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Sn halide perovskite solar cells (PKSCs) are the most promising competitors to conventional lead PKSCs. Nevertheless, defects at the surfaces and grain boundaries hinder the improvement of the PKSCs' performance. Liquid surface passivation on the perovskite layer is commonly used to decrease these defects. In the case of tin perovskite solar cells, the liquid passivation improved the open-circuit voltage (

Lead-free tin perovskite solar cells (PKSCs) have attracted tremendous interest as a replacement for toxic lead-based PKSCs. Nevertheless, the efficiency is significantly low due to the rough surface morphology and high number of defects, which are caused by the fast crystallization and easy oxidization. In this study, a facile and universal posttreatment strategy of sequential passivation with acetylacetone (ACAC) and ethylenediamine (EDA) is proposed. The results show that ACAC can reduce the trap density and enlarge the grain size (short-circuit current (J

Since the DMSO seriously oxidizes the GeI2 which is one of the ingredients for the Sn/Ge perovskite, it was difficult to make high-quality films by using the conventional DMSO/DMF solvent. We now first report the MASn0.5Ge0.5I3 perovskite solar cells (PSCs) prepared by a simple spin-coating technology. We found that triethanolamine (TEA)/n-methyl pyrrolidone (NMP) does not oxidize the GeI2 and improves the stability of the precursor. The precursor solution with TEA/NMP/DMF gave high-quality perovskite films. The cell gave a power conversion efficiency of 2.18%. This is the first report proving that Sn/Ge PSCs are fabricated by a conventional solution process.

Overcoming Voc loss to increase the efficiency of perovskite solar cells (PSCs) has been aggressively studied. In this work, we introduce and compare rubidium iodide (RbI) and potassium iodide (KI) alkali metal halides (AMHs) as dopants in a tin–lead (SnPb)-based perovskite system to improve the performance of PSCs by enhancing their Voc. Improvement in terms of surface morphology, crystallinity, charge transfer, and carrier transport in the SnPb perovskites was observed with the addition of AMH dopants. Significant power conversion efficiency improvement has been achieved with the incorporation of either dopant, and the highest efficiency was 21.04% in SnPb mixed halide PSCs when the RbI dopant was employed. In conclusion, we can outline the enhancement strategy that yields a remarkable efficiency of >20% with a smaller Voc loss and improved storage, light, and thermal stability in SnPb PSCs via doping engineering.

Transparent-conductive-oxide-free (T-C-O-free) back-contact (B-C) dye-sensitized solar cell (DSC) utilizing flexible Stainless Steel (SS) mesh (SS-mesh) supported with mesoporous TiO2 as a photoanode employing cobalt electrolyte is being presented. A thin layer of Ti metal over the SS-mesh was ascertained to be essential to retard the back electron reaction, which was confirmed by the dark current measurements. The interfacial contact between the SS-mesh and nanoporous (NP) TiO2 of the photoanode of T-C-O-free B-C-DSC was driven to influence the photovoltaic performance greatly. It was confirmed by electrochemical impedance analysis that NP TiO2 of 30 nm exhibited less charge transfer impedance observed at TiO2-dye-electrolyte interface as compared to TiO2 of having particle size of 15–20 nm. T-C-O-free B-C-DSC employing dye mixer combination of indoline dyes D-131 and D-205 (1:1) with relatively larger NP of TiO2 (30 nm) as compared to TiO2 of 15–20 nm exhibited enhanced photoconversion efficiency (PCE) of 4.02%. To increase the PCE even further, T-C-O-free B-C-DSC with cobalt based electrolyte sensitized with porphyrin (YD2-o-C8)-dye bearing a larger optical window was investigated. An optimized 10 µm thickness of the TiO2 layer was found to be optimum leading to an enhanced PCE of 5.26%.

