Improvement of performance of perovskite solar cells through BaTiO<sub>3</sub> doping regulated built-in electric field

Abstract

The preparation of hybrid perovskite solar cells is expensive and environmentally demanding. Carbon-based HTL-free perovskite solar cells (C-PSCs) have attracted much attention because they replace the expensive precious metal electrode and remove the poor stability of the hole transport material. However, the improvement of efficiency is hampered by poor carrier separation and transport performance within C-PSCs, while the enhancement of the built-in electric field can improve the carrier transport performance, thus enhancing photoelectric performance. The built-in electric field can be regulated by doping. The anomalous photovoltaic effect and the built-in electric field of ferroelectric material play an important role in the field of optoelectronics. In this work, a simple and effective method is developed to improve the performance of perovskite solar cells via the combination of internal doping of ferroelectric polymer and external control of electric field. Ferroelectric material barium titanate (BaTiO<sub>3</sub>) powder is added into perovskite precursor solution as an additive to prepare C-PSCs, which can improve the perovskite film morphology, reduce the film defect density, and enhance the carrier transport performance of C-PSCs. The results show that when the addition of BaTiO<sub>3</sub> is 1.0% (mass fraction), the perovskite film is uniform and dense, and the photoelectric conversion efficiency of the cell is the highest. After the forward voltage polarization treatment, the residual polarized electric field of ferroelectric material BaTiO<sub>3</sub> increases the built-in electric field, which provides sufficient power for realizing carrier transport and extraction, thus inhibiting the occurrence of non-radiative recombination. At the same time, the depletion layer width is increased, and the reverse saturation current is reduced, so the cell performance is significantly improved. The optimal device efficiency is 9.02%. This work provides an efficient strategy for regulating the built-in electric field by doping perovskite absorption layer.