Acta Physico-Chimica Sinica

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Controllable Formation of PbI2 and PbI2(DMSO) Nano Domains in Perovskite Films through Precursor Solvent Engineering

Wusong Zha1,2, Lianping Zhang2, Long Wen3, Jiachen Kang2, Qun Luo2,4, Qin Chen3, Shangfeng Yang5, Chang-Qi Ma2,4   

  1. 1 Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, Jiangsu Province, P. R. China;
    2 Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, Jiangsu Province, P. R. China;
    3 Institute of Nanophotonic, Jinan University, Guangzhou 511443, P. R. China;
    4 Suzhou Institute of Nano-Tech and Nano-Bionics Nanchang, Chinese Academy of Sciences, Nanchang 330200, P. R. China;
    5 Department of Materials Science and Engineering, Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, P. R. China
  • Received:2020-03-09 Revised:2020-04-05 Published:2020-04-15
  • Supported by:
    The project was supported by the Natural Science Foundation of Jiangsu Province, China (BK20181197), the Natural Science Foundation of Jiangxi Province, China (20181BAB206017), the Youth Innovation Promotion Association, CAS (2019317), and the National Natural Science Foundation of China (51773224).

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Abstract: Perovskite solar cells (PSCs) attract much attention for their high efficiency and low processing cost. Power conversion efficiencies (PCEs) higher than 25% have been reported in literature, demonstrating the excellent application prospect of PSCs. In general, the crystallinity and the film composition of perovskite thin films are significant factors in determining device performance. Much effort has been made to control the growth process of perovskite films through the use of additives, passivation layers, special atmosphere treatments, precursor regulation etc. Among these methods, precursor solvent engineering is a simple and direct way to control the perovskite quality, but the controllability of components through solvent engineering is still difficult and has not yet been reported. Herein, we report the controlled formation of PbI2 and PbI2 with dimethyl sulfoxide (DMSO) nano domains through precursor solvent engineering. In particular, tuning the solvent content of the dimethyl sulfoxide:1,4-butyrolactone:N,N-dimethylformamide (DMSO:GBL:DMF) in the perovskite precursor solution, controlled the content of PbI2 and PbI2(DMSO) domains. Due to the lower boiling point and weaker coordination of DMF relative to DMSO, part of methylammonium iodide (MAI) would escape from the wet films during the evaporation process. Therefore, the PbI2(DMSO) can't completely convert to perovskite crystals and is retained in the final films as residual PbI2(DMSO) domains. Both UV-vis absorption spectrum and XRD spectrum confirmed the existence of PbI2 and PbI2(DMSO) domains. Importantly, the content of PbI2(DMSO) was controllable by simply changing the relative proportion of DMF. With an increase in the DMF content, the residual PbI2(DMSO) domains gradually increase. In addition, the influence of PbI2 and PbI2(DMSO) domains on the device performance was systematically investigated. The formation of PbI2(DMSO) domains caused a decrease in external quantum efficiency (EQE) of the device over 300-425 nm, and consequently decreased the device performance. That was because the PbI2(DMSO) domain has strong absorption over 300-425 nm. Therefore, the PbI2(DMSO) domains would absorb the photons over 300-425 nm prior to the perovskite, however the photons absorbed by the PbI2(DMSO) domains are not converted into the photocurrent. Thus, the perovskite solar cell containing PbI2(DMSO) showed an EQE loss over 300-425 nm in the EQE spectra. This work provides a simple method to control the components, especially the content of the PbI2(DMSO) domains, in perovskite films through regulating the precursor solvent. Additionally, this work revealed a PbI2(DMSO) domain related EQE loss phenomenon, highlighting the importance of controlling this component.

Key words: Perovskite solar cell, PbI2, PbI2(DMSO), Perovskite precursor, External quantum efficiency

MSC2000: 

  • O649