We report that doping with hydrophobic bulky 2D phenylethylammonium (PEA+) is desirable to stabilize the perovskite matrix and enhance its stability. The addition of PEA+ alters the crystal growth orientation and improves the connectivity of the crystal grains. However, solely adding the PEA+ material cannot fully passivate the severe bulk recombination sites/interior defects due to Sn vacancies, leading to an efficiency of 3.96% (Voc of 0.36 V) for a Ge-free device. In contrast, we find that the addition of smaller-sized Ge ions with an optimum doping concentration effectively reduces the leakage current and suppresses the carrier density of the perovskite material. From the perspective of traps, the addition of Ge reduces the traps, typically deep traps, and its effectiveness (Ge) in trap passivation is further deduced from the thermally stimulated current (TSC) profile. The total trap density was doubly reduced to 4.14 × 1020 cm−3 when 7.5 mol% Ge was added, which led to a photo-conversion efficiency of 7.45% with a high Voc of 0.46 V. In addition, defect healing by the Ge additive significantly enhanced the stability of the unencapsulated device for 192 h. This work shows that Ge is an effective additive to suppress the recombination sites (trap state passivation), leading to the establishment of an efficient tin-based perovskite solar cell.

Inorganic CsSnI3 based perovskite crystals are interesting thermoelectric materials, owing to their unusual electronic properties. Here we report the thermoelectric power performance of a solution-coated CsSnI3 thin film from the viewpoint of carrier concentration optimizations. It was found that the carrier concentration can be changed by altering the aging time of the precursor solution. X-ray photoelectron spectroscopy analysis showed that the concentration of metallic Sn4+ increased as the solution aging time increased. This made possible to explore the relationship between carrier concentration and thermoelectric power factor. After controlling Sn4+ concentrations, we report a power factor of 145.10 μW m−1 K−2 , along with electrical conductivity 106 S/cm and Seebeck coefficient of 117 μV/K, measured at room temperature.

Environment-friendly tin perovskite solar cells (T-PKSCs) are the most suitable alternative candidate for lead-free PKSCs. However, the photovoltaic performance of such T-PKSCs is far below those of lead-based perovskite solar cells due to an energetic mismatch between the perovskite layer and charge transport layers. Herein, it is shown that, by partial substitution of the A-site cation using diethylammonium iodide (DEAI) substitution, deeper energy levels are obtained. At the same time, the trap density is reduced and the grain size is significantly improved. The fabricated solar cell shows much enhanced efficiency from 7.31% to 10.28%, short-circuit current density from 18.68 to 21.69 mA cm−2, open-circuit voltage from 0.59 to 0.67 V, and fill factor from 0.67 to 0.71 after DEAI substitution. Such an efficiency improvement can be explained by matching energy levels at the interfaces between perovskite layer and the charge transport layers. In addition, after 50 days of storage, the modified T-PKSCs demonstrate high stability maintaining 78% of its initial efficiency, whereas the reference device degrades to 68% during 28 days storage.

Despite lead halide perovskite(top)/silicon(bottom) tandem solar cell achieving >29% efficiency, the toxicity of lead limits the adoption of perovskites in electronic devices. To solve this problem, tin perovskite has been suggested as an alternative candidate to be used as the top cell. However, most of the reports on tin perovskite solar cells are based on narrow band gap materials (band gap: 1.20–1.40 eV), which are not suitable to be used as the tandem top cell. In addition, the efficiency of the previously reported wide band gap lead-free perovskites is not satisfactory, shown to be less than 2.00%. This study explores the fabrication of the wide band gap (1.61 eV) ASnI2Br perovskite solar cells through the optimization of formamidinium and guanidinium content to improve the efficiency from 1.68 to 7.00%. Substituting the A site with larger cation results in a larger crystal size, which translated into higher device stability. Better energy-level alignment within the device significantly enhanced the charge injection and extraction, which translated into higher open-circuit voltage. This work provides proof that tin-halide perovskite solar cells have the potential in the fabrication of lead-free all-perovskite tandem solar cells. This research was supported by JST Mirai Program (JPMJMI17EA) and the Chinese Scholarship Council (CSC202008050034).

Recently, Sn perovskite solar cell (Sn PVK PV) are attracting attention. However, the efficiency was still lower than that of Pb perovskite solar cells. Recently, the Sn PVK PVs with efficiency higher than 10% have been reported from several research groups. The crystal defects include the presence of Sn4+, Sn2+ defect, I- defect, the presence of Sn0, the interstitial I- and so on. In order to decrease these defect densities, we have proposed some processes such as addition of Ge2+ ion, introduction of ethylammonium cation into A site, and surface passivation of perovskite grain boundary with diaminoethane dilute solution. Our results on efficiency enhancement (13%) is explained by the conduction and valence band energy level against carrier trap depth. In addition, an inverted SnPb perovskite solar cells with 23.3% efficiency is discussed from the view point of optimization of energy alignment.

