5 years ago

DMF as an Additive in a Two-Step Spin-Coating Method for 20% Conversion Efficiency in Perovskite Solar Cells

DMF as an Additive in a Two-Step Spin-Coating Method for 20% Conversion Efficiency in Perovskite Solar Cells
Xin Xu, Huijue Wu, Dongmei Li, Yanhong Zhao, Yanhong Luo, Jiangjian Shi, Qingbo Meng, Yuzhuan Xu, Jionghua Wu
DMF as an additive has been employed in FAI/MAI/IPA (FA= CH2(NH2)2, MA = CH3NH3, IPA = isopropanol) solution for a two-step multicycle spin-coating method in order to prepare high-quality FAxMA1–xPbI2.55Br0.45 perovskite films. Further investigation reveals that the existence of DMF in the FAI/MAI/IPA solution can facilitate perovskite conversion, improve the film morphology, and reduce crystal defects, thus enhancing charge-transfer efficiency. By optimization of the DMF amount and spin-coating cycles, compact, pinhole-free perovskite films are obtained. The nucleation mechanisms of perovskite films in our multicycle spin-coating process are suggested; that is, the introduction of DMF in the spin-coating FAI/MAI/IPA solution can lead to the formation of an amorphous phase PbX2–AI–DMSO–DMF (X = I, Br; A = FA, MA) instead of intermediate phase (MA)2Pb3I8·2DMSO. This amorphous phase, similar to that in the one-step method, can help FAI/MAI penetrate into the PbI2 framework to completely convert into the perovskite. As high as 20.1% power conversion efficiency (PCE) has been achieved with a steady-state PCE of 19.1%. Our work offers a simple repeatable method to prepare high-quality perovskite films for high-performance PSCs and also help further understand the perovskite-crystallization process.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b08504

DOI: 10.1021/acsami.7b08504

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