A dual functional molecule for perovskite/P3HT interface to achieve stable perovskite solar cells

Abstract

After the introduction of spiro-OMeTAD as a hole transport material (HTM), the efficiency of perovskite solar cells (PSCs) has skyrocketed. However, dopants in spiro-OMeTAD make PSCs vulnerable to moisture and heat. Furthermore, the cost of spiro-OMeTAD is quite high, impeding the commercialization of PSCs. Therefore, the demand for HTMs that are dopant-free and cost-effective is increasing. In this regard, P3HT satisfies these criteria, exhibiting low-cost, long term stability, and high hole mobility. Despite these advantages, the PSCs with P3HT showed a lower efficiency compared to those PSCs with spiro-OMeTAD. Herein, we newly synthesized and employed a dual functional molecule, octylammonium azide (OAN₃). The ammonium ion could interact with perovskite and passivate the defects in perovskite and the azide moiety could provide crosslinking sites with P3HT, improving both efficiency and long-term stability. As a result, the perovskite solar cells (PSCs) with OAN₃ obtained a maximum efficiency of 20.0%. In contrast, bare PSCs achieved a maximum efficiency of 13.8%. In addition, PSCs with OAN₃ maintained 90% and 82% of their initial efficiency under RH = 50–60% condition. However, the bare PSCs retained 38% of their initial efficiency under the same conditions.