Enhanced Photovoltaic Properties of Perovskite Solar Cells by Employing Bathocuproine/Hydrophobic Polymer Films as Hole-Blocking/Electron-Transporting Interfacial Layers.

In this study, chlorodeoxyhydroxyethylcellulose (CDHC) was synthesized from hydroxyethylcellulose (HEC) through chlorination and then both HEC and CDHC were applied individually as additives within the methylammonium lead iodide (CH3NH3PbI3, MAPbI3) layers of perovskite solar cells (PVSCs). The architecture of the PVSCs was indium tin oxide/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/MAPbI3:cellulose derivative/[6,6]-phenyl-C61-butyric acid methyl ester/Ag. The photovoltaic (PV) properties of the HEC- and CDHC-incorporated PVSCs were superior to those of the corresponding pristine PVSC prepared without an additive, a result of decreases in the number of grain boundary defects as well as increases in the crystal grain sizes, crystallinities, and absorption intensities of the modified perovskite films. Moreover, the polymer chains of CDHC, presenting chlorine atoms, were particularly beneficial for enhancing the crystal size and crystallinity of the MAPbI3 film, resulting in the highest absorbance and PV performance in this study being those of a CDHC-doped PVSC. Indeed, this CDHC-incorporated PVSC displayed a short-circuit current density of 17.73 mA cm−2, an open-circuit voltage of 0.96 V, a fill factor of 0.61, and a power conversion efficiency of 10.38%.

Rapid progress has been achieved in perovskite solar cells (PSCs), and their efficiencies have improved from 3.8 % to 24.2 % in less than a decade. With low-cost processing, PSCs have shown exciting photovoltaic (PV) properties, such as effective optical absorption, a long carrier lifetime, and unique defect tolerance. While recent studies demonstrated improved stability up to 100 days, PSC technology is still challenged to meet the stringent industry requirements for commercialization. Despite considerable efforts, the underlying physical mechanisms for the inferior stability of PSCs are not well understood. One reason for this divergence is that many established measurement techniques (e.g., quantum efficiency, photoluminescence) probe the properties on length scales far greater than that of electronic and/or structural inhomogeneity (i.e., < 1 μm near grain boundaries) and therefore characterize convoluted and/or averaged properties. Ion/electron beam-based techniques have been extensively used to access the microstructures of PSCs, enabling atomic/nanoscale structural, chemical, optical, and electrical characterizations. For example, focused ion beam (FIB) milling produces an atomically smooth surface that minimizes the artifacts attributed to the surface roughness. FIB techniques can also create a well-defined cross-section of PSCs without mechanical damage in a physical cleaving sample preparation. While powerful, there are some concerns about possible beam damage of inorganic-organic perovskites via chemical-bond breakage and local heating. This project aims to comprehensively understand how the microstructural/interfacial properties of PSCs (e.g., Methylammonium Lead Iodide [MAPbI₃]) are modified under the irradiating ion beams. Specifically, we investigate the sub-surface properties of PSCs before and after Ar-ion beam injections. Kelvin probe force microscopy (KPFM) measures the contact potential differences (CPDs). Photoluminescence (PL) microscopy in conjunction with Finite-Difference Time-Domain (FDTD) simulations infers the formation of a “dead layer” (< 15 nm) on the subsurface of MAPbI₃ during Ar+ milling processes while preserving the initial bulk properties. The x-ray photoemission spectroscopy (XPS) confirms this modified surface is a lead-rich and iodine-deficient surface. We initiate customizing in-situ measurement setup while measuring the local optical and electrical properties of PSC under thermal (cooling, heating) and light stressors. Our results provide in-depth knowledge of the ion-beam impact on metal-halide perovskites and how this modified sub-surface impacts their properties under accelerated stressors of light and heat. Intensive Monte Carlo simulations of an electron beam interacting with PSCs provide the beam energy distribution in PSCs, proposing possible measurement conditions of using e-beam with minimizing beam damage. Our in-situ measurement platform can accommodate the diverse architecture of PSC devices for studying deterioration mechanisms under mixed environmental stressors.

Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells

In this paper, structural and photovoltaic properties of perovskite CH3NH3PbI3-xClx solar cells added with ammonium iodide (NH4I) are reported. The CH3NH3PbI3-xClx photovoltaic cells were fabricated by a hot air blow-assisted spin-coating method. By addition of NH4I, photovoltaic performance of the CH3NH3PbI3-xClx cell fabricated by the hot air blow-assisted spin-coating method was improved. The microstructure analysis of the resulting cells showed that the NH4I− added CH3NH3PbI3-xClx film was highly oriented along the (100) plane. Moreover, morphological changes of the NH4I− added CH3NH3PbI3-xClx film due to NH4I addition were also observed. The improvements of the photovoltaic performance, the crystal orientation, and the morphological changes of the CH3NH3PbI3-xClx are attributed to NH4I addition.

