Understanding the effects of annealing temperature on the mechanical properties of layers in FAI-rich perovskite solar cells

O V Oyelade,Y A Olanrewaju,K Orisekeh,R Koech,R Ichwani,R A Ahmed,J Cromwell,S A Adeniji,D M Sanni,W O Soboyejo,V C Anye,D O Oyewole,O K Oyewole

doi:10.1063/5.0078558

Abstract

This paper uses a combination of experiments and theory to study the effects of annealing temperature on the mechanical properties of hybrid organic–inorganic perovskites (HOIPs). We examined the mechanical (hardness and Young’s modulus), microstructural, and surface topography properties of the HOIP film at different annealing temperatures ranging from 80 to 170 °C. A mechanism-based strain gradient (MSG) theory is used to explain indentation size effects in films at different annealing temperatures. Intrinsic film yield strengths and hardness values (deduced from the MSG theory) are then shown to exhibit a Hall–Petch dependence on the inverse square root of the average grain size. The implications of the results are then discussed for the design of mechanically robust perovskite solar cells.

Highlights

IntroductionHybrid organic–inorganic perovskites (HOIPs) have emerged as promising energy-related materials for light absorbers in PV cells and emitters in light-emitting diodes (LEDs) and photodetectors. a=nCdHX3N=HI−3+1,(BTMrh−Ae1+,g)oe,rnCeCHrla−(lN1.fHoTr2hm)e2+uelf(afFicAoife+n)H,cyoOroICPf ssp+ei;rsBoAv=sBkPXitbe3+, s2owolharreSrcnee2l+Als;(PSCs) has increased drastically above 25%4 over the past decade due to the novel electronic and optical, thermoelectric, and surface properties of the perovskite absorbers; scalable properties; low processing-temperature; tunable and direct bandgaps; and high extinction coefficients, high carrier mobility, low exciton binding energies, and high absorption over a wide range of wavelengths. Perovskite materials have potential for wearable functional devices with great mechanical flexibility and robustness. With the growing interest in HOIPs for deformable devices, the knowledge of their mechanical response to dynamic strain can adequately implement these materials on flexible and stretchable devices
Lead iodide (PbI2)(99.999%), di-isopropoxide bis(acetylacetone), formamidinium iodide (FAI) (98%), methylammonium chloride (MACl), methylammonium bromide (MABr) (98%), dimethyformamide (DMF), dimethylsulfoxide (DMSO), titania paste, 1-butanol, ethanol, iso-propyl alcohol (IPA), 4-tert-butylpyridine, acetonitrile, lithium bis(trifluoromethylsulfonyl) imide (LiTFSI), 2, 2′, 7,7′-tetraksi (N,N-di-p-methoxyphenylamine)-9,9′ -spirobifluorene (Spiro-OMeTAD), and anhydrous chlorobenzene were all purchased from Sigma-Aldrich (Natick, MA, USA)
We estimated the grain size values from scanning electron microscope (SEM) images of several perovskite films that were processed at different annealing temperatures

Summary

Introduction

Hybrid organic–inorganic perovskites (HOIPs) have emerged as promising energy-related materials for light absorbers in PV cells and emitters in light-emitting diodes (LEDs) and photodetectors. a=nCdHX3N=HI−3+1,(BTMrh−Ae1+,g)oe,rnCeCHrla−(lN1.fHoTr2hm)e2+uelf(afFicAoife+n)H,cyoOroICPf ssp+ei;rsBoAv=sBkPXitbe3+, s2owolharreSrcnee2l+Als;(PSCs) has increased drastically above 25%4 over the past decade due to the novel electronic and optical, thermoelectric, and surface properties of the perovskite absorbers; scalable properties; low processing-temperature; tunable and direct bandgaps; and high extinction coefficients, high carrier mobility, low exciton binding energies, and high absorption over a wide range of wavelengths. Perovskite materials have potential for wearable functional devices with great mechanical flexibility and robustness. With the growing interest in HOIPs for deformable devices, the knowledge of their mechanical response to dynamic strain can adequately implement these materials on flexible and stretchable devices. Hybrid organic–inorganic perovskites (HOIPs) have emerged as promising energy-related materials for light absorbers in PV cells and emitters in light-emitting diodes (LEDs) and photodetectors. a=nCdHX3N=HI−3+1,. (PSCs) has increased drastically above 25%4 over the past decade due to the novel electronic and optical, thermoelectric, and surface properties of the perovskite absorbers; scalable properties; low processing-temperature; tunable and direct bandgaps; and high extinction coefficients, high carrier mobility, low exciton binding energies, and high absorption over a wide range of wavelengths.. Perovskite materials have potential for wearable functional devices with great mechanical flexibility and robustness.. The understanding of variations in the mechanical properties of HOIP structures that are processed at different annealing scitation.org/journal/adv conditions is critical for ultimate device performance and robustness. Annealing temperature influences the structure, morphology, crystallinity, and optoelectrical properties of perovskite films.. The annealing process is critical in the formation of the perovskite film and, in the power conversion efficiency (PCE) of the assembled devices.. Annealing temperature influences the structure, morphology, crystallinity, and optoelectrical properties of perovskite films. The annealing process is critical in the formation of the perovskite film and, in the power conversion efficiency (PCE) of the assembled devices. Increased annealing temperature can cause inter-diffusion and increased local stresses that can lead to the nucleation of cracks and pinhole formation

Methods

Results

Conclusion