Search

The design of electron transport layers (ETLs) with good optoelectronic properties is one of the keys to the improvement of the power conversion efficiencies (PCEs) and stability of perovskite solar cells (PSCs). Titanium dioxide (TiO2), one of the most widely used ETL in PSCs, is characterized by low electrical conductivity that increases the series resistance of PSCs, thus limiting their PCEs. In this work, we incorporated tin oxide (SnO2) into titanium dioxide (TiO2) and studied the evolution of its microstructural and optoelectronic properties with SnO2 loading. The thin films were then integrated as ETLs in a regular planar Formamidinium (FA)-rich mixed lead halide PSCs so as to assess the overall effect of SnO2 incorporation on their charge transport and Photovoltaic (PV) characteristics. Analysis of the fabricated PSCs devices revealed that the best performing devices; based on the ETL modified with 0.2 proportion of SnO2; had an average PCE of 17.35 ± 1.39%, which was about 7.16% higher than those with pristine TiO2 as ETL. The improvement in the PCE of the PSC devices with 0.2 SnO2 content in the ETL was attributed to the improved electron extraction and transport ability as revealed by the Time Resolved Photoluminescence (TRPL) and Electrochemical Impedance Spectroscopy (EIS) studies.

One route to a brighter global energy future may be through enhancing the efficiency and stability of perovskite solar cells (PSCs), which depends on the level of defects in the photoactive absorber and along the interfaces of the multilayered structure. Here, we use a combined experimental and theoretical approach to study the effects of pressure-induced compaction of microvoids and closure of cracks on the power conversion efficiency (PCEs) and stability of formamidinium-rich PSCs. A range of mechanical pressures was applied to the PSCs to reduce pre-existing grain-boundary voids and interfacial cracks within the devices. The PCEs of the PSCs increased from ~19.5% to ~ 23.5% for applied pressures between ~ (0 – 7) MPa. Unlaminated device stability increased by 33%, falling to 80% of initial PCE in 1800 hrs without compression, as compared to 2400 hrs with compression. The implications of this study are discussed in light of possible future manufacturing processes.

This paper presents the results of a combined experimental and analytical/computational study of the effects of pressure on photoconversion efficiencies of perovskite solar cells (PSCs). First, an analytical model is used to predict the effects of pressure on interfacial contact in the multilayered structures of PSCs. The PSCs are then fabricated before applying a range of pressures to the devices to improve their interfacial surface contacts. The results show that the photoconversion efficiencies of PSCs increase by ~40%, for applied pressures between 0 and ~7 MPa. However, the photoconversion efficiencies decrease with increasing pressure beyond ~7 MPa. The implications of the results are discussed for the fabrication of efficient PSCs.

The interfacial robustness of perovskite solar cells (PSCs) is important due to the potential for failure resulting from applied loads or deformation in devices that are fabricated on rigid or flexible substrates, and/or residual stresses due to thermal expansion mismatch between layers. Since these can occur across any of the interfaces within typical hybrid organic–inorganic perovskite solar cells, we explore the mechanisms of interfacial fracture between the layered structures of model hybrid organic–inorganic perovskite solar cells. Brazil disk interfacial fracture specimens enable studies of the mode-mixity dependence of interfacial fracture toughness for each interface. The robustness of interfaces is studied across a range of mode mixities between pure mode I and pure mode II. A combination of optical and scanning electron microscopy further elucidates the underlying crack/microstructure interactions and fracture modes. These reveal crack-tip shielding due to crack bridging and microcracking, which were modeled using a zone shielding model to predict the mode-mixity dependence of the interfacial fracture toughness values. We discuss the implications for the development of hybrid organic–inorganic perovskite solar cells with robust interfaces for scalable deployment of photovoltaics.

The effort to enhance the visible-light photoresponse of SnO2 and SnO has been designed by the heterostructure formation of tin oxide. The formation was conducted by controlling the oxidation state of precursor through adjusting the precursor acidity. The result shows that the transformation route as a function of precursor initial pH involve the formation of intermediate phase began by SnO2 to SnO2/Sn3O4 to SnO/Sn3O4, and finally SnO. The characterization indicated that Sn3O4 played the important role in enhancing the visible light response of both SnO2 and SnO in the heterostructure formation.

Incorporation of cesium (Cs) into the perovskite layer has become a good strategy to boost the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, a suitable and scalable method of Cs incorporation in a perovskite film that does not cause a significant increase in the optical bandgap is needed. In this paper, we introduce a thin layer of CsBr into a formamidinium (FA)-rich mixed halide perovskite film using the thermal evaporation technique. The effects of the thickness of the CsBr layer on the microstructural, structural, and optoelectronic properties and surface chemical states of the perovskite film are then studied. The results indicate that the CsBr layer thickness is able to tune the microstructural and optoelectronic properties of the perovskite film. Planar PSCs fabricated with different thicknesses of CsBr layers in the perovskite absorber exhibited different photovoltaic performance characteristics. The CsBr-modified PSC device with a 50 nm layer of CsBr in the perovskite layer showed a better PCE of 16.19% ± 0.17%, which was about 15% higher than that of the control device, and was able to retain nearly 70% of its initial PCE value after 120 days of storage in an unencapsulated state.

Annealing is one of the processing methods that are used for the fabrication of defect-free, photoactive perovskite films with compact grains in highly efficient and stable perovskite solar cells (PSCs). Thus, the annealing temperature is a key parameter for the control of the interdiffusion (of constituent elements) in photoactive films. In this paper, we present the results of a systematic study of the effects of annealing on the interdiffusion of constituent elements in efficient formamidinium-based PSCs. We also explore the effects of annealing-induced interdiffusion on layer microstructures, local strains, and the optoelectronic properties of perovskite films. We observe a dramatic upward diffusion of tin (Sn) and titanium (Ti) from fluorine-doped tin oxide and titanium dioxide (TiO2) to the perovskite films. We also observe a downward diffusion of lead (Pb) and iodine (I) from the perovskite films to the mesoporous layer of the electron transporting layer (ETL), after annealing at temperatures between 100 and 150 °C. The diffused I substitutes for Ti in the ETL, which improves the optoelectronic properties of the films, for annealing temperatures between 100 and 130 °C. The annealing-induced interdiffusion that occurs at higher temperatures (between 140 and 150 °C) results in higher levels of interdiffusion, along with increased local strains that lead to the nucleation of pores and cracks. Finally, the implications of the results are discussed for the design of PSCs with improved photoconversion efficiencies and stability.

Thin film solar cell technology is currently facing challenges related to improvement in the performance parameters such as efficiency, fill factor, etc. primarily linked with poor heterojunction interface formation, and the use of toxic materials. CdTe/CIGS and CdS dominate the TFSC industry as the typical absorber and buffer layer materials. The expensive and hazardous nature of these materials, and their fabrication method demands for proper alternatives with potential for similar or better performance. Recent findings indicated the potential of using Cu 2 ZnSnS 4 (CZTS) and In 2 S 3 as the absorber and buffer layers respectively. Several publications focus upon synthesizing CZTS and In 2 S 3 films using solution deposition techniques (electrodeposition, chemical spray pyrolysis, etc.) and characterizing materials to study the impact of various deposition parameters. However, limited work has been performed on synthesizing both materials to form a heterojunction device for solar cell applications using one particular method. The presented work illustrates electrochemical synthesis of p-CZTS/n-In 2 S 3 based photovoltaic device using a basic three-electrode electrochemical cell-setup. The experimental results reveal good stoichiometry, crystalline structure, and morphology for In 2 S 3 and CZTS films to eventually fabricate a desired heterojunction device.