In this study, we positioned three quaternary ammonium halide-containing cellulose derivatives (PQF, PQCl, PQBr) as interfacial modification layers between the nickel oxide (NiOx) and methylammonium lead iodide (MAPbI3) layers of inverted perovskite solar cells (PVSCs). Inserting PQCl between the NiOx and MAPbI3 layers improved the interfacial contact, promoted the crystal growth, and passivated the interface and crystal defects, thereby resulting in MAPbI3 layers having larger crystal grains, better crystal quality, and lower surface roughness. Accordingly, the photovoltaic (PV) properties of PVSCs fabricated with PQCl-modified NiOx layers were improved when compared with those of the pristine sample. Furthermore, the PV properties of the PQCl-based PVSCs were much better than those of their PQF- and PQBr-based counterparts. A PVSC fabricated with PQCl-modified NiOx (fluorine-doped tin oxide/NiOx/PQCl-0.05/MAPbI3/PC61BM/bathocuproine/Ag) exhibited the best PV performance, with a photoconversion efficiency (PCE) of 14.40%, an open-circuit voltage of 1.06 V, a short-circuit current density of 18.35 mA/cm3, and a fill factor of 74.0%. Moreover, the PV parameters of the PVSC incorporating the PQCl-modified NiOx were further enhanced when blending MAPbI3 with PQCl. We obtained a PCE of 16.53% for this MAPbI3:PQCl-based PVSC. This PQCl-based PVSC retained 80% of its initial PCE after 900 h of storage under ambient conditions (30 °C; 60% relative humidity).

Despite the many promising properties of perovskite solar cells (PSCs), ultraviolet (UV)‐induced degradation remains a critical issue for their long‐term reliability. One potential solution is the selective inhibition of UV exposure before it reaches the PSCs; however, this approach leads to a reduction in PSC efficiency due to limited photon utilization. In this regard, here a universally applicable method is presented to address the UV stability issue of PSCs without compromising their high‐level efficiency while also providing device flexibility. A UV‐absorbing colorless polyimide (CPI) substrate serves as a flexible protective shield against UV illumination. The photocurrent loss in CPI‐based PSCs is mitigated by a nanostructured photonic sticker that incorporates a UV‐to‐visible downshifting medium, which can be easily integrated with the fabricated PSC substrate. Through the combined effects of downshifting and synergistic light trapping, the efficiency of UV‐resistant CPI‐based PSCs is improved from 18.6% to 20.4%, making it comparable to the performance of UV‐damageable glass‐based PSCs. Together with numerical modeling, various experimental characterizations of optical and photovoltaic properties, as well as stability assessments under UV, bending, and off‐normal incidence conditions, provide insights into the underlying physical phenomena and optimal design considerations for successful application.

Abstract: Thickness of ETL (Electron transport layer) shows important role in term of stability and efficiency of perovskite solar cells. In this paper the numerical simulation and extensive modeling have been performed on perovskite solar cell using perovskite material such as methyl ammonium lead Iodide (MAPbI3, MA=CH3NH3) with the help of SCAPS tool. The electrical properties of the MAPbI3 material used as active layer, have been calculated for different parameter such as open-circuit voltage (Voc), fill factor (FF), the power conversion efficiency (PCE), and short-circuit current density (Jsc) respectively. Capacitance-frequency (C-f) and capacitance-voltage (C-V) characteristics have been calculated for CH3NH3PbI3 perovskite solar cell. The inorganic copper iodide (CuI) material perform as the hole transport layer (HTL) in simulated structure of the perovskite solar cell. The simulation result shows that increasing the thickness of ETL decreasing the efficiency of perovskite solar cell. Keywords: Perovskite solar cell, CH3NH3PbI3, CuI, Thickness, FF, Voc, Jsc, PCE, C-f and C-V Cite this Article Ravi Shankar Yadav, Major G.S. Tripathi, Bramha P. Pandey. Effect of ETL layer thickness on perovskite (CH3NH3PbI3) solar cell. Trends in Opto-Electro & Optical Communication. 2019; 9(1): 32–37p.

