Exploring Inorganic Binary Alkaline Halide to Passivate Defects in Low‐Temperature‐Processed Planar‐Structure Hybrid Perovskite Solar Cells

Abstract

Planar perovskite solar cells obtained by low‐temperature solution processing are of great promise, given a high compatibility with flexible substrates and perovskite‐based tandem devices, whilst benefitting from relatively simple manufacturing methods. However, ionic defects at surfaces usually cause detrimental carrier recombination, which links to one of dominant losses in device performance, slow transient responses, and notorious hysteresis. Here, it is shown that several different types of ionic defects can be simultaneously passivated by simple inorganic binary alkaline halide salts with their cations and anions. Compared to previous literature reports, this work demonstrates a promising passivation technology for perovskite solar cells. The efficient defect passivation significantly suppresses the recombination at the SnO2/perovskite interface, contributing to an increase in the open‐circuit voltage, the fast response of steady‐state efficiency, and the elimination of hysteresis. By this strong leveraging of multiple‐element passivation, low‐temperature‐processed, planar‐structured perovskite solar cells of 20.5% efficiencies, having negligible hysteresis, are obtained. Moreover, this defect‐passivation enhances the stability of solar cells with efficiency beyond 20%, retaining 90% of their initial performance after 30 d. This approach aims at developing the concept of defect engineering, which can be expanded to multiple‐element passivation from monoelement counterparts using simple and low‐cost inorganic materials.

High‐Quality Sequential‐Vapor‐Deposited Cs2AgBiBr6 Thin Films for Lead‐Free Perovskite Solar Cells

“…An average PCE of 0.99% from 68 cells is achieved (Figure S7b, Supporting Information). The J – V curves of our devices show a hysteresis under forward and backward scanning direction (Figure S7a, Supporting Information) that can be attributed to the non‐optimized charge extraction interfaces as demonstrated by recent reports . The corresponding maximum power point output performance is shown in Figure b.…”

Review of Novel Passivation Techniques for Efficient and Stable Perovskite Solar Cells

“…Recently, high performing perovskite devices have increased compositional complexity by incorporating Group 1 (alkali metals) elements such as Na, K, or Cs. These materials have also been adopted as a dopant or an additional layer on ETLs for alleviating trap states at the ETL/perovskite interface . Seo et al reported a modification of the TiO 2 surface by CsBr to strengthen its interaction with the perovskite for rapid extraction of photogenerated electrons which lead to very high fill factor close to 80% from their cells.…”

“…Such cell has V oc of 1.14 V and PCE up to 21% with negligible hysteresis. Liu et al deposited KCl layer on the c‐TiO 2 layer and confirmed that TiO 2 /perovskite interfacial recombination was suppressed, resulting in an increase of V oc (1.13 V) and the elimination of hysteresis.…”

High‐Performance Flexible Perovskite Solar Cells with Effective Interfacial Optimization Processed at Low Temperatures

“…Figure 5a indicates that the PL was quenchedb ecause of fast electron transfer to ETLs, indicatingt hat more electron holes were transported from the perovskite layer to the perovskite/ETL interface. [24,32] The ammonium cation, the radiuso fw hich is close to Rb, [15] tends to combine with perovskite film and passivate positive ion vacancies. Previous studies have shown that Cl À in the interface has no significant contribution to the blueshift of the perovskite peak, confirming that NH 4 + effectively passivates trap-states of the perovskite absorber film.…”