial charge transfer (CT) states, which recombine on the sub-nanosecond timescale by geminate recombination. Furthermore, the ns to μs charge carrier dynamics in p-DTS(FBTTh2)2:ICBA blends are only weakly intensity dependent implying a significant contribution of recombination from long-lived CT states and trapped charges, while those in p-DTS(FBTTh2)2:PC70BM decay via an intensity-dependent recombination mechanism indicating that spatially separated (free) charge carriers are observed, which can be extracted as photocurrent from the device.
AB - The photovoltaic performance of bulk heterojunction solar cells using the solution-processable small molecule donor 7,7′-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2,6-diyl)bis(6-fluoro-4-(5′-hexyl-[2,2′-bithiophene]-5-yl)benzo[c][1,2,5]thiadiazole) (p-DTS(FBTTh2)2 in combination with indene-C60 bis-adduct (ICBA) as an acceptor is systematically optimized by altering the processing conditions. A high open-circuit voltage of 1 V, more than 0.2 V higher than that of a p-DTS(FBTTh2)2:PC70BM blend, is achieved. However, the power conversion efficiency remains around 5% and thus is lower than ∼8% previously reported for p-DTS(FBTTh2)2:PC70BM. Transient absorption (TA) pump-probe spectroscopy over a wide spectral (Vis-NIR) and dynamic (fs to μs) range in combination with multivariate curve resolution analysis of the TA data reveals that generation of free charges is more efficient in the blend with PC70BM as an acceptor. In contrast, blends with ICBA create more coulombically bound interfacial charge transfer (CT) states, which recombine on the sub-nanosecond timescale by geminate recombination. Furthermore, the ns to μs charge carrier dynamics in p-DTS(FBTTh2)2:ICBA blends are only weakly intensity dependent implying a significant contribution of recombination from long-lived CT states and trapped charges, while those in p-DTS(FBTTh2)2:PC70BM decay via an intensity-dependent recombination mechanism indicating that spatially separated (free) charge carriers are observed, which can be extracted as photocurrent from the device.
UR - http://www.scopus.com/inward/record.url?scp=84919934604&partnerID=8YFLogxK
U2 - 10.1039/c4ta06256f
DO - 10.1039/c4ta06256f
M3 - Article
AN - SCOPUS:84919934604
SN - 2050-7488
VL - 3
SP - 1530
EP - 1539
JO - JOURNAL OF MATERIALS CHEMISTRY A
JF - JOURNAL OF MATERIALS CHEMISTRY A
IS - 4
ER -
