A facile molecularly engineered copper (II) phthalocyanine as hole transport material for planar perovskite solar cells with enhanced performance and stability. (January 2017) - Yang, Guang
Abstract: Perovskite solar cells (PSCs) demonstrate huge potential in photovoltaic conversion, yet their practical applications face one major obstacle: their instability. As to conventional hole transport materials (HTMs) such as spiro-OMeTAD, their future commercialization maybe hampered for the cost and instability. Here, we report a new HTM of copper (II) phthalocyanine with octamethyl-substituted function groups (CuMe2 Pc). Unlike the normal edge on orientation of pristine copper (II) phthalocyanine (CuPc), we found that CuMe2 Pc could form face-on molecular alignment when deposited on perovskite via vacuum thermal evaporation, resulting in higher hole mobility, more condense thin film structure and more hydrophobic surface. These properties are more favorable for hole transport and moisture resistance applications in PSCs. PSCs with planar structure were fabricated and tested, utilizing different phthalocyanines and spiro-OMeTAD as HTMs. PSCs with CuMe2 Pc showed 25% higher power conversion efficiency (PCE) compared with those with CuPc. Furthermore, beneficial from the hydrophobic nature of CuMe2 Pc, the devices with CuMe2 Pc as HTM show improved stability and retained over 95% of their initial efficiencies even after storage in the humidity about 50% for 2000 h without encapsulation. This study demonstrates that CuMe2 Pc is a potential HTM for fabricating low-cost and efficient PSCs with long-term stability. Graphical abstract: Planar perovskite solar cells employed CuMe2 Pc as hole transport material shows high performance with PCE up to 15.73% and excellent operation stability. Highlights: Copper (II) phthalocyanine was substituted with octamethyl function groups (CuMe2 Pc). CuMe2 Pc can form lying down (face on) molecular alignment. CuMe2 Pc possesses high hole mobility, condense structure and hydrophobic surface. The device with CuMe2 Pc as HTM shows improved stability and enhanced performance.