Performanceof Perovskite Based Solar Cells(metal-halide) Swati kandoria , Saket kumar Electronicsand communication engineering department Nationalinstitute of technical teacher training and research Abstract- Perovskite based solar cells have attracted much recent researchinterest due to the large efficiencies reported for simple planar structures.However, there is a lack of clarity in literature on the key functionalparameters that control the eventual efficiencies. In this article, we providea comprehensive modeling framework, well calibrated with experimental resultsfrom literature, to understand/interpret Perovskite based solar cells andsuggest further optimization schemes. Indeed, our results show that the darkand light characteristics of these devices are dominated by recombination inPerovskite layer. Curiously, our analytical model predicts that the opencircuit voltage could be much larger than built-in potential, a resultsupported by both literature results and numerical simulations. Finally, weidentify optimization pathways to achieve >20% efficiency for such solarcells. Index Terms – Perovskitesolar cell, features , material, architecture, model system, trade-off,efficiency, ETL/HTL properties, conclusion, acknowledgement I. INTRODUCTION:A sun based cell, or photovoltaic cell (beforehand named”sun powered battery”), is an electrical gadget that changes over thevitality of light specifically into power by the photovoltaic impact, which isa physical and concoction marvel.
It is a type of photoelectric cell,characterized as a gadget whose electrical qualities, for example, current, voltage,or protection, shift when presented to light. Sun powered cells are the building pieces of photovoltaicmodules, also called sun oriented boards.Sun based cells are portrayed as beingphotovoltaic, independent of whether the source is daylight or a counterfeitlight. They are utilized as a photodetector.
The operation of a photovoltaic (PV) cell requires threefundamental : The retention of light, generating either electron-gap setsor excitons.The partition of charge transporters of inverse kinds. The different extraction of those bearers to an outercircuit. Interestingly, a sun powered warm gatherer supplies warm byretaining daylight, with the end goal of either coordinate warming or aberrantelectrical power age from warm.One of the solar celltype is perovskite solar cell,A perovskitesolar cell is a type of solar cell whichincludes a perovskitestructured compound, most commonly a hybridorganic-inorganic lead or tinhalide-based material, as thelight-harvesting active layer. Perovskite materials such as methylammonium lead halides are cheap to produce and simple to manufacture.Fig.
I (a) shows a schematic of a Perovskite based solar cell. It consists of threematerials sandwiched between two electrodes – front contact (FC) and backcontact (BC). The middle layer is a Perovskite compound that absorbs solarradiation resulting in generation of electron-hole pairs.
The ElectronTransport Layer (ETL) and Hole Transport Layer (HTL) allow selective collectionof charge carriers at their respective electrodes. Although Perovskites form apart of general class of materials having crystal structure as that of calciumtitanium oxide (CaTi03), the compounds reported for solar cell applicationsmostly consist of organo-metallic halides 1-4. Researchers have tried withvarious types of Perovskites by changing the halide group 4-6 and largecarrier diffusion lengths are also reported 7. This allows one to use thickerabsorber material such that almost all solar radiation beyond band gap energycan be absorbed thus resulting in high short circuit current density 1. Thedark and light current of Perovskite cells are dominated by recombination inabsorber region, (b) Voc of the cells depends on the carrier lifetime inPerovskites and could be much greater than the built-in potential, Vbi, (c)carrier mobility in ETL and HTL mostly affect the fill factor, FF, while (d) lTproduct of Perovskite significantly affects both Jsc and FF. Based on oursimulation results, we also prescribe optimization routes to achieve> 20%efficiency for Perovskite based solar cells. II. FEATURES:Metalhalide perovskites possess unique features that make them exciting for solarcell applications.
The raw materials used, and the possible fabrication methods(such as various printing techniques) are both low cost. Their highabsorption coefficient enables ultrathin films of around 500 nm to absorbthe complete visible solar spectrum. These features combined result in thepossibility to create low cost, high efficiency, thin, lightweight and flexiblesolar modules. III. MATERIAL:The name ‘perovskite solarcell’ is derived from the ABX3 crystal structure of the absorber materials, which is referred to as perovskite structure.
