390
A. Mishra
based devices (Lin et al. 2015). A polar solvent soluble zwitterion perylene diimide
zwitterion (PDI-z) consisted of sulfobetaine ion as terminal units was prepared and
employed as CIL. (Song et al. 2018) The fullerene-free PBDB-T:IT-M based devices
under optical condition gave a PCE of 11.2%. PDI-z can also found to alter the high
WF metals, such as Au, Cu, Ag, where PDI-z/Ag gave the best PCE of 9.38%.
The device using PDIN as CIL also gave a high PCE of 10.25%. Fullerene-free
ternary solar cells using PDIN interlayer have been fabricated showing excellent
PCE of 11.6% (Hu et al. 2018). The enhanced performance was due to the strong
and complementary absorption of the active layer and interfacial modification by
PDIN layer improving the charge extraction and dissociation.
Sun et al. used a zwitterionic rhodamine 101 as CIL and tested the device performance using various metal as top electrodes. The PCDTBT:PC 71 BM device with Al
as top electrode gave the best PCE 6.15% compared to 4.57 for Ca/Al or 3.8% for Al
alone (Sun et al. 2012). Similar effect was also observed for other metal electrodes
(Ag, Au, Cu) in combination with rhodamine 101.
By employing a water/alcohol soluble pyridinium salt F8PS (HOMO = 5.71 eV
and LUMO = −3.31 eV) as CIL in PCDTBT:PC 71 BM devices simultaneous
improvement of all photovoltaic parameters was observed. The PCE increased from
4.32% for the reference cell to 6.56% and V OC from 0.76 to 0.94 V (Ye et al. 2013).
The V OC improvement was due to the generation of interface dipoles and excellent
electron transfer/collection ability of the hydrophilic pyridinium salt.
Zhang et al. reported two hydrophobic materials FBF-N and FTBTF-N which
served CIL to modulate the atop-BHJ morphology (Zhang et al. 2014). Thus, the
PCE of PTB7:PC 71 BM device could be enhanced to 7.97 and 9.22% from 1.18%
for bare ITO without interlayer. The hydrophobic nature of backbone formed better
morphology and helped to improve the J SC and FF.
Vacuum-deposition of N,N-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDIC8) over ZnO layer modified the interface properties, reduced the WF of ZnO and
improve device performance of PTB7-Th:PC 71 BM device with PCE from 8.26 to
9.29% (Fan et al. 2017).
Ma and co-workers developed a CIL by doping sol-gel derived ZnO with a 1 wt%
perylene derivative PBI-H, which formed an N − Zn bond with ZnO by thermal
treatment and improved the electron mobility by an order of magnitude (5.10 ×
10
−4 for neat ZnO to 2.02 × 10
−3 cm
2 V
−1 s
−1 ). (Nian et al. 2015) The conductivity
also improved to 4.50 × 10
−3 S m
−1 . OSC devices with PTB7:PC 71 BM and PTB7Th:PC 71 BM photoactive layer generated an excellent PCEs of 9.01% and 10.5%,
respectively, which is independent of CIL thickness and higher than the device with
pure ZnO (7.4 and 8.3%). The WF of modified ITO/ZnO:PBI-H decreased to 3.8 eV
compared to 4.2 eV for bare ITO/ZnO indicating increased electron population on
the conduction band of ZnO and also pinned the WF of ITO near LUMO of PC 71 BM
forming good Ohmic contact with PC 71 BM. PBI-H blocks holes due to low lying
HOMO energy level. Furthermore, the PBI-H interlayer form self-assembled J-type
aggregate with absorption maximum at 650 nm, 80 nm red-shifted than the monomer
and formed nanofibril networks by non-covalent interactions efficient for charge
transport (Xie et al. 2015).
A. Mishra
based devices (Lin et al. 2015). A polar solvent soluble zwitterion perylene diimide
zwitterion (PDI-z) consisted of sulfobetaine ion as terminal units was prepared and
employed as CIL. (Song et al. 2018) The fullerene-free PBDB-T:IT-M based devices
under optical condition gave a PCE of 11.2%. PDI-z can also found to alter the high
WF metals, such as Au, Cu, Ag, where PDI-z/Ag gave the best PCE of 9.38%.
The device using PDIN as CIL also gave a high PCE of 10.25%. Fullerene-free
ternary solar cells using PDIN interlayer have been fabricated showing excellent
PCE of 11.6% (Hu et al. 2018). The enhanced performance was due to the strong
and complementary absorption of the active layer and interfacial modification by
PDIN layer improving the charge extraction and dissociation.
Sun et al. used a zwitterionic rhodamine 101 as CIL and tested the device performance using various metal as top electrodes. The PCDTBT:PC 71 BM device with Al
as top electrode gave the best PCE 6.15% compared to 4.57 for Ca/Al or 3.8% for Al
alone (Sun et al. 2012). Similar effect was also observed for other metal electrodes
(Ag, Au, Cu) in combination with rhodamine 101.
By employing a water/alcohol soluble pyridinium salt F8PS (HOMO = 5.71 eV
and LUMO = −3.31 eV) as CIL in PCDTBT:PC 71 BM devices simultaneous
improvement of all photovoltaic parameters was observed. The PCE increased from
4.32% for the reference cell to 6.56% and V OC from 0.76 to 0.94 V (Ye et al. 2013).
The V OC improvement was due to the generation of interface dipoles and excellent
electron transfer/collection ability of the hydrophilic pyridinium salt.
Zhang et al. reported two hydrophobic materials FBF-N and FTBTF-N which
served CIL to modulate the atop-BHJ morphology (Zhang et al. 2014). Thus, the
PCE of PTB7:PC 71 BM device could be enhanced to 7.97 and 9.22% from 1.18%
for bare ITO without interlayer. The hydrophobic nature of backbone formed better
morphology and helped to improve the J SC and FF.
Vacuum-deposition of N,N-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDIC8) over ZnO layer modified the interface properties, reduced the WF of ZnO and
improve device performance of PTB7-Th:PC 71 BM device with PCE from 8.26 to
9.29% (Fan et al. 2017).
Ma and co-workers developed a CIL by doping sol-gel derived ZnO with a 1 wt%
perylene derivative PBI-H, which formed an N − Zn bond with ZnO by thermal
treatment and improved the electron mobility by an order of magnitude (5.10 ×
10
−4 for neat ZnO to 2.02 × 10
−3 cm
2 V
−1 s
−1 ). (Nian et al. 2015) The conductivity
also improved to 4.50 × 10
−3 S m
−1 . OSC devices with PTB7:PC 71 BM and PTB7Th:PC 71 BM photoactive layer generated an excellent PCEs of 9.01% and 10.5%,
respectively, which is independent of CIL thickness and higher than the device with
pure ZnO (7.4 and 8.3%). The WF of modified ITO/ZnO:PBI-H decreased to 3.8 eV
compared to 4.2 eV for bare ITO/ZnO indicating increased electron population on
the conduction band of ZnO and also pinned the WF of ITO near LUMO of PC 71 BM
forming good Ohmic contact with PC 71 BM. PBI-H blocks holes due to low lying
HOMO energy level. Furthermore, the PBI-H interlayer form self-assembled J-type
aggregate with absorption maximum at 650 nm, 80 nm red-shifted than the monomer
and formed nanofibril networks by non-covalent interactions efficient for charge
transport (Xie et al. 2015).