Properties of electron transporting layer (ETL) play an important role on photovoltaic performances of perovskite solar cells. In this work, effects of Sn incorporation on properties of ZnO-based perovskite solar cells were investigated. Sn-doped ZnO (TZO) thin film as ETL was prepared via a sol–gel method. With 5% atom doping, TZO film coated on an indium doped tin oxide (ITO) substrate provided comparable light transmittance with that of an undoped ZnO/ITO substrate. It was also found that the optical band gap of TZO film (3.30 eV) is slightly wider than that of the ZnO one (3.28 eV). These results suggest that Sn atoms probably incorporated into the ZnO crystal during the sol-gel method. The grains size of perovskite layer coated on TZO or ZnO films also showed variation. The perovskite crystal on the TZO thin film (average 300 nm) was larger than that of the one on ZnO thin film (average 277 nm). The preliminary results indicate that the perovskite solar cell based on TZO film provided higher power conversion efficiency (PCE) of 4.42 % than the ZnO-based device (3.16%). Short-circuit current density (Jsc), open-circuit voltage (Voc) and fill factor (FF) of TZO-based device were also higher than the ZnO-based device. This may be because TZO film may provide lower resistivity and better ETL/perovskite interface contact, confirmed by lower series resistance and higher shunt resistance of the TZO-based device. Finally, this work introduced a simple method to prepare TZO film at low temperature for photovoltaic application. It may help guide the development of flexible solar cells and other optoelectronic devices.

A bathocuproine (BCP) layer is typically used as the hole-blocking layer in p-i-n-structure perovskite solar cells (PSCs) between PC61BM and Ag electrodes. Before evaporating the Ag, we used a low-temperature (<40 °C) atmospheric-pressure dielectric barrier discharge jet (DBDjet) to treat the BCP with different scan rates. The main purpose of this was to change the contact resistance between the BCP layer and the Ag electrodes through surface modification using a DBDjet. The best power conversion efficiency (PCE) of 13.11% was achieved at a DBDjet scan rate of 2 cm/s. The He DBDjet treatment introduced nitrogen to form C−N bonds and create pits on the BCP layer. This deteriorated the interface between the BCP and the follow-up deposited-Ag top electrode. Compared to the device without the plasma treatment on the BCP layer, the He DBDjet treatment on the BCP layer reduced photocurrent hysteresis but deteriorated the fill factor and the efficiency of the PSCs.

In this study, three fullerene derivatives─C60tBu, C60TPY, and C60TPY-Cl─were synthesized and investigated as additives in PC61BM-based electron-transporting layers (ETLs) for inverted perovskite solar cells (PVSCs). The incorporation of C60tBu and C60TPY into the ETLs led to improved ETL morphology and passivation of crystal defects on the surface of the methylammonium lead iodide (MAPbI3) layer. This defect passivation enhanced crystal quality, increased UV-vis absorption, reduced charge recombination, and improved electron mobility in the C60tBu- and C60TPY-based PVSCs. The passivation effect of C60TPY, which contains a 2,2':6',2″-terpyridine (TPY) unit, was found to be superior to that of C60tBu, which features a t-butyl ester group. As a result, PVSCs utilizing C60TPY exhibited enhanced photovoltaic performance compared to those incorporating C60tBu. To further investigate the contribution of the TPY moiety to the passivation effect, C60TPY was neutralized with HCl to afford C60TPY-Cl. As anticipated, the protonation of the TPY group in C60TPY-Cl resulted in poorer ETL morphology and diminished defect passivation within the MAPbI3 layer. Consequently, no improvement in photovoltaic properties was observed for PVSCs treated with C60TPY-Cl. The architecture of the inverted PVSCs doped with fullerene derivatives consisted of indium tin oxide/NiOx/MAPbI3/fullerene derivative: PC61BM/bathocuproine/Ag. Among the fullerene-based additives, C60TPY demonstrated the highest photovoltaic performance, achieving a power conversion efficiency (PCE) of 20.10%, an open-circuit voltage of 1.07 V, a short-circuit current density of 24.85 mA cm-2, and a fill factor of 75.6%. Furthermore, the C60TPY-based PVSC retained 80% of its initial PCE after 450 h of storage under ambient conditions (30 °C, 40% relative humidity).

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

Maximizing photovoltaic performance of all-inorganic perovskite CsSnI3-xBrx solar cells through bandgap grading and material design

Analysis of electrical parameters of p-i-n perovskites solar cells during passivation via N-doped graphene quantum dots

Lead-free tin perovskite solar cells

Shallow Iodine Defects Accelerate the Degradation of α-Phase Formamidinium Perovskite