Precursor Engineering for All‐Inorganic CsPbI₂Br Perovskite Solar Cells with 14.78% Efficiency

Abstract

The optoelectronic properties of perovskite films are closely related to the film quality, so depositing dense, uniform, and stable perovskite films is crucial for fabricating high-performance perovskite solar cells (PSCs). CsPbI 2 Br perovskite, prized for its superb stability toward light soaking and thermal aging, has received a great deal of attention recently. However, the air instability and poor performance of CsPbI 2 Br PSCs are hindering its further progress. Here, an approach is reported for depositing high-quality CsPbI 2 Br films via the Lewis base adducts PbI 2 (DMSO) and PbBr 2 (DMSO) as precursors to slow the crystallization of the perovskite film. This process produces CsPbI 2 Br films with large-scale crystalline grains, flat surfaces, low defects, and long carrier lifetimes. More interestingly, PbI 2 (DMSO) and PbBr 2 (DMSO) adducts could significantly improve the stability of CsPbI 2 Br films in air. Using films prepared by this technique, a power conversion efficiency (PCE) of 14.78% is obtained in CsPbI 2 Br PSCs, which is the highest PCE value reported for CsPbI 2 Br-based PSCs to date. In addition, the PSCs based on DMSO adducts show an extended operational lifetime in air. These excellent performances indicate that preparing high-quality inorganic perovskite films by using DMSO adducts will be a potential method for improving the performance of other inorganic PSCs.

Engineering Halide Perovskite Crystals through Precursor Chemistry

“…As described in Sections and , because of the inadequate complexation between Pb 2+ and I − and the lower solubility of the inorganic component in the perovskite precursor solution, the 1D Lewis adduct of the PbI 2 ·DMF (coordinates with some MAI) would precipitate from the precursor solution prior to perovskite crystallization under an uncontrolled perovskite solidification, leading to the compositional segregation of MAI . Then the PbI 2 ·DMF complex reacts with the segregated MAI to form perovskite crystals with the needle‐like morphology as commonly reported in the literatures . According to classical nucleation theory, shortening the time for the precursor solution to reach the state of supersaturation leads to an increased nucleation rate, which would produce numerous small initial nuclei and give rise to the improved coverage of thin films .…”

Inorganic CsPbI2Br Perovskite Solar Cells: The Progress and Perspective

“…The champion device produces a PCE of 14.81%, which is the highest value among CsPbI 2 Br PSCs to date. More recently, the Lewis base adducts PbX 2 (DMSO) (X = Br, I) have been found to slow the crystallization rate of CsPbI 2 Br and thus improve the film quality . High quality CsPbI 2 Br films showing flat surfaces, large‐scale crystalline grains, long carrier lifetimes (Figure d), and few defects were obtained, resulting in a considerable PCE of 14.78% (Figure e).…”

“…f) J–V curves of devices (FTO/TiO 2 /CsPbI 2 Br/PCBM/Ag) fabricated with and without DMSO adducts. Reproduced with permission . Copyright 2018, Wiley–VCH.…”

Novel Surface Passivation for Stable FA0.85MA0.15PbI3 Perovskite Solar Cells with 21.6% Efficiency

“…Figure e,f shows the typical dark current density–voltage ( J – V ) characteristics of electron‐only devices wo/w TPFPB treatment. The trap densities were estimated by the space charge‐limited current (SCLC) technique . The linear region at low bias corresponds to the ohmic response.…”