A new acceptor-donor-acceptor-structured nonfullerene acceptor ITCC (3,9-bis(4-(1,1-dicyanomethylene)-3-methylene-2-oxo-cyclopenta[b]thiophen)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d':2,3-d']-s-indaceno[1,2-b:5,6-b']-dithiophene) is designed and synthesized via simple end-group modification. ITCC shows improved electron-transport properties and a high-lying lowest unoccupied molecular orbital level. A power conversion efficiency of 11.4% with an impressive V of over 1 V is recorded in photovoltaic devices, suggesting that ITCC has great potential for applications in tandem organic solar cells.
A highly efficient fullerene-free polymer solar cell (PSC) based on PDCBT, a polythiophene derivative substituted with alkoxycarbonyl, achieves an impressive power conversion efficiency of 10.16%, which is the best result in PSCs based on polythiophene derivatives to date. In comparison with a poly(3-hexylthiophene):ITIC-based device, the photovoltaic and morphological properties of the PDCBT:ITIC-based device are carefully investigated and interpreted.
Two wide band gap polymer donors were developed for fullerene-free polymer solar cells. The photovoltaic performance of the PB3T:IT-M device processed by anisole achieved a high PCE of 11.9%.
Here,
taking a polythiophene derivative (PBDD4T) as a starting
polymer, we tried to increase the rotation barrier and hence stabilize
its backbone conformation by introducing fluorine into the β-
and β′-position of the α-linked bithiophene segments
and then synthesized a new polymer named as PBDD4T-2F. Our results
demonstrate that the rotation barrier between the α-linked bithiophene
significantly increases after the fluorination, so PBDD4T-2F has a
more stable backbone conformation than PBDD4T. Compared to PBDD4T,
PBDD4T-2F shows stronger aggregation effect in solution state and
more compact π–π stacking in solid thin film and
also possesses deeper HOMO level. These properties make PBDD4T-2F
being an ideal donor material in PSCs. When blended with PC71BM, a fullerene acceptor, the PBDD4T-2F-based device showed a power
conversion efficiency (PCE) of 9.04%, which is 38% higher than that
of the PBDD4T-based device; when blended with ITIC, a non-fullerene
acceptor, the PBDD4T-2F-based device showed a PCE of 8.69%, which
is almost 20 times higher than that of the PBDD4T-based device. What
is more, the tandem cell, in which the blend of PBDD4T-2F:PC61BM was used for making the front subcell, exhibited a high PCE of
10.12%. The photovoltaic results indicate that the fluorination is
an effective method to enhance interchain π–π interaction
for the polythiophene and hence to tune its photovoltaic properties
in PSCs, especially for the fullerene-free device based on ITIC.
A wide bandgap polymer donor PBDTS‐DTBTO is designed and synthesized, which shows an optical bandgap of 1.76 eV and strong π–π interaction. By using a low‐bandgap acceptor ITIC, power conversion efficiency over 9% is achieved in the fullerene‐free polymer solar cells (PSC) device. Furthermore, the PSC devices fabricated by PBDTS‐DTBTO:ITIC show relatively small sensitivity to variations of the active layer thickness.
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