Optimization of the Power Conversion Efficiency of Room Temperature‐Fabricated Polymer Solar Cells Utilizing Solution Processed Tungsten Oxide and Conjugated Polyelectrolyte as Electrode Interlayer

Abstract

The utilization of a conjugated polyelectrolyte‐ionic liquid crystal (CPE‐ILC) complex as electron transporting layer (ETL) to improve the compatibility between the ITO and hydrophobic active layer and to promote the dipole orientation at cathode interface is reported. Simultaneously, a hole transporting layer (HTL) of solution processed tungsten oxide together with poly(2,6‐bis(trimethyltin)‐4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐4,6‐Dibromo‐thieno[3,4‐b]thiophene‐2‐carboxylic acid 2‐[2‐(2‐methoxy‐ethoxy)‐ethoxy]‐ethyl ester) (PBDTT‐TT‐TEG) efficiently shifts the work function of Ag electrode in this device. The interfacial modification of these interlayers achieves energy alignment at both electrodes. The power conversion efficiency (PCE) of the PSC based on ITO/PFN‐CbpSO/PBDTTT‐C‐T:PC70BM/PBDTT‐TT‐TEG/WO3/Ag with solution processed interlayers reaches to 7.8%. It is worthy to note that except for the electrodes, all layers of device are fabricated by solution process at room temperature and without annealing. In the case of incorporating ZnO layer into this device, the device efficiency further increases to 8.5%, which is the best value reported from PBDTTT‐C‐T:PC70BM‐based solar cells with solution processed interlayers at both electrodes so far.

Key Developments in Ionic Liquid Crystals

“…Examples of applications of ILCs are anisotropic tribology [ 146 ] and ion conductivity to be used in molecular electronics (solar cells, optoelectronic devices, etc .) [ 35 , 37 , 38 , 147 , 148 ], in directed synthesis approaches [ 149 ], including controlled nanoparticle synthesis, [ 150 , 151 ], alignment [ 152 ] or deposition [ 153 ], in ionic self-assembly [ 154 , 155 ] that builds complex structures from simple charged organic species and possibly in bio-catalysis [ 156 ] or sensing applications [ 25 , 98 ]. The near future will demonstrate which roles ILCs can play.…”

Inverted organic photovoltaic cells

“…Various studies have shown that the lifetime of inverted OPVs using the TMOs HELs can be increased dramatically. 409,[415][416][417] Our group also demonstrated that by using TMOs such as Fe 3 O 4 MNPs as the HEL in the conventional OPVs to eliminate the PEDOT:PSS, the device stability was significantly enhanced. 14 It should be noted that the degradation in OPVs comprises a complex range of mechanisms that presumably have not been completely identified.…”

Recent Advances in Bulk Heterojunction Polymer Solar Cells

“…These are incompatible with the high-throughput roll-to-roll process and thus are not cost effective. Therefore, various solution-processed methods were developed to prepare metal oxide films that include NiO, − V 2 O 5 , , CuO, WO 3 , , RuO 2 , CrO x , and NiAc . Due to space limitations, here we mainly discuss new solution-processing methods that have been developed to prepare molybdenum oxide (MoO 3 ) thin films, as these have proven most useful for OPVs.…”