Charge transfer modification of inverted planar perovskite solar cells by NiO x /Sr:NiO x bilayer hole transport layer

Perovskite solar cells (PSCs) are the most promising commercial photoelectric conversion technology in the future. The planar p–i–n structure cells have advantages in negligible hysteresis, low temperature preparation and excellent stability. However, for inverted planar PSCs, the non-radiative recombination at the interface is an important reason that impedes the charge transfer and improvement of power conversion efficiency. Having a homogeneous, compact, and energy-level-matched charge transport layer is the key to reducing non-radiative recombination. In our study, NiO x /Sr:NiO x bilayer hole transport layer (HTL) improves the holes transmission of NiO x based HTL, reduces the recombination in the interface between perovskite and HTL layer and improves the device performance. The bilayer HTL enhances the hole transfer by forming a driving force of an electric field and further improves J sc. As a result, the device has a power conversion efficiency of 18.44%, a short circuit current density of 22.81 mA⋅cm−2 and a fill factor of 0.80. Compared to the pristine PSCs, there are certain improvements of optical parameters. This method provides a new idea for the future design of novel hole transport layers and the development of high-performance solar cells.