Charge transfer balancing of planar perovskite solar cell based on a low cost and facile solution-processed CuO x as an efficient hole transporting layer

Planar perovskite solar cells are known for their ease of fabrication and considerable efficiency. Hole transport layer in these cells is however mostly either expensive organic spiro-OMeTAD or hydrophilic PEDOT: PSS polymer which reduces cell lifespan due to its acidic nature. Copper oxide, on the other hand, is a non-toxic inorganic alternative. It can be synthesized through a facile solution-based process, requiring no vacuum system or N2 glovebox, which makes it conveniently adaptable to large-scale production. Inverted planar perovskite solar cells with CuOx as hole transport layer were studied. To balance the charge transfer in the device and avoid the charge accumulation in the bulk and interfaces, CuOx layer was deposited with different thicknesses. As verified by PL tests, quenching of the deposited CuOx layer was comparable to PEDOT: PSS layer which signifies its effectiveness as a hole transport layer. Optimum observed results were for a cell with an efficiency of 6.26%, Voc of 0.71 V, Jsc of 12.87 mA/cm2, and fill factor of 0.69. Consistent with J–V measurements, electrochemical impedance spectroscopy indicated a significant increase in charge transport resistance between hole transport layer and perovskite film as the CuOx film thickness was increased from 55 nm to 75 nm.