Boundary Engineering of Counter Electrodes for Dye‐Sensitized and Perovskite Solar Cells

Summary

Hybrid organic‐inorganic perovskites (CH₃NH₃PbI₃) demonstrated to be an attractive material for photovoltaic applications yielding high performances. In a typical planar structure perovskite solar cell (SnO₂:F(FTO)/compactTiO₂/CH₃NH₃PbI₃/spiro‐OMeTAD/Au) the CH₃NH₃PbI₃ layer is sandwiched between an electron transport layer (TiO₂) and a hole transport layer (spiro‐OMeTAD). The efficiency, hysteresis, stability and open circuit voltage of the cells are determined by the perovskite contacts. The interface TiO₂/CH₃NH₃PbI₃ which is affected by the difference in their thermal expansion coefficients and lattice mismatch which could result in interfacial defects which act as capacitor for charge trapping and/or charge accumulation.

In this chapter, we have used different circuit models for the simulation of the I‐V curves and compared to experimentally obtained I‐V curves showing strong hysteresis. The photovoltaic response of perovskite, dye‐sensitized and c‐Si solar cells are analyzed at different light intensity conditions. At low light intensity high capacitive currents of perovskite solar cells have been detected which are related to the origin of the strong I‐V hysteresis of this type of devices. For accurate evaluation of PSCs showing I‐V hysteresis, stabilized measurements of power conversion efficiencies at maximum power point are suggested.