On understanding bandgap bowing and optoelectronic quality in Pb–Sn alloy hybrid perovskites

Abstract

Experimental insights regarding bandgap evolution in hybrid perovskite alloys and the optimal small-bandgap absorber composition desired for next-generation perovskite tandems.

Controlling the Growth Kinetics and Optoelectronic Properties of 2D/3D Lead–Tin Perovskite Heterojunctions

“…We show the absorbance onset variation of both the higher and lower energy features in Figure b, revealing a bowing behavior for both the 2D and 3D domains, with minima for both domains at a Pb:Sn ratio of y = 0.75. The bowing behavior is a well‐established phenomenon in 3D Pb:Sn perovskites, but here we find that it also occurs in low‐dimensional 2D domains. The origin of the bowing behavior even in 3D perovskites is still debated.…”

“…perovskites, [19][20][21][22][23][26][27][28]52,53] but here we find that it also occurs in low-dimensional 2D domains. The origin of the bowing behavior even in 3D perovskites is still debated.…”

“…The bandgap can be lowered via B‐site engineering through total or partial Pb 2+ substitution with tin Sn 2+ , with the lowest achievable bandgap of the mixed system to date reported to be ≈1.2–1.3 eV. Sn‐substitution brings the added benefit of reducing or removing toxic Pb . The observed stability of the perovskite films is however reduced upon Sn‐substitution as Sn 2+ undergoes rapid oxidation to Sn 4+ , disrupting the perovskite lattice, introducing a self‐doping effect, and creating important carrier recombination centers that decrease the carrier diffusion length, lifetime, and the final device performance .…”

A Dopant‐Free Polymeric Hole‐Transporting Material Enabled High Fill Factor Over 81% for Highly Efficient Perovskite Solar Cells

“…Organic–inorganic hybrid perovskite solar cells (PVSCs) have attracted tremendous scientific attentions among the photovoltaic community because of their superb power conversion efficiencies (PCEs) and facile solution processability . Perovskite materials not only possess remarkable semiconducting properties such as broad and intense light absorption, long charge carrier lifetime and diffusion length, high electron/hole mobility and tunable bandgaps, but also have the light weight and solution processability features of organic semiconductors . In the past few years, the record PCE of PVSCs has been dramatically increased from 3.8% to 24.2%, which is on part with prevailing inorganic thin films photovoltaic technologies.…”

Managing Phase Purities and Crystal Orientation for High‐Performance and Photostable Cesium Lead Halide Perovskite Solar Cells

“…For a two‐junction tandem cell, with a crystalline silicon or Cu(In, Ga)Se 2 thin film that has a bandgap no wider than 1.2 eV as the bottom cell, a top cell with a bandgap in the range of 1.7–1.8 eV is required to provide an optimal short‐circuit photocurrent density ( J sc ) of over 18 mA cm −2 , to match that of the bottom cell. For all‐perovskite tandem cells, the wide‐bandgap layer could be up to 1.9 eV, because the narrow bandgap perovskite with metal alloying of lead and tin has a minimum bandgap beyond 1.2 eV . Recent works on all‐perovskite tandem cells used tin‐lead mixed perovskite with a narrow bandgap of 1.22, 1.25, and 1.27 eV and the wide bandgap perovskite of 1.77, 1.75, and 1.8 eV correspondingly.…”