The lifespan of perovskite solar cells (PSCs) is considered a critical factor. Due to the presence of organic components, perovskite films are prone to irreversible phase transitions or rapid decomposition into PbI₂ under high temperature, high humidity, and high oxygen conditions. While external physical encapsulation can significantly improve the stability and lifespan of PSC devices by preventing the intrusion of water vapor in natural environments, the inherent stability of perovskite films remains a limiting factor. Residual stress generated during high-temperature annealing and cooling is an undeniable factor contributing to the inherently poor stability of perovskite films. To address these issues, Yang Junliang's research group at Central South University proposed a surface microetching and reconstruction strategy to regulate stress in trication perovskite films.

The optimized PSC device achieved a PCE of 25.54% at an open-circuit voltage (Voc) of 1.2V. Unencapsulated devices maintained over 90% of their initial efficiency after 40 days of storage at 20% relative humidity and 83% of their original performance during MPP tracking under continuous nitrogen illumination. Furthermore, for a mini-module with an area of 10.4 cm², the PCE reached 21.02%. This research provides a new approach for surface micro-etching and reconstruction to effectively modulate residual stress on perovskite films.

Figure 1.a)Schematic diagrams of conventional in-situ formation of 2D perovskite and microetching and reconstruction process on the surface of perovskite film using LA/IPA mixed solution. Top-view SEM images of (b)control, (c)LA/IPA, (d)OAI and (e) LA/IPA-15/OAI treated perovskite films. AFM images of (f) control, (g)LA/IPA, (h) OAI and (i) LA/IPA-15/OAI treated perovskite films.

Figure 2. a), b) Transmission FTIR spectra of pure LA and LA+FAI solutions. c) The proportion (atomic ratio, and weight ratio) of surface Pb content of different films obtained from X-ray photoelectron spectroscopy (XPS) spectra. d) XRD pattern of different perovskite films. e) A small range of XRD patterns of OAI, LA/IPA-10/OAI, LA/IPA-15/OAI and LA/IPA-20/OAI treated perovskite films. f) Tauc plots of the control, OAI, and LA/IPA-15/OAI treated perovskite films. g) and h) UPS spectra of different perovskite films. i) Schematic diagram of the energy level structure of films with different treatment methods.

Figure 3. GIXRD patterns of a) control, b) OAI-treated and c) LA/IPA-15/OAI-treated perovskite films. d) Linear fit of 2θ-sin2ψ for perovskite films. e) Schematic diagram of residual stress on the surface of ideal, control, OAI-treated and LA/IPA-15/OAI-treated perovskite films (from left to right).

Figure 4. a) Steady-state PL and b) TRPL analysis of the control and LA/IPA-15/OAI treated perovskite films. c) Light intensity dependence on Voc for the different devices. d) EIS spectra of control and LA/IPA-15/OAI modified devices under the dark conditions. Insert is equivalent circuit diagram.

Source of this article DOI:10.1039/d4ee04248d

https://pubs.rsc.org/en/content/articlelanding/2024/ee/d4ee04248d