Sequential Formation of Tunable‐Bandgap Mixed‐Halide Lead‐Based Perovskites: In Situ Investigation and Photovoltaic Devices

Abstract

Inorganic−organic hybrid perovskites MAPb(IxBr1−x)3 (0 < x < 1) hold promise for efficient multi‐junction or tandem solar cells due to tunable bandgap and improved long‐term stability. However, the phase transformation from Pb(IxBr1−x)2 precursors to perovskites is not fully understood which hinders further improvement of optoelectronic properties and device performance. Here, adaptation of the two‐step deposition method, which enables the direct probe into the growth dynamics of perovskites using in situ diagnostics, and a detailed view of the effects of solvent, lead halide film solvation, and Br incorporation and alloying on the transformation behavior is presented. The in situ measurements indicate a strong tendency of lead halide solvation prior to crystallization during solution‐casting Pb(IxBr1−x)2 precursor from a dimethyl sulfoxide (DMSO) solvent. Highly‐efficient intramolecular exchange is observed between DMSO molecules and organic cations, leading to room‐temperature conversion of perovskite and high‐quality films with tunable bandgap and superior optoelectronic properties in contrast to that obtained from crystalline Pb(IxBr1−x)2. The improved properties translate to easily tunable and a relatively higher power conversion efficiency of 16.42% based on the mixed‐halide perovskite MAPb(I0.9Br0.1)3. These findings highlight the benefits that solvation of the precursor phases, together with bromide incorporation, can have on the microstructure, morphology, and optoelectronic properties of these films.

Manipulated Crystallization and Passivated Defects for Efficient Perovskite Solar Cells via Addition of Ammonium Iodide

“…Organic–inorganic hybrid perovskite semiconductors have been widely used as the active layer material of optoelectronic devices such as solar cells, , light-emitting diodes, , and photodetectors. , These perovskite-based materials possess advantages such as high light absorption coefficients, tunable band gaps, low material cost, solution processability, etc. One of the most triumphant and widespread applications is the perovskite solar cell (PSC), which achieves the record efficiency of 25.5% from its original efficiency of 3.8% with an unprecedented pace. , In addition to the success in single junction solar cells, perovskite semiconductors with a tunable band gap and sharp absorption edge enable themselves as the ideal top cell for multijunction tandem solar cells, such as perovskite/perovskite or perovskite/Si tandem solar cells. − …”

“…Organic−inorganic hybrid perovskite semiconductors have been widely used as the active layer material of optoelectronic devices such as solar cells, 1,2 light-emitting diodes, 3,4 and photodetectors. 5,6 These perovskite-based materials possess advantages such as high light absorption coefficients, 7 tunable band gaps, 8 low material cost, 9 solution processability, 10 etc. One of the most triumphant and widespread applications is the perovskite solar cell (PSC), which achieves the record efficiency of 25.5% from its original efficiency of 3.8% with an unprecedented pace.…”

First‐principles study ofCs2Ti1−xMxBr6(M = Pb, Sn) and numerical simulation of the solar cells based onCs2Ti0.25Sn0.75Br6perovskite

“…For example, CsPbI 3, 19 CsSnI 3 exhibits a direct band gap due to the change in parity from VBM (even) to CBM (odd) but CsZnCl 3 , CsCaCl 3 exhibits an indirect band gap as the parity remains the same from VBM to CBM 7 . This new insight regarding the nature of band gap could be truly useful for designing direct band gap (A 2 BX 6 ) lead‐free perovskite materials 19‐22 for future solar technologies 23,24 …”

“…7 This new insight regarding the nature of band gap could be truly useful for designing direct band gap (A 2 BX 6 ) leadfree perovskite materials [19][20][21][22] for future solar technologies. 23,24 The present work addresses the issue of the high and indirect band gap of previously reported composition Cs 2 TiBr 6 by examining the impact of partially replacing "Ti" with M = Pb/Sn in Cs 2 Ti 1−x M x Br 6 . However, to emphasize the importance of our results, it is necessary to shed light on recent development based on the mix of perovskite materials with quantum dots (QDs).…”

Poly(vinylidene fluoride‐co‐hexafluoropropylene) additive in perovskite for stable performance of carbon‐based perovskite solar cells

“…Hybrid‐perovskite halide semiconductor is an emerging light‐harvesting material, which leads to moving forward for the outstanding performance in the field of photovoltaic (PV) device due to their high absorption coefficient, high charge carrier lifetime, high open‐circuit voltage, tunable bandgap, outstanding power conversion efficiency (PCE), and simple solution processable technique 1‐6 . The perovskite photovoltaic device has been developing rapidly with certified efficiency exceeding ~25.5%, which is comparable to existing crystalline silicon solar cell technologies 7 .…”