• polymer solar cells;
  • conjugated polyelectrolyte;
  • liquid crystals;
  • solution processes

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.