Abstract
Perovskite solar cells, which represent the promise of future generation photovoltaic technology with the lowest cost and highest efficiency, have evoked widespread scientific and industrial interest. Through rational device architecture design, materials interface engineering as well as processing technique optimization, a recorded efficiency around 18% has been attained, showing great potential for commercialization to compete with traditional silicon solar cells. Although the device performance of perovskite solar cells improves unprecedently fast in last two years, the basic properties of metalorganic halide perovskite, MAPbX3 (X=Cl, Br, I), such as the role of cation and anion, for example, are still not well understood. Most of research focuses on the perovskite band gap tuning by changing the ratio of either anions (Br to I) or cations (FA to MA). However, up to date, the effect of anion in percursor solution on the perovskite crystal growth and film formation has not been well studied yet, which is highly likely to correlate with the device performance. In addition, there is a long debate on the existence and role of Cl in mixed-halide perovskite and the results from varied groups employing different characterization techniques are quite controversial. Fully understanding of these questions is critically important for the advancement of perovskite solar cell technology in the next few years. In this work, the effect of anion was systematically studied and we found that anion in precursor solution has great influence on the perovskite crystal growth and film formation. By materials engineering, both film morphology and processing time are greatly improved, which leads to enhanced performance in plannar heterojunction devices.