Scientists China's Zhengzhou University, Xi'an Jiaotong University and Chinese Academy of Sciences (CAS) have designed a solar cell based on low-dimensional Ruddlesden-Popper (LPDR) perovskite that is said to have improved carrier transport properties.
The team explained that the new cells are more stable compared to regular 3D perovskite solar cells and are suitable for building-integrated photovoltaics (BIPV), conventional solar, and wearable devices.
Ruddlesden-Popper perovskites have often been studied as materials that can improve stability against humidity and lower encapsulation costs. They are considered suitable for top-layer materials for conventional perovskite solar cells.
The researchers used a LDRP based on γ-aminobutyric acid (GABA) as the organic spacer cation and a type of lead-halide perovskite known as methylammonium lead iodide (MAPbI3). They explained that the GABA-MAPbI3 film delivers an improved carrier mobility of 1.61 cm2 and charge (electron and hole) diffusion length over 700 nm.
The cell configuration consisted of an indium tin oxide (ITO) substrate, a tin(IV) oxide (SnO2) buffer layer, the 2D perovskite absorber, a spiro-OMeTAD hole-blocking layer, and a metal contact. The team said the use of the LDPR results in a cell's power conversion efficiency of 18.73%, which compares to 16.14% in a reference device without the addition of GABA.
In addition, according to the team, the devices exhibited excellent stability under continuous illumination, ambient atmosphere, 65 C, and 85% relative humidity. They speculated that the electrons of GABA can push the excitonic states outward from the band tails via hydrogen-bonding interaction.
The scientists claim that hydrogen-bonding interactions between the carboxyl groups of the bilayer GABA spacer cations bridge the charge transfer channel, while also promoting the optimization of the energy band structure responsible for the light absorption.