Superior Textured Film and Process Tolerance Enabled by Intermediate‐State Engineering for High‐Efficiency Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) have attracted intense research interest due to their unique properties, including low cost, large-scale processability, and high efficiency. In the past several years, the PSC field has witnessed a remarkable increase in power conversion efficiency (PCE) from 3.8% to over 25%, [1] which was comparable to the most established decades-old commercial photovoltaic technologies. To date, most of the highly efficient PSCs were prepared by the solution-chemistry approach. [2][3][4][5][6][7] However, for scaled-up production, many issues, such as the wide processing window, light trapping (which has been widely used in traditional thinfilm solar cells), and fabrication of scaledup perovskite film with high-quality, remain to be solved.The "annealing window" (the storage time of the intermediate-state films As the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is increased to as high over 25%, it becomes pre-eminent to study a scalable process with wide processing window to fabricate large-area uniform perovskite films with good light-trapping performance. A stable and uniform intermediate-state complex film is obtained by using tetramethylene sulfoxide (TMSO), which extends the annealing window to as long as 20 min, promotes the formation of a high-quality perovskite film with larger grains (over 400 nm) and spontaneously forms the surface texture to result in an improved fill factor and open-circuit voltage (V oc ). Moreover, the superior surface texture significantly increases the long-wavelength response, leading to an improved short-circuit current density (J sc ). As a result, the maximum PCE of 21.14% is achieved based on a simple planar cell structure without any interface passivation. Moreover, a large area module with active area of 6.75 cm 2 is assembled using the optimized TMSO process, showing efficiency as high as 16.57%. The study paves the way to the rational design of highly efficient PSCs for potential scaled-up production.

Structural Design for Efficient Perovskite Solar Modules

“…In this article, the perovskite films were fabricated by vacuum‐quenching solution approach (the detailed fabrication process is shown in the Experimental Section) due to its high reproducibility and usability on large area. [ 28 ] At the third step, we removed part of the covered redundant materials by laser (1064 nm) patterning for exposing FTO, while these bare FTO parts were covered by patterned gold electrode via thermal evaporation. The dimensions of different parts (etching pattern, mask for evaporating, and mask for testing) are shown in Figure S2, Supporting Information.…”

A Synergistic Precursor Regulation Strategy for Scalable Fabrication of Perovskite Solar Cells

“…Compare with DMSO, TMSO is a strong ligand with low vapor pressure (0.012 mmHg at 25 °C), it could restrain the reaction between organic salts and lead salts and formed a stable intermediate‐phase film, meanwhile, most of TMSO would be remained in the intermediate film after vacuum quenching. [ 14 ] In other words, all nucleation event (α‐phase and δ‐phase) would be suppressed and low nucleation density would be obtained when TMSO was used, low nucleation density would lead to the growth of larger grains after annealing. Herein, Cs + became less sensitive to the effect of nucleation density due to the use of TMSO.…”

“…[ 8–13 ] Ligands (or additive) can form complexes with perovskite precursors and change the Gibbs free energy in the solution system, thereby regulating the nucleation density and crystallization process. In our previous study, [ 14 ] tetramethylene sulfoxide (TMSO) was found to be a strong Lewis base, which could react with almost all perovskite precursors to form stable intermediate phase. Hence, TMSO restrained the reaction between lead salts and organic salts, thus hindered the nucleation process and reduced the crystallization rate.…”

“…[ 24 ] In contrast, for the vacuum quenching method, the solvent is removed by negative pressure, in particularly, the ligand can be retained in the film due to the difference in vapor pressure between ligand and solvent. [ 14,25,26 ] Therefore, the high replicability and versatility of this method appears to be more suitable for large‐scale production than the antisolvent‐involved approach. In addition, many strategies involved in the antisolvent‐participated method, such as additives engineering [ 13,27–29 ] and component engineering, [ 30,31 ] are still applicable in vacuum quenching method.…”

Small Molecule Modulator at the Interface for Efficient Perovskite Solar Cells with High Short‐Circuit Current Density and Hysteresis Free

“…The MI modified PEDOT: PSS film also slight roughens the surface of perovskite films ( Figure S6, Supporting Information), which means the contact area between the perovskite layer and ETL (PCBM) becomes larger and better for electron migration. [59] To further investigate the crystal growth of perovskite films with and without MI modification, the cross-section SEM image of the PSCs were tested in Figure 2e,f. Comparing with the reference devices, the cross-section of perovskite films with MI modification seems to be slightly better.…”