Mitigating Open-Circuit Voltage Loss in Pb–Sn Low-Bandgap Perovskite Solar Cells via Additive Engineering

Abstract

Lead (Pb)–Tin (Sn) mixed perovskites suffer from large open-circuit voltage (V oc) loss due to the rapid crystallization of perovskite films, creating Sn and Pb vacancies. Such vacancies act as defect sites expediting charge carrier recombination, thus hampering the charge carrier dynamics and optoelectronic properties of the perovskite film. Here, we report the passivation of these defects using a controlled amount of 2-phenylethylazanium iodide (PEAI) in perovskite precursor solution as a dopant to enhance the performance of the 1.25 eV Pb–Sn low-bandgap perovskite solar cell. It was found that the incorporation of PEAI in the perovskite precursor not only improves the perovskite film quality and crystallinity but also lowers the electronic disorder, thereby enhancing the open-circuit voltage up to 0.85 V, corresponding to V oc loss as low as 0.4 V and the power conversion efficiency up to 17.33%. The value of V oc loss obtained with this strategy is among the least obtained for similar band gap Pb–Sn low-bandgap perovskite solar cells. Furthermore, the ambient and dark self-stability of the PEAI-treated devices were also enhanced. This work presents a simple doping strategy to mitigate the V oc loss of Pb–Sn mixed low-bandgap perovskite solar cells.

Device Performance of Emerging Photovoltaic Materials (Version 2)

“…The V oc optimization of tandem solar cells must address the challenges from each individual single junction sub‐cell, besides those common to the multijunction structure, such as the shunting of sub‐cells. [ 26–28 ] For instance, low‐ E g ‐perovskite‐based devices may present low V oc due to high electronic disorder [ 29 ] and large band offsets at the perovskite/ETL interface, [ 30 ] whereas wide‐ E g ‐perovskite‐based cells can suffer from photoinduced phase segregation [ 31 ] and energetic misalignment at the perovskite/HTL interface. [ 32 ] For OPV devices, the V oc losses have been associated with the offsets at the donor–acceptor heterojunction and the fast charge recombination in the organic semiconductors.…”

The role of A-site composition in the photostability of tin–lead perovskite solar cells

“…Devices based on the typical MAFA double cation or the CsMAFA triple cation compositions have consistently retained >95% of their original PCE after 1000 hours under dark and inert conditions. 4,30–34 However, upon light illumination, efficiency losses of around 10% already exist after 450 h under 1 sun. 6 In contrast, MA-free devices based on the CsFA mixture maintained their initial efficiency even after 1000 h of operation under 1 sun at 85 °C.…”

Impedance Spectroscopy for Metal Halide Perovskite Single Crystals: Recent Advances, Challenges, and Solutions

“…Even so, the remarkable structural, optical, and electronic properties of perovskite materials provide the same outstanding characteristics of high absorption coefficient, long carrier diffusion length, and long carrier lifetime in almost any morphology they present. − However, the perovskite material used in most of the high-performance optoelectronic devices has a polycrystalline nature with high quality, fabricated through solution processing techniques such as spin coating, − drop-casting, doctor-blading, or dip-coating . Despite the high crystallinity usually shown for polycrystalline perovskite films, a high density of defects, especially at the grain boundaries, , could act as recombination centers, reducing the maximum PCE achievable.…”