The most commonly studiedperovskite absorber is methylammonium lead trihalide (CH3NH3PbX3,where X is a halogen atom such as iodine, bromine or chlorine), with an optical bandgap between 1.5 and 2.3 eV depending on halidecontent. Formamidinum lead trihalide (H2NCHNH2PbX3)has also shown promise, with bandgaps between 1.5 and 2.
2 eV. The minimumbandgap is closer to the optimal for a single-junction cell than methylammonium leadtrihalide, so it should be capable of higher efficiencies.14 The first use of perovskite in a solid state solar cell was in adye-sensitized cell using CsSnI3 as a p-type hole transportlayer and absorber.15 A common concern is the inclusion of lead as a component of theperovskite materials; solar cells based on tin-basedperovskite absorbers such as CH3NH3SnI3 havealso been reported with lower power-conversion efficiencies. IV.
ARCHITECTURES OF PEROVSKSITE SOLAR CELLS ANDSIMULATION METHOD:Three types of perovskite solar cells are designed tosimulate the effects of architectures and material properties on the deviceperformance. A HTM-free perovskite solar cell is given in Fig. 1(a). The solarcell with a perovskite layer sandwiched between ZnO and CuSCN is shown in Fig.1(b). The perovskite solar cell with double light absorbers is firstly designedin Fig. 1(c).
Fig. 1(d) shows the energy level diagram of each layer in thesedevices. SCAPS was developed based on first-principle continuity and Poisson’sequations (see supplemental material for more details). The computer programwas well adapted to simulating transport physics in solid state devices, suchas homojunction, heterojunction, and multijunction, and formulated to analyze,design, and optimize structures intended for microelectronic, photovoltaic, oropto-electronic applications 27. Material parameters set for device simulationare carefully selected from those reported experimental. The UV-visibleabsorption spectrum of MAPbI3 and MAPbBr3 were measured to be used as astarting point for the optimization of the device structure.
V. MODEL SYSTEM:Thedevice characteristics under dark and illuminated conditions are simulatedthrough self-consistent solutions of drift-diffusion and Poisson’s equations8. Various material parameters and band level alignments used in this studyare shown in Fig. 1 (b). Here, ETL (225 nm thick) properties closely match thatof Ti02 9 while the HTL (200 nm thick) properties are adapted fromspiro-MeOTAD lO. We assume uniform photo-generation of carriers inPerovskite- a valid assumption as the reported carrier diffusion lengths (>l/Jm,7)in the Perovskite is much larger than the absorber thickness (300 nm). Thegeneration rate is normalized such that the entire solar spectrwn beyond thePerovskite band gap (assumed as l.55 eV) 2 is absorbed.
We also assume SRH asthe dominant carrier recombination mechanism in Perovskite while ETL and HTLaretreated recombination/generation free. Electrode work functions are asswned tobe 4.2 eV and 5.1 eV for front and back electrode, respectively. VI. PERFORMANCE TRADE-OFFS:Theexcellent match between literature results and our simulations(Fig. 2) indicatethat our modeling methodology is well calibrated and the parameters used areappropriate.
With this as the bench mark, we now identify the criticalfunctional parameters that dictate eventual performance. A. Role of carrierlifetime on Voc Fig.3 (a) indicates that electron and hole concentrations are uniform for most partof absorber under Voc conditions. Equating the photo-generation (rate G) tocarrier recombination (SRH mechanism), we find that the open circuit voltage asgiven by V DC = 2 x 1n(2GrI n) (1) Fig.
3 (b) shows the simulated light I-Vcharacteristics as a function of carrier lifetime , and /J, while /J’ is held aconstant. The inset of part (b) shows that eq. (1) closely predicts thesimulated Voc results, and is independent of /J. REFERENCES1M. Z. Liu, M. B. Johnston, and H.
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