Effect of solvent vapor annealing on TiOPc thin films and the application on hybrid solar cells

Rongbin Ye, Koji Ohta, Mamoru Baba

This article reports on effect of solvent vapor annealing on TiOPc thin films and the application on hybrid solar cells based on ZnO/TiOPc with DH-α6T as an electron blocking layer. The band gap shows a change for the TiOPc thin film solvent vapor annealed with various solvents, which may be due to the phase transition from amorphous to α-phase, β-form or α+β-form. The phase separation could be responsible for the variations of the optical properties. No significant change is observed in the π-π* transition at various phase behaviors. Device performance of hybrid solar cells could be improved and open-circuit voltage (VOC), short-circuit current (ISC) and power conversion efficiency (η) were enhanced by solvent vapor annealing, which originated from amorphous TiOPc films transformed into crystalline α-phase, β-form or α+β-form.  At α-TiOPc, the device achieved the highest performance with VOC, ISC and η of 0.57 V, 1.40 mA/cm2, and 0.22 %, respectively, which originated from α-TiOPc with the widest red and near-IR absorption band.