P-type Perovskite Research Articles

Substrate Induced p-n Transition for Inverted Perovskite Solar Cells.

The p- or n-type property of semiconductor materials directly determine the final performance of photoelectronic devices. Generally, perovskite deposited on p-type substrate tends to be p-type, while perovskite deposited on n-type substrate tends to be n-type. Motived by this, a substrate-induced re-growth strategy is reported to induce p- to n-transition of perovskite surface in inverted perovskite solar cells (PSCs). p-type perovskite film is obtained and crystallized on p-type substrate first. Then an n-type ITO/SnO2 substrate with saturated perovskite solution is pressed onto the perovskite film and annealed to induce the secondary re-growth of perovskite surface region. As a result, p- to n-type transition happens and induces an extra junction at perovskite surface region, thus enhancing the built-in potential and promoting carrier extraction in PSCs. Resulting inverted PSCs exhibit high efficiency of over 25% with good operational stability, retaining 90% of initial efficiency after maximum power point (MPP) tracking for 800h at 65°C with ISOS-L-2 protocol.

Ion migration in p-type perovskite MAPbI3 films under an electric field and thin-film transistor device failure.

This study demonstrated a dynamic analysis to investigate the ion migration in p-type perovskite MAPbI3 films under an electric field, revealing its detrimental effects on the electrical performance of MAPbI3-based devices. An additive strategy was proposed to suppress ion migration, thereby facilitating the fabrication of high-performance MAPbI3-based devices.

Optimization of a CH<sub>3</sub>NH<sub>3</sub>SnI<sub>3</sub> based lead-free organic perovskite solar cell using SCAPS-1D simulator

In this study, a CH3NH3SnI3-based perovskite PV cell with the structure (FTO/TiO2/CH3NH3SnI3/Cu2O) was made and optimized by changing the layer thickness, defect density, and doping profile using the solar cell capacitance simulator (SCAPS) 1D simulator. To better understand how the device interface affects carrier dynamics, a synergic optimization of the device is done by altering the electron-transport layer (ETL) and hole-transport layer (HTL) materials. The light glows through the window layer of Sn2O: F, which serves as the transparent conducting oxide layer in our suggested cell construction and then travels over TiO2 as an n-type ETL. Due to its unique features, the p-type perovskite (CH3NH3SnI3) is chosen as the primary absorber layer. Lastly, Cu2O is added as an HTL before the back contact because it has a higher hole conductivity and the proper offsets for spreading the valance and conduction bands. Additionally, Cu2O-based devices outperform frequently utilized spiro-OMeTAD-based devices in terms of efficiency. According to the findings of these simulations, the optimized structure has a power conversion efficiency (PCE) of 41%, an open-circuit voltage of 1.32 V, a short-circuit current density of 34.31 mA/cm2 and a fill factor (FF) of 90.5%. Additionally, the optimized structure has a short-circuit current density of 34.31 mA/cm2.

Remarkable Enhancement of Detectivity and Stability in Flexible n–i–p-Type Perovskite Photodetectors by Concurrent Use of Various Two-Dimensional Materials: Doped Graphene, Graphene Quantum Dots, WS2, and h-BN

Remarkable Enhancement of Detectivity and Stability in Flexible n–i–p-Type Perovskite Photodetectors by Concurrent Use of Various Two-Dimensional Materials: Doped Graphene, Graphene Quantum Dots, WS₂, and h-BN

Combined First-Principles and Machine Learning Study of Thermal Transport and Thermoelectric Properties of p-type Halide Perovskite CsCdX3 (X = Cl, Br)

Combined First-Principles and Machine Learning Study of Thermal Transport and Thermoelectric Properties of p-type Halide Perovskite CsCdX3 (X = Cl, Br)

Interfacial toughening for high-efficiency perovskite solar modules

The distinctive benefits of perovskite solar cells, such as their lightweight nature, high flexibility, and ease of deformation, have garnered significant interest. These characteristics make them well-suited for use in portable electronic devices. Nevertheless, a large efficiency gap still exists between laboratory-based small cells and industrial-oriented large-scale modules. One of the primary reasons for the efficiency losses is the limited adhesion at the brittle interface between the perovskite layer and hole transport layer. Herein, potassium acetate is selected to tailor the interface of perovskite/hole transport layer. The presence of potassium acetate between the perovskite layer and hole transport layer has the potential to enhance the p-type perovskite interface. The strengthening of the interface contact could be verified by the utilization of KPFM and DFT calculations. As a result, the charge separation is accelerated associated with the substantial enhancement in Voc from 1.118 V to 1.139 V and the power conversion efficiency of the solar cell has been enhanced, resulting in an increase from 23.76% to 24.81%. Additionally, the perovskite solar module exhibits little loss, with an efficiency of 21.13% with an aperture area of 29.0 cm2.

Interfacial engineering eliminates energy loss at perovskite/HTL junction.

Realizing efficient FAPbI3-based devices with high open-circuit voltage (VOC) is still challenging, due to severe energy loss between the n-type perovskite and p-type hole-transporting layer (HTL). Here, we developed a strategy involving controlling the formation of iodine vacancies in order to induce formation of p-type perovskite and hence mitigate such energy loss. Post-deposition of n-butylamine iodide was discovered to induce an n-to-p-type transition in the FAPbI3 perovskite and hence form the p-type perovskite/p-type HTL junction. The resultant device realized a VOC of as high as 1.12 V, a value ∼14.3% higher than that of the corresponding n-type FAPbI3 device (0.98 V).

Inhibition of ion diffusion/migration in perovskite p-n homojunction by polyetheramine insert layer to enhance stability of perovskite solar cells with p-n homojunction structure.

Perovskite p-n homojunctions (PHJ) have been confirmed to play a crucial role in facilitating carrier separation/extraction in the perovskite absorption layer and provide an additional built-in potential, which benefits the inhibition of carrier recombination in perovskite solar cells (PSCs) and ultimately improves device performance. However, the diffusion and migration of ions between n-type and p-type perovskite films, particularly under operational and heating conditions, lead to the degradation of PHJ structures and limit the long-term stability of PSCs with PHJ structure (denoted as PHJ-PSCs). In this study, we propose an insert layer strategy by directly introducing an ultra-thin polyetheramine (PEA) layer between the n-type and p-type perovskite films to address those challenges arising from ion movements. Femtosecond transient absorption (fs-TAS) and photoluminescence (PL) measurements demonstrate that the PHJ (without and with the insert layer) enhances carrier separation/extraction compared to the single n-type perovskite film. Monitoring the evolution of bromine element distribution reveals that the insert layer can efficiently suppress ion diffusion between perovskite films, even under long-term illumination and heating conditions. Consequently, an efficiency of 23.53% with excellent long-term operational stability is achieved in the optimized PHJ-PSC with the insert layer.

Hole Transport Materials for Tin-Based Perovskite Solar Cells: Properties, Progