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The electron transport layer (ETL) is essential for electron collection from the absorbing layer to the conductive electrode in solar cell devices, such as perovskite solar cells. Zinc oxide (ZnO) is regarded as a promising ETL material thanks to its wide bandgap and high electron mobility. In this study, multiple-layer ZnO thin films were elaborated using inkjet printing and investigated using X-ray diffraction, Fourier transform infrared spectroscopy, spectrophotometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrical measurements. All samples show a characteristic infrared vibration of Zn–O bonding and a hexagonal wurtzite crystalline phase. Moreover, the deposited films exhibit preferential growth directions, with a highly textured ZnO film along the (100) orientation after 8-layer inkjet printing. The ZnO films also show a direct bandgap with a stable energy of 3.25 ± 0.02 eV and strong visible light transmittance, with a moderate decrease as the number of inkjet-printed layers increases. The variations in film electrical resistivity result from competing structural and electron scattering mechanisms and present the lowest value of about 9 × 103 Ω cm for the 8-layer ZnO film. Our work underlines the successful elaboration of ZnO thin films by inkjet printing and sets the stage for further studies about other inkjet-printed materials of interest for solar cell technology. • Zinc oxide films are elaborated at room temperature by multiple-layer inkjet printing. • Multilayer films show a ZnO wurtzite phase and crystallographically textured growth. • ZnO films exhibit high visible light transmittance and a stable and direct bandgap. • Phase changes and electron scattering modes affect electrical resistivity of films. • Inkjet-printed ZnO is promising for electron transport in perovskite solar cells. [ABSTRACT FROM AUTHOR]

Aiming to enhance the properties of gallium doped zinc oxide (GZO) for considering it as a promising electron transport layer (ETL) in perovskite solar cells (PSCs), GZO thin films were sputtered using radio frequency (RF) magnetron sputtering under different Ar gas flow from 2 sccm to 5 sccm. Then the variations of morphological, structural, optical and electrical properties of the GZO thin films were studied thoroughly. The sputtered GZO films showed polycrystallinity having a hexagonal wurtzite-type crystal structure with a preferred crystal orientation in the direction of (0 0 2). In terms of morphological analysis, EDX confirmed the presence of Ga and FESEM analysis revealed that the thickness and grain size of deposited films gradually increase with the increment of Ar flow. Further, the film deposited at 3 sccm showed the lowest electrical resistivity of 1.09 × 10−02 Ω-cm and achieved the highest carrier concentration of 1.586 × 1019 cm−3. All the GZO films showed optical transmittances between ∼80 % and ∼90 %. Finally, the simulation study validated the use of sputtered GZO as ETL in PSCs. This study provides a significant path for the researchers to optimize the RF-sputtered GZO films by varying the Ar gas flow rate for confirming their use as promising ETL in PSCs. • Effect of Ar gas flow on the RF sputtered GZO film properties. • Lower Ar flow produces films with higher optical transmittance. • Energy bandgap reduces with the increment of Ar gas flow rate. • Higher Ar gas flow produces films with higher grain size and thickness. • RF sputtered GZO as ETL in pesrovskite solar cells through SCAPS-1D. [ABSTRACT FROM AUTHOR]

The new generation of solar cell technology, perovskite solar cells (PSCs), are the most promising candidates to meet global energy demands. In the current study, we improved the efficiency of their cost-effective type, i.e., carbon-based PSCs, by employing an interface engineering on the tin dioxide (SnO 2) electron transport layer (ETL). A fluorine doped-zinc oxide material was used to treat the SnO 2 layer and prepare a better substrate for perovskite fabrication. The fabricated perovskite layer on the treated SnO 2 reveals better charge transfer, lower charge recombination, and lower leakage current. In addition, the fabricated perovskite layer on the modified ETL showed improved crystalline properties with passivated grain boundaries. As a result, a champion efficiency of 15.22% was recorded for the target carbon-based PSCs, referring to improved photovoltaic performance. Notably, the target devices showed a higher stability behavior against ambient air and kept 95% of their initial efficiency after 1658 h ageing time. • Developed an interface engineering technique utilizing fluorine-doped zinc oxide to enhance the efficiency of carbon-based perovskite solar cells (PSCs). • Achieved a champion efficiency of 15.22% for the PSCs, showcasing improved photovoltaic performance through better charge transfer, reduced recombination, and lower leakage current. • Demonstrated exceptional stability against ambient air, with the target devices maintaining 95% of their initial efficiency after 1658 h of aging time. [ABSTRACT FROM AUTHOR]

Lead-free perovskite solar cells (PVSC) are emerging as a very relevant research topic in the modern environment era, where toxicity and stability are the two most significant hurdles for lead-based PVSC design. Existing lead-free perovskites suffer from the same inefficiency problems. The focus of this research is the development and analysis via SCAPS-1D simulator of Pb-free design of CsSn 0.5 Ge 0.5 I 3 /FASnI 3 based PVSC. A numerical modelling programming tool is used to examine the influence of many critical parameters on device efficacy. These parameters include the decision of the optimal hole transport layer (HTL), optimal electron transport layer (ETL), doping density, the optimized thickness of both absorber layers, defect density, and interface defect density between numerous films. The highest power conversion efficiency (PCE) of 31.58%, short circuit current density (J sc) of 29.239 mA/cm2, open-circuit voltage (V oc) of 1.202 V, and fill factor (FF) of 89.55% are all achieved by the optimized device architecture with MoS 2 as the HTL and IGZO as the ETL. This demonstrates that high-performance lead-free PVSC can be achieved experimentally by further optimization of the device characteristics. [ABSTRACT FROM AUTHOR]

This work reports on the synthesis of polymeric PANI-rGO-WS 2 (PGW) nanocomposites were synthesized with varying concentrations of WS 2 via chemical oxidative polymerization. FESEM images elucidated that the surface morphology of PGW3 carried a structure comprising of PANI nanofibers embedded on the top of the overlapped rGO and WS 2 nanosheets. XRD and FTIR spectroscopy showed the molecular interaction among the constituents and affirmed the formation of PGW nanocomposite. UV–Vis. spectroscopy revealed the absorption of light in visible region with the for PGW3 nanocomposite. Photoluminescence spectroscopy showed light absorption in blue color region with excellent color purity. TGA showed the optimized PGW3 nanocomposite has inflated thermal stability. Current density for PGW3 nanocomposite was examined using J-V characteristic curve and found 96% higher than polyaniline. The increased conductivity and high electron-hole recombination rate attributed to the formation of enhanced charge transport network in PGW3 nanocomposite. These results evinced the optimized PGW3 nanocomposite as an ETL for OLED applications. • In-situ oxidative polymerization method is used to synthesize PANI-rGO-WS 2 nanocomposites with varying concentration of WS 2. • The band gap of optimized PGW3 nanocomposite is determined to be 1.95 eV with a crystallite size of 6.54 nm. • PGW3 nanocomposite showed blue emission at 483 nm range with 39% color purity. • The mobility of charge carriers was also calculated using hall effect measurement and found to be 2.707 m2V−1s−1 • The current density for the optimized PGW3 was evaluated ∼3.45 Acm−2 using J-V characteristic curve. [ABSTRACT FROM AUTHOR]

Hybrid perovskite solar cells (PSCs) have introduced as a good revolution photovoltaic to meet the green world energy demands. The crystallinity improvement of PSCs is a practical approach to improve the efficacy of PSCs. Double cation formamidinium (FA)/methylammonium (MA) PSCs were fabricated by using a simple sequential deposition process. The mesoporous titanium dioxide (TiO 2) layers with 200 nm thickness were used as the electron transport layer (ETL). It was observed that with changing the FA/MA precursor temperature could achieve more desirable perovskite films for photovoltaic applications. Our measurements show that with pre-heating of FA/MA solution at 55 °C the defects on the perovskite layer are well passivated. Besides, the perovskite with better crystallinity and smooth morphology, and the defect-free surface was achieved. It is delightful that perovskite with 55 °C reveals stronger photon absorption and better charge collection. Using the pre-heating approach, a redshift in edge absorption of the perovskite films was observed, indicating a better light-harvesting phenomenon in the corresponding perovskite films. Through optimization of the pre-heating temperature of FA/MA solution, a champion PCE of 13.77% was yielded for PSCs higher than of 10.05% one for pre-heating. Also, modified mixed cation devices revealed higher stability behavior in atmospheric conditions than the reference devices. Image 1 • The optoelectrical properties of mixed cation perovskite are modified using different FA/MA solution temperature. • This modification results in enhancing of the average device power conversion efficiency reaching to 13.7%. • The enhancement in performance originates from improved perovskite film formation and more efficient charge extraction. [ABSTRACT FROM AUTHOR]

Two perovskite solar cells one with leaves and needles like TiO 2 (LNT) and other with meso-porous TiO 2 as electron transfer layer (ETL) were fabricated. The perovskite solar cell structure FTO/Compact-TiO 2 /LNT/CH 3 NH 3 PbBr 3 /Spiro-OMeTAD/Ag with leaves and needles like TiO 2 electron collector, exhibit high efficiency up to 9% being supported by high open-circuit voltage and fill factor up to 0.8 V and 0.89, respectively. The second perovskite solar cell structure FTO/Compact-TiO 2 /Meso-porous TiO 2 /CH 3 NH 3 PbBr 3 /Spiro-OMeTAD/Ag with meso-porous TiO 2 electron collector, efficiency is 6.2% with open-circuit voltage and fill factor up to 0.77 V and 0.71 respectively. As compared to meso-porous TiO 2 electron collector layer, leaves and needles like TiO 2 has better electron band alignment with compact TiO 2 as hole blocking layer and hence, results in higher efficiency. Image 1 • A novel architecture of Perosvkite solar cell has been proposed. • A new leaves and needles like structure of TiO 2 has been grown using simple technique. • Application of leaves and needles like structures of TiO 2 has been demonstrated as an electron transport layer. • Power conversion efficiency of 9% for the proposed solar cell has been achieved. [ABSTRACT FROM AUTHOR]

The performance of a perovskite solar cell (PSC) is improved with a graphene electron transport layer (ETL) using Silvaco simulation software. Factors affecting solar cell performance such as absorber layer thickness, carrier mobility, doping concentration and carrier transport layer thickness have been studied. Higher carrier mobility, and fabrication cost are the most important factors toward the increment of the PSC utilization. Graphene is used here as an ETL due to its high carrier mobility, high optical transparency and good optical, mechanical and electrical properties at a low cost. The simulation is based on glass/ITO/Graphene/CH 3 NH 3 PbI 3 /Spiro-OMeTAD/Au structure which yields to photovoltaic (PV) parameters of V oc = 1.094 V, J sc = 21.24 mA/cm2, FF = 90.185%, and power conversion efficiency of 20.95%. Moreover, the optimum thicknesses of 600 nm and 21 nm are determined for the perovskite absorber and ETL, respectively. • Graphene is employed as the ETL in PSC structure. • An optimum structure is obtained considering thickness and doping concentration variations. • The maximum PCE of 20.95% is achieved. [ABSTRACT FROM AUTHOR]

An organic-inorganic perovskite formamidinium tin iodide (HC(NH 2) 2 SnI 3 – FASnI 3) is used as light absorbing layer in photovoltaics due to its lead-free nature, wider bandgap of 1.41 eV and better temperature stability than CH 3 NH 3 SnI 3. In the present investigations, SCAPS simulation with comparison to the experimental as well as simulation data for FASnI 3 -based solar cell device is accomplished for high power conversion efficiency with proper optimization. The variation in the device design key parameters such as absorber, hole transport layer and electron transport layer thickness including defect density, doping concentration in absorber, carriers capture cross sections and interfacial defects are examined with their impact on device performance. The preliminary structure of device is based on the reported experimental and simulation work with the efficiency of 1.75% and 1.66%, respectively. After the SCAPS simulation with the optimization of basic parameters in this work, the final optimized performance parameters of the solar cell device are found to be enhanced with short-circuit current density (J sc) of 31.20 mA/cm2, open-circuit voltage (V oc) of 1.81 V, fill factor (%FF) of 33.72% and power conversion efficiency (%PCE) of 19.08%. Image 1 • Physics behind the performance parameters in (HC(NH 2) 2 SnI 3 – FASnI 3) PSC device. • Comparison FASnI 3 -based PSC performance with reported experimental and SCAPS simulation results. • Study the effect on the device with the variation of basic parameters of cell. • Final optimized parameters achieved: J sc -31.20 mA/cm2, V oc -1.81 V, FF-33.72% and PCE-19.08%. [ABSTRACT FROM AUTHOR]

Silicon (Si) substrates and complementary metal-oxide-semiconductor (CMOS) technology are being used in microdisplays in augmented reality/virtual reality devices owing to higher pixel resolution. Quantum-dot light-emitting diodes (QLEDs) incorporating colloidal quantum dots have emerged as promising devices for display applications owing to their exceptional color, high luminance, and solution processibility. However, studies on QLEDs on Si, particularly for microdisplay applications, remain limited. This study investigated the device characteristics of inverted top-emitting QLEDs using Si substrates and various CMOS process-based electrode materials (aluminum (Al), Al/titanium nitride (TiN), titanium, cobalt, and tungsten) for microdisplay applications. Devices incorporating a thin TiN layer on an Al electrode exhibited the highest efficiency and luminance compared to those with other electrodes. We successfully fabricated red and green inverted top-emitting QLEDs using microdisplay pixel-structured Al/TiN electrodes, with pixel pitch and fill factor of 10.8 μm × 3.6 μm and 72.5 %, respectively. Further, the device efficiency was optimized by changing hole and electron transport layer thicknesses, resulting in different efficiencies and electroluminescence spectra owing to the microcavity effect. Optical simulations demonstrated consistency with the measured values. Thus, the selection of the bottom electrode and a suitable design that considers the microcavity effect are crucial for high-performance QLED-based microdisplays. • Device characteristics of inverted top-emitting QLEDs for microdisplays investigated. • Si substrates and various CMOS process-based electrode materials used for QLEDs. • Red, green inverted top-emitting QLEDs with microdisplay pixel-structured electrodes. • Device efficiency optimized by changing hole and electron transport layer thicknesses. • Optical simulations confirmed consistency with the measured values. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2) and holmium (1.2 mol% Ho3+) doped TiO 2 nanoparticles were synthesized via sol-gel method using polyvinylpyrrolidone (PVP) co-polymer as a pore forming agent. The nanoparticles were dispersed in a solvent and drop-cast on a glass substrate to make films. The films were then calcined at 550 °C for 4 h in a pre-heated muffle furnace. Methylammonium lead iodide (MAPbI 3) was incorporated with TiO 2 and TiO 2 :Ho3+ nanoparticles. Therefore, the samples TiO 2 , TiO 2 :Ho3+, TiO 2 :MAPbI 3 and TiO 2 :Ho3+:MAPbI 3 were obtained and their properties as an electron transporting and photon absorption layers, respectively, were evaluated for possible application in perovskite solar cells. XRD results revealed a rutile phase which was found to be consistent with the RAMAN analysis. FESEM showed spherical nanoparticles with irregular pore size for TiO 2 and TiO 2 :Ho3+ samples, whereas MAPbI 3 nanocrystals seemed to have filled-up the pores in TiO 2 :MAPbI 3 and TiO 2 :Ho3+:MAPbI 3 samples. UV–Vis results showed an expected UV absorption of TiO 2 with the absorption band at ∼366 nm and upon doping with 1.2 mol% of Ho3+ ions, an improved absorption and a shift towards the visible region was observed. Small absorption bands at ∼453, 541 and 645 nm were detected, which are resulting from the Ho3+ transitions. When MAPbI 3 was incorporated with TiO 2 :Ho3+, absorption in the visible range remained improved with the bands at ∼541 and 645 becoming intense. TiO 2 :MAPbI 3 sample showed a further absorption improvement with a red-shift of the absorption band. The band gap energy was estimated and found to be ∼3.00, 2.35, 2.32 and 2.34 eV for TiO 2 , TiO 2 :Ho3+, TiO 2 :MAPbI 3 and TiO 2 :Ho3+:MAPbI 3 , respectively. The red-shift and the reduction of the bandgap values is a good indication that these materials will absorb as much photons in the visible and near-infrared regions. The current-voltage (I–V) analysis revealed that the sample TiO 2 :MAPbI 3 have higher current flow, implying lower resistance in the material. The PL results indicated low electron-hole recombination as the intensity was considerably decreased upon doping with Ho3+ and incorporating MAPbI 3. • Sol-gel synthesis of Ho3+ doped TiO 2 nanoparticles and incorporation with MAPbI 3. • XRD showed that all samples are highly crystalline. • FESEM showed spherical nanoparticles with irregular pore size. • Improved photon absorption and a shift to the visible and near-infrared regions was observed. • Higher current flow, implying lower resistance in the materials was demonstrated. [ABSTRACT FROM AUTHOR]

During the past decade in the perovskite solar cells (PSCs) field, mesoporous titanium oxide (mp-TiO 2) has been widely used as electron transport layers (ETLs) to promote the electron extraction process and also as a scaffold for the perovskite layer (PSK) to gain better PSC performance. Usually, the interface between the mp-TiO 2 layer and PSK needs a modification process to boost the performance of mp-TiO 2 -based PSCs. Here, lithium chloride (LiCl) was used to modify the ETL/PSK interface. Results showed that a simple interface engineering based on LiCl could improve the morphology and crystalline properties of the PSK film, and motivate charge transport processes at the ETL/PSK interface and within PSK due to lower grain boundaries in PSK. Overall, ETL interface engineering with a 0.03 M LiCl solution leads to an efficiency of 11.24% for PSCs, higher than that of 7.42% for control devices. In addition, the modified PSCs compared to control PSCs were more stable in an environment with a humidity of 25%. The improved stability is caused by reduced GBs and a suppressed lead iodide (PbI 2) surplus in the modified PSK. • The photovoltaic properties of PSCs increased by interfacial engineering method. • The recombination processes are suppressed in modified PSCs. • The modified layer drastically passivates grain boundaries in the perovskite layer. • The stability of PSCs increase by employing the interfacial engineering method. [ABSTRACT FROM AUTHOR]

Electron transport layer plays an important role on promoting electron transport and retarding electron recombination in photoelectric device. In this work, magnesium (Mg) doped titanium dioxide (TiO 2) thin film was successfully prepared by the modified sol-gel method. The atomic ratio of Mg atoms to Ti atoms was adjusted to change the light transmittance, band gap and photoelectric performance of TiO 2 thin film. In addition, Mg doped TiO 2 thin film was applied as the compact layer in dye sensitized solar cell (DSSC). The results indicate that the decreased proportion of non-lattice oxygen and the adjusted energy band structure show significant effect on generating more photoelectrons and reducing recombination losses in DSSC. Furthermore, the analysis results of electrochemical impedance spectroscopy (EIS) and open-circuit voltage decay (OCVD) reveal that DSSC based on 15 mol% Mg doped TiO 2 compact layer shows the smallest electron transport impedance and the longest electron lifetime. Therefore, DSSC based on 15 mol% Mg doped TiO 2 compact layer obtains the highest photoelectric conversion efficiency (PCE) of 7.843 %, which is 17.66 % higher than that based on pure TiO 2 compact layer. The prepared smooth and compact Mg doped TiO 2 thin film in this work can also be applied to other thin film optoelectronic devices. • The proportion of non-lattice oxygen of TiO 2 film decreased with Mg doping, which could reduce the electron recombination. • The enhanced transmittance and enlarged bandgap of Mg doped TiO 2 compact layer made the V oc value of device increase. • Mg doped TiO 2 compact layer made DSSC obtain the depressed electron transport impedance and increased electron lifetime. [ABSTRACT FROM AUTHOR]

The third-generation organic solar cells have the benefits of low-cost, solution processability, low energy payback time, environment friendliness and appropriateness for mass production via large area printing techniques. The electron transport layer improves the ohmic contact between the cathode and the photoactive layer. In this research article, we demonstrate a drop on demand inkjet printing of the zinc oxide electron transport layer and the photoactive layer blend consisting of a donor poly(3-hexylthiophene-2,5-diyl) (P3HT) and acceptor Indene C-60 bisadduct (ICBA) of an organic solar cell. Consequently, all inkjet printed solar cell achieved a power conversion efficiency of 4.7% under ambient conditions. We highlighted that drop spacing, substrate temperature and the waveform parameters such as voltage and time are the important parameters for printing. Moreover, we observed a difference in morphology between spin coated and inkjet printed devices as characterized via UV–Visible absorbance, atomic force microscopy and scanning electron microscopy. Furthermore, we applied device characterization from impedance spectroscopy to elucidate the difference in device performance. Particularly, the effective lifetime and global mobilities calculated from the impedance spectroscopy Nyquist plots at 1 Voltage bias in the dark for all inkjet-printed devices are 0.0374 μs and 57.5 × 10−3 cm2/V–S respectively, and for all, spin-coated devices are 0.0628 μs and 115.3 × 10−3 cm2/V–S respectively. Image 1 • Bulk heterojunction organic solar cells in inverted geometry with inkjet printed zinc oxide and P3HT: ICBA. • A higher efficiency of 4.7 % was achieved for all inkjet printed devices which is comparable with the spin coated devices. • The variation in the efficiency of spin coated and inkjet printed devices is due to the morphology changes. • Electrochemical Impedance Spectroscopy proved better charge extraction by electron transport layer and photoactive layer. [ABSTRACT FROM AUTHOR]

The plasmonic property of metal nanoparticles could improve the photovoltaic performance of perovskite solar cells (PSCs). In this work, the plasmonic Au nanoparticles (Au NPs) was introduced into the SnO 2 electron transport layer (ETL), improving the photovoltaic performance of perovskite solar cells (PSCs) based on carbon electrode by approximately 26.28 %. The device structure is the FTO glass/SnO 2 /perovskite (CH 3 NH 3 PbI 3)/carbon electrode. By optimizing the volume of Au NPs, the photocurrent of PSCs increased from 18.49 mA cm−2 to 23.25 mA cm−2 by 25.74 %, and the power conversion efficiency (PCE) from 10.96 % to 13.84 % by 26.28 %. The improved performance of the device is due to the local surface plasmon resonance (LSPR) of Au NPs, which enhances the optical absorption in the perovskite layer and improves the conductivity of the electron transport layer (ETL). Fluorescence spectroscopy showed that PSCs containing Au NPs reduced the recombination of electron and hole between the interface of ETL and perovskite and could transmit charge faster than PSCs without Au NPs. These results indicate that the plasmonic metal nanoparticles can greatly improve the efficiency of PSCs. [Display omitted] • Au NPs with excellent LSPR effects was introduced into the ETL to improve the photovoltaic performance of PSCs. • The improvement in PCE was due to the LSPR of Au NPs enhancing the optical absorption of PSCs and conductivity of the ETL. • The introduction of Au NPs had increased the PCE of the device by 26.28 %. [ABSTRACT FROM AUTHOR]

Numerical simulations can provide the physical insights into the carrier transport mechanism in the solar cells, and the factors influencing their performance. In this paper, perovskite solar cell (PSC) based on the mixed perovskite (CH 3 NH 3 Pb(I 1-x Br x) 3 has been numerically simulated using the SCAPS simulator. A comparative analysis of different electron transport layers (ETLs) based on their conduction band offsets (CBO) has been performed, while Spiro-OMeTAD was used as a hole transport layer (HTL). Among the proposed ETLs, CdZnS performed better and demonstrated the power conversion efficiency (PCE) of 25.20%. Also, the PCE of the PSC has been optimized by adjusting the doping concentrations in the ETL, Spiro-OMeTAD layer, and the thickness of the perovskite light absorber layer. It was found that the doping concentration of 1021 cm−3 for the CdZnS based ETL and 1020 cm−3 for Spiro-OMeTAD are the optimum concentrations values for demonstrating enhanced efficiency. A 600 nm thick perovskite layer has found to be appropriate for the efficient PSC design. For the initial guessing and numerical model validation, the photovoltaic data of a very stable (over one year with PCE ~13%) n-i-p structured (ITO/TiO 2 /CH 3 NH 3 Pb(I 1-x Br x) 3 /Spiro-OMeTAD/Au) PSCs was used. These numerically simulated results signify the optimum performance of the photovoltaic device that can be further implemented to develop the highly efficient PSCs. • PSC based on the mixed perovskite has been numerically simulated using SCAPS simulator. • A comparative analysis of different ETLs based on their CBOs has been performed. • These numerically simulated results signify the optimum performance of the PSCs. [ABSTRACT FROM AUTHOR]