Tin–lead (Sn–Pb)-based perovskite solar cells (PSCs) still exhibit inferior power conversion efficiency (PCE) compared to their pure Pb counterparts because of high voltage loss (VL) and high photo...

A combination of near infra-red (NIR) photon harvesting and cobalt electrolytes having deeper redox energy level are needed for the fabrication of high efficiency dye-sensitized solar cells (DSSCs). A logical molecular design of unsymmetrical squaraine dye (SQ-110) as a representative of NIR dyes has been demonstrated to function well in DSSC using cobalt complex redox electrolyte. Problem of mass transport limitations due to the bulky cobalt complex ions leading to relatively enhanced charge recombination was amicably solved by single as well as multiple compact metal oxide surface passivation on both of the transparent conducting oxide substrate as well as mesoporous TiO2. Complete absence of light absorption beyond 550 nm wavelength region by D-35 and utilization of a complementary light harvesting dye SQ-110 led to efficient wide wavelength photon harvesting. DSSC fabricated using a dye cocktail of D-35 and SQ-110 in 4:1 ratio resulted in to photoconversion efficiency (PCE) of 7.2%, which is much higher as compared to the constituent individual sensitizers D-35 (3.6%) and SQ-110 (1.9%). This synergistic enhancement in PCE by dye cocktail was associated with the mutual co-operation of respective dyes in terms controlling the dye aggregation and complementary photon harvesting. In this dye cocktail system, D-35 is involved in the prevention of dye aggregation, lower wavelength photon harvesting and energy transfer induced photocurrent enhancement.

High quality perovskite film with high coverage and tight grain arrangement is critical for achieving high-efficiency and high-stability perovskite solar cells (PSCs). In this work, high quality perovskite films were successfully prepared by liquid nitrogen assisted method (LN method). Here, the vaporization of liquid nitrogen reduces the ambient temperature and absorb thermal energy from the substrate surface to accelerate the nucleation of perovskite. The results of scanning electron microscopy (SEM) shows that the perovskite films prepared by liquid nitrogen assisted method were dense and pinhole-free. The devices prepared by the LN method leads to a high-efficiency upto 16.53%, and the high efficiency device could maintain over 89% of the initial power conversion efficiency (PCE) even after 30 days storage in a desiccator at room temperature.

A p–i–n type flexible perovskite solar cell (PSC) employing PEDOT:PSS as a hole transport material was fabricated implementing a synergistic approach to tune the composition and morphology of perovskite films. This was accomplished by the optimization of methylammonium–formamidinium double-cation perovskite, Pb(SCN)2 additive and different anti-solvents to make hysteresis-free flexible PSCs. The PSCs reported exhibit a power conversion efficiency (PCE) of 16.13% with excellent mechanical stability, retaining >90% of the PCE after 1000 bending cycles at a radius (R) of 6 mm. This PCE is amongst the highest reported values for flexible inverted PSCs fabricated on PEDOT:PSS. Although PSCs on rigid conducting glass substrates have been reported to exhibit >20% PCE, long-term stability is of great concern because of poor encapsulation. Solution processability of PSCs gives the freedom to develop them on flexible substrates, which is suitable for commercialization of PSCs. Herein, a novel encapsulation technology of sealing flexible PSCs inside cylindrical glass tubes (R = 8 mm) is being demonstrated. Encapsulated flexible devices retained 90% of the PCE after 6000 hours under ambient conditions.

Lead (Pb) perovskites can be synthetically modified to form colloidal nanocrystals which exhibit remarkable optoelectronic properties in the various fields such as light-emitting devices, flexible electronics, and photodetectors. However, because of the toxicity issue of Pb, nanocrystals of Pb free such as tin (Sn)-based perovskites have got attention. In the present work, we have selected the Sn-based perovskite, Cs2SnI6, owing to the high air and thermal stability. Quantum dots of Cs2SnI6 were prepared by using two methods, namely the hot-injection method and the ultrasonic irradiation method. The difference between Cs2SnI6 particles generated by these two methods was discussed. The particles synthesized by using the hot-injection method were less than 10 nm in size and were aggregated structure due to particle tight-binding energy. On the other hand, the particles by using the ultrasonic irradiation method gave a mono-dispersed solution. The particle size was from several ten nanometers to several hundred nanometers.

Tin (Sn) based perovskite solar cells (PSCs) are rapidly getting attention due to their relatively less toxic nature compared to lead-PSCs. However, Sn perovskites previously reported are narrow-bandgap materials. Wide-bandgap perovskites, which are the key materials for the top layer of lead-free tandem solar cells, are rarely researched up to now. Here, it is demonstrated that optoelectronic properties of the GA0.06(FA0.8Cs0.2)0.94SnI2Br based wide-bandgap perovskite can be improved by exploring (1) Germanium (II) Iodide (GeI2) doping, (2) incorporation of Ethylenediamine Bromide (EDABr2) at A site, (3) EDA passivation. The incorporation of big organic cation EDABr2 in the wide-bandgap tin perovskite crystal structure together with GeI2 doping made the carrier lifetime of perovskite absorber increase from 1.1 ns to 22.8 ns and the power conversion efficiency (PCE) was enhanced from 2.55% to 4.86% with an increment of Voc ˃ 100 mV. Further, we achieved the balanced charge transfer by using EDA passivation on the optimized perovskite surface film. As a result, the efficiency was improved from 4.86% to 7.50%, which is the highest efficiency among lead-free wide bandgap PSCs. This enhanced photovoltaic performance of the wide-bandgap tin perovskite device presents a wide application in lead-free tandem towards commercial development.

Trap states at the interface or in bulk perovskite materials critically influence perovskite solar cells performance and long-term stability. Here, a strategy for efficiently passivating charge traps and mitigating interfacial recombination by SnO2 surface sulfur functionalization is reported, which utilizes xanthate decomposition on the SnO2 surface at low temperature. The results show that functionalized sulfur atoms can coordinate with under-coordinated Pb2+ ions near the interface. After device fabrication under more than 60 % humidity in ambient air, the efficiency of methylammonium lead iodide (MAPbI3 ) perovskite solar cells based on sulfur-functionalized SnO2 increased from 16.56 % to 18.41 % with suppressed hysteresis, which resulted from the accelerated interfacial charge transport kinetics and decreased traps in bulk perovskite by interfacial sulfur functionalization. Additionally, thermally stimulated current studies show the decreased trap density in the shallow trap area after interfacial sulfur functionalization. The interfacial sulfur functionalized solar cells without sealing also exhibited considerable retardation of solar cell degradation with only 10 % degradation after 70 days air storage. This work demonstrates a facile sulfur functionalization strategy by using xanthate decomposition on SnO2 surfaces to obtain highly efficient perovskite solar cells.

A novel and facile strategy to realize selective inorganic ligand (S2−) exchange on Pb-rich surface of PbS colloidal quantum dots (QDs) has been demonstrated. This was achieved via xanthate ligand decomposition at room temperature without damaging the QDs surface. This proposed method offers an amicable solution for the limitation that inorganic-terminated colloidal QDs are restricted by the specific requirement to solvents with high dielectric constant. Furthermore, Introduction of S2− to form sulfur-crosslinking PbS QDs enables reaction force-induced QDs arrays and smooth surface morphology of the spin-coated QDs film as evidenced by atomic force microscopy. Passivation of QDs by bromide combined with sulfur led to stronger electronic coupling between adjacent QDs as compared to bromide-only passivated QDs counterparts. Bromide and sulfur hybrid-capped QDs exhibited remarkably enhanced carrier mobility from 1.66 × 10−4 cm2/V s to 5.0 × 10−1 cm2/V s as evidenced by the Hall- Effect measurement. The smooth QDs film morphology and higher charge transport contributed to the boost in the power conversion efficiency of QDs solar cells up 4.96% compared that using only CTAB passivated PbS QDs solar cells (3.04%). This controlled sulfurization approach paves a potential way for improved optoelectronic properties and devices based on QDs.

TiO2 has been extensively utilized as bottom electron transporting scaffold for perovskite solar cells (PSCs) but need for its high processing temperature (>450 °C) hinders its applicability for the flexible plastic substrates. Use of the low temperature processed ZnO is one of the probable solutions as electron transport layer (ETL) in PSCs owing to its high electron mobility. An amicable solution for the instability of the perovskite absorber layers fabricated on to ZnO leading resulting in to poor power conversion efficiency (PCE) and long-term stability is necessary for to harness the benefit of ZnO as ETL in PSCs. Herein, we modified the ZnO surface by spin-coating an ultrathin Nb2O5 as surface passivation layer. In this work, both of the ZnO and Nb2O5 were fabricated by spin coating and sintered at relatively lower temperature of 200 °C. Utilizing this Nb2O5 surface passivated and low temperature processed ZnO as ETL, dramatically enhanced stability of perovskite film over 20 days under ambient condition has been clearly demonstrated. This bilayer of Nb2O5 surface passivated ZnO scaffold used for fabrication of the planer heterojunction PSCs based on CH3NH3PbI3, led to the maximum PCE of 14.57% under simulated solar irradiation for an optimized ZnO thickness of 42 nm. Moreover, implication of the surface passivation of ZnO by Nb2O5 leading to the formation of highly crystalline, stable and dense perovskite film has been probed by SEM and XRD investigations.

Compared with organic-inorganic perovskites, all-inorganic cesium-based perovskites without volatile organic compounds have gained extensive interests because of the high thermal stability. However, they have a problem on phase transition from cubic phase (active for photo-electric conversion) to orthorhombic phase (inactive for photo-electric conversion) at room temperature, which has hindered further progress. Herein, novel inorganic CsPb1-x Gex I2 Br perovskites were prepared in humid ambient atmosphere without a glovebox. The phase stability of the all-inorganic perovskite was effectively enhanced after germanium addition. In addition, the highest power conversion efficiency of 10.8 % with high open-circuit voltage (VOC ) of 1.27 V in a planar solar cell based on CsPb0.8 Ge0.2 I2 Br perovskite was achieved. Furthermore, the highest VOC up to 1.34 V was obtained by CsPb0.7 Ge0.3 I2 Br perovskite, which is a remarkable record in the field of all-inorganic perovskite solar cells. More importantly, all the photovoltaic parameters of CsPb0.8 Ge0.2 I2 Br perovskite solar cells showed nearly no decay after 7 h measurement in 50-60 % relative humidity without encapsulation.

Development of novel near-infrared (near-IR) dyes compatible with cobalt complex based redox shuttles for their utilization as sensitizer is inevitable for the fabrication of high-efficiency dye-sensitized solar cells (DSSCs). A series of newly designed unsymmetrical squaraine dyes as a model of near-IR sensitizer were synthesized and characterized for their application as far-red sensitizers of DSSCs utilizing Co(bpy)2+/3+ redox electrolyte. It was shown that logical molecular design led to not only energetic tunability of the sensitizers but also the possibility of good far-red photon harvesting up to 750 nm. One of the newly designed sensitizers, SQ-110, bearing two long alkyl substituents in combination with an electron donating methoxy group directly linked to the aromatic ring was par excellent in terms of its photoconversion efficiency among the dyes utilized in this work. DSSC fabricated using SQ-110 as sensitizer and Co(bpy)2+/3+ redox electrolyte furnished a photoconversion efficiency of 1.98% along with good photon harvesting mainly in the far-red wavelength region. It was further demonstrated that dye molecular structure plays a rather more prominent role than their energetics in controlling the overall device performance of the DSSCs.

TiO2 is commonly used as an electron-transporting material in perovskite photovoltaic devices due to its advantages, including suitable band gap, good photoelectrochemical stability, and simple preparation process. However, there are many oxygen vacancies or defects on the surface of TiO2 and thus this affects the stability of TiO2-based perovskite solar cells under UV light. In this work, a thin (monolayer) SbI3 modification layer is introduced on the mesoporous TiO2 surface and the effect at the interface between of TiO2 and perovskite is monitored by using a quartz crystal microbalance system. We demonstrate that the SbI3-modified TiO2 electrodes exhibit superior electronic properties by reducing electronic trap states, enabling faster electron transport. This approach results in higher performances compared with electrodes without the SbI3 passivation layer. CH3NH3PbI3 perovskite solar cells with a maximum power conversion efficiency of 17.33% in air, accompanied by a reduction in hysteresis and enhancement of the device stability, are reported.

A perovskite solar cell (PSC) utilizing a carbon electrode is a potential candidate for industrially viable, low-cost and highly stable photovoltaics. Therefore, it is important to understand the interface between perovskite layer and carbon electrode to achieve the improved performance of PSCs. We demonstrate an improvised two-step perovskite MAPbI3 (methylammonium lead iodide) deposition method, involving a pretreatment of PbI2 on the porous structure of TiO2/ZrO2/Carbon, which led to the difference in performance. A PbI2 passivation layer at the interface between carbon electrode and perovskite resulted in the improved power conversion efficiency (PCE) of 7.30% from 2.21% compared to a one-step perovskite deposition with no pretreatment of PbI2. This study further explores that an enhanced PCE of 6.55% can be achieved with one-step fabrication while keeping the same perovskite. A fascinating methodology, utilizing quartz crystal microbalance (QCM), which involves the adsorption of PbI2 on the carbon su...

Perovskite solar cells have attracted considerable attention owing to their easy and low-cost solution manufacturing process with high power conversion efficiency. However, the fabrication process is usually performed inside a glovebox to avoid moisture, as organometallic halide perovskites are easily dissolved in water. In this study, we propose a one-step fabrication of high-quality MAPbI3 perovskite films in around 50 % relative humidity (RH) humid ambient air by using diethyl ether as an antisolvent and methanol as an additive into this antisolvent. Because of the presence of methanol, the water molecules can be efficiently removed from the gaps of the perovskite precursors and the perovskite film formation can be slightly controlled, leading to pinhole-free and low roughness films. Concurrently, methanol can be used to tune the DMSO ratio in the intermediate perovskite phase to regulate perovskite formation. Planar solar cells fabricated by using this method exhibited the best efficiency of 16.4 % with a reduced current density-voltage hysteresis. This efficiency value is approximately 160 % higher than the devices fabrication by using only diethyl ether treatment. From the impedance measurement, it is also found that the recombination reaction is suppressed when the device is prepared with methanol additive in the antisolvent. This method presents a new path for controlling the growth and morphology of perovskite films in humid climates and laboratories with uncontrolled environments.

High-efficiency perovskite solar cells (PSCs) need to be fabricated in the nitrogen-filled glovebox by the atmosphere-controlled crystallization process. However, the use of the glovebox process is of great concern for mass level production of PSCs. In this work, notable efficient CH3NH3PbI3 solar cells can be obtained in high humidity ambient atmosphere (60-70% relative humidity) by using acetate as the antisolvent, in which dependence of methyl, ethyl, propyl, and butyl acetate on the crystal growth mechanism is discussed. It is explored that acetate screens the sensitive perovskite intermediate phases from water molecules during perovskite film formation and annealing. It is revealed that relatively high vapor pressure and high water solubility of methyl acetate (MA) leads to the formation of highly dense and pinhole free perovskite films guiding to the best power conversion efficiency (PCE) of 16.3% with a reduced hysteresis. The devices prepared using MA showed remarkable shelf life stability of more than 80% for 360 h in ambient air condition, when compared to the devices fabricated using other antisolvents with low vapor pressure and low water solubility. Moreover, the PCE was still kept at 15.6% even though 2 vol % deionized water was added in the MA for preparing the perovskite layer.

Cesium tin halide based perovskite Cs2SnI6 has been subjected to in-depth investigations owing to its potentiality toward the realization of environment benign Pb free and stable solar cells. In spite of the fact that Cs2SnI6 has been successfully utilized as an efficient hole transport material owing to its p-type semiconducting nature, however, the nature of the majority carrier is still under debate. Therefore, intrinsic properties of Cs2SnI6 have been investigated in detail to explore its potentiality as light absorber along with facile electron and hole transport. A high absorption coefficient (5 × 104 cm–1) at 700 nm indicates the penetration depth of 700 nm light to be 0.2 μm, which is comparable to conventional Pb based solar cells. Preparation of pure and CsI impurity free dense thin films with controllable thicknesses of Cs2SnI6 by the solution processable method has been reported to be difficult owing to its poor solubility. An amicable solution to circumvent such problems of Cs2SnI6 has been p...

Back-contacted architectures have been under intensive investigation for that transparent conductive oxide (TCO) less solar cells (SCs) can be easily realized which avoid the transmission loss of light caused by TCO, typically comprised in conventional solar cells. Here, network-like porous Ti was first utilized as the back-contacted electrode, and a new design allows for a novel back-contacted hybrid perovskite SC without TCO and hole selective layer, which shows a power output of 3.88% with long-term stability. In addition, it avoids limit available collection area of electrodes in the recent reported interdigitated electrode (IDE) based back-contacted TCO-less SCs.

CsPbI2Br is one of candidates of the top layer for the all perovskite tandem solar cells. However, the perovskite is prone to change the phase from α (black) to δ (yellow) type. In this research, Cs1-xFAxPbI2Br perovskites were fabricated in an ambient atmosphere, and their properties immediately after the fabrication and the phase stability were investigated. The quality of the perovskite films was enhanced and the trap density was reduced after the incorporation of the FA cations. The phase stability of the Cs1-xFAxPbI2Br perovskite was effectively enhanced. Consequently, the highest power conversion efficiency of 12.28% with open-circuit voltage (Voc) of 1.09 V, current intensity (Jsc) of 15.65 mA cm−2, and fill factor of 72% in the planar solar cell based on Cs0.7FA0.3PbI2Br perovskite is reported. The bandgap was optimized to be about 1.82 eV suitable for all perovskite tandem top layer. Most importantly, all the photovoltaic parameters of Cs0.7FA0.3PbI2Br perovskite solar cells showed ignorable decay after 2 months’ measurement in an ambient atmosphere with the presence of air and humidity without encapsulation.

The bismuth based perovskite with the structure (CH3NH3)3Bi2I9 (MBI) is rapidly emerging as eco-friendly and stable semiconducting material as a substitute for the lead halide perovskites. A relatively higher bandgap of MBI (about 2.1 eV) has been found to be a bottleneck in realizing the high photovoltaic performance similar to that of lead halide based perovskites. We demonstrate the bandgap engineering of novel bismuth based perovskites obtained by in situ sulfur doping of MBI via the thermal decomposition of Bi(xt)3 (xt = ethyl xanthate) precursor. Colors of the obtained films clearly changed from orange to black when annealed from 80 to 120 °C. Formation of sulfur doped MA3Bi2I9 was confirmed by XRD and the presence of sulfur was confirmed through XPS. In this work, obtained sulfur doped bismuth perovskites exhibited a bandgap of 1.45 eV which is even lower than that of most commonly used lead halide perovskites. Hall-Effect measurements showed that the carrier concentration and mobility are much hig...

We report the structural and optoelectronic properties of Zinc oxide (ZnO) nanostructures prepared by hydrothermal method. The morphological, structural and optical properties of the grown ZnO nanostructures were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectroscopy (PL) respectively. Upon addition of relatively small amount of KI during the in-situ hydrothermal growth the nanorods were formed, further increasing the concentration led to increased diameter of these nanorods and finally at relatively higher concentration of KI, ZnO nanosheets were formed. Later these structures were used to fabricate bi-layer ZnO/P3HT based hybrid photodiode. Subsequent hybrid photodiode measurement with ZnO nanorods and ZnO nanosheets indicated that the nanosheets exhibited improved photodiode response. Compared to the ZnO nanorod/P3HT devices, the optimized photodiode with the dense ZnO nanosheets/P3HT have shown significant increase in the rectification ratio and the photosenstivity from 3.21 to 1420 and from 5.85 to 1330 respectively. The enhanced photodiode response of bi-layered devices consisting of ZnO nanosheets indicated that optimizing the shape and size of ZnO nanostructures had a significant influence on the overall photocurrent and the observed results have been explained on the basis of reduction in the defect density with pronounced absorption in the UV region, thus leading to improved transmission of light in the visible range through these layers.

A very good performance under low/diffused light intensities is one of the application areas in which dye-sensitized solar cells (DSSCs) can be utilized effectively compared to their inorganic silicon solar cell counterparts. In this article, we have investigated the 1 SUN and low intensity fluorescent light performance of Titanium (Ti)-coil based cylindrical DSSC (C-DSSC) using ruthenium based N719 dye and organic dyes such as D205 and Y123. Electrochemical impedance spectroscopic results were analyzed for variable solar cell performances. Reflecting mirror with parabolic geometry as concentrator was also utilized to tap diffused light for indoor applications. Fluorescent light at relatively lower illumination intensities (0.2 mW/cm2 to 0.5 mW/cm2) were used for the investigation of TCO-less C-DSSC performance with and without reflector geometry. Furthermore, the DSSC performances were analyzed and compared with the commercially available amorphous silicon based solar cell for indoor applications.

Despite the eminent performance of the organometallic halide perovskite solar cells (PSCs), the poor stability for humidity and ultraviolet irradiation is still major problem for the commercialization of PSCs. Herein, a novel functional organic compound 1‐(ammonium acetyl)pyrene is successfully introduced for preparing the 2D/3D heterostructured MAPbI3 perovskite. Because of the functional organic pyrene group with high humidity resistance and strong absorption in the ultraviolet region, the 2D/3D perovskite film shows notable stability with no degradation in ≈60% relative humidity after even six months and exhibits a high ultraviolet irradiation stability which keeps nearly no degradation after 1 h in the UV Ozone treatment. Planar PSCs are fabricated in the ≈60% relative humidity air outside glovebox. The champion efficiency of (PEY2PbI4)0.02MAPbI3 perovskite solar cells is 14.7% with nearly no hysteresis which is equal performance of 3D MAPbI3 devices (15.0%). This work presents a new direction for enhancing the solar cells' performance and stability by incorporating a functional organic aromatic compound into the perovskite layer.

All-inorganic perovskites have drawn tremendous attentions in view of their superb thermal stability. However, unavoidable defects near the perovskite surface seriously hampers carrier transport and easily results in ion accumulation at the interface of perovskite layer and charge transport layer. Herein, delocalized thiazole and imidazole derivatives iodide salts functionalized on perovskite surface have been investigated comprehensively. These two salts post-treatment on perovskite could efficiently passivate traps arising from Cs+ or I− vacancies. Additionally, these highly п-conjugated delocalized molecules can contribute to the efficient charge transport and prevent ions accumulation at the interface. As a result, sulfur-contained aminothiazolium iodide (ATI) post-treated CsPbI2Br devices showed simultaneous enhanced current density and voltage due to its higher interaction with perovskite lattice, this led to a champion efficiency of 13.91% with superb fill factor of more than 80%, which exhibited dramatic enhancement compared with the control samples (10.12%). Furthermore, surface passivation with delocalized molecules could effectively stabilize CsPbI2Br phase at room temperature or 80 °C annealing in ambient condition (65% RH). Equally important, this surface passivation allowed competitive efficiency of 11.26% with a large-area device (1.00 cm2). This high kill tolerant approach provide a new route to fabricate inorganic perovskite devices with higher efficiency and stability.

TiO

Despite the high efficiency of MAPbI

Compared with organic-inorganic perovskites, all-inorganic cesium-based perovskites without volatile organic compounds have gained extensive interests because of the high thermal stability. However, they have a problem on phase transition from cubic phase (active for photo-electric conversion) to orthorhombic phase (inactive for photo-electric conversion) at room temperature, which has hindered further progress. Herein, novel inorganic CsPb

High-efficiency perovskite solar cells (PSCs) need to be fabricated in the nitrogen-filled glovebox by the atmosphere-controlled crystallization process. However, the use of the glovebox process is of great concern for mass level production of PSCs. In this work, notable efficient CH

Frequently observed high Voc loss in tin–lead mixed perovskite solar cells is considered to be one of the serious bottle-necks in spite of the high attainable Jsc due to wide wavelength photon harvesting. An amicable solution to minimize the Voc loss up to 0.50 V has been demonstrated by introducing an n-type interface with spike structure between the absorber and electron transport layer inspired by highly efficient Cu(In,Ga)Se2 solar cells. Introduction of a conduction band offset of ∼0.15 eV with a thin phenyl-C61-butyric acid methyl ester layer (∼25 nm) on the top of perovskite absorber resulted into improved Voc of 0.75 V leading to best power conversion efficiency of 17.6%. This enhancement is attributed to the facile charge flow at the interface owing to the reduction of interfacial traps and carrier recombination with spike structure as evidenced by time-resolved photoluminescence, nanosecond transient absorption, and electrochemical impedance spectroscopy measurements.