Effect of BaTiO₃ powder as an additive in perovskite films on solar cells

Perovskite solar cells (PSCs) are considered to be ideal energy devices, where perovskite-type organic metal halides act as light-absorbing materials. In PSCs, the photoexcitons are extracted and separated to afford high photoelectric conversion efficiency under the action of the built-in electric field (E _bi). However, the current challenge is that a low E _bi cannot provide a sufficient driving force to separate photonic excitons, which causes the captured charges to escape from the deep energy-level defect state. Here, the ferroelectric material barium titanate (BaTiO₃) was directly introduced into the perovskite precursor solution to reduce the defection density (to 8.58 × 10¹⁷ cm^-3) in PSCs and promote the separation of photoexcitons. Furthermore, the addition of BaTiO₃ improved the quality of the perovskite film and significantly increased the photoelectric performance after the polarization treatment. This is mainly attributed to the residual polarization electric field generated by ferroelectric polarization, which increased the E _bi of the PSCs and the width of the depletion layer and inhibited the non-radiative recombination of carriers. This work provides a possibility to design and develop optoelectronic devices with high-efficiency optoelectronic response behavior.