Effects of Annealing Conditions on ZnO Buffer Layer for Inverted Polymer Solar Cells

Chuan Liu,Zhiyang Gao,Chuannan Li,Jian Zhang,Lihua Zheng,Yuhui Gan

doi:10.4236/opj.2013.32b052

Abstract

A solution-processed zinc oxide (ZnO) thin film as the buffer layer with optimized processes especially the annealing conditions for inverted polymer solar cells (PSCs) has been demonstrated. Firstly the thickness of ZnO buffer layer was optimized, and different annealing conditions including temperature and time have also been taken into consideration. And the best Power Conversion Efficiency (PCE) 3.434% was observed when the ZnO buffer layer was spin–coated at 1500 rpm and annealed at 275℃ for 5 min, and AFM results showed that morphology of this ZnO film has the best uniformity which was beneficial to form high quality polymer composite active layer.

Highlights

Polymer solar cells (PSCs) offer a potentially low-cost, lightweight, flexible and scalable source of renewable energy
The best Power Conversion Efficiency (PCE) 3.434% was observed when the zinc oxide (ZnO) buffer layer was spin–coated at 1500 rpm and annealed at 275°C for 5 min, and atomic force microscopy (AFM) results showed that morphology of this ZnO film has the best uniformity which was beneficial to form high quality polymer composite active layer
Solar cells were fabricated with different rotation speed of ZnO, and annealed under the two temperatures 200°C and 275°C, their current density-voltage (J-V) characteristics are shown in Figures 2(a) and (b)

Summary

Introduction

Polymer solar cells (PSCs) offer a potentially low-cost, lightweight, flexible and scalable source of renewable energy. In the regular bulk heterojunction PSCs structure, transparent indium tin oxide (ITO) usually is used as the anode and low work function metal as the cathode. It brings the problem of low stability and efficiency. The low work function metal e.g. calcium used as the cathode in the regular structure, is replaced by a relatively nonreactive electron collection layer and transparent ITO film, and the stable metal such as Ag or Al can be used as the top anode of inverted PSCs, this significantly improves the air stability of the polymer solar cells. Vertical phase separation in polymer blends has proven to be advantageous in the inverted structure [5]

Methods

Results

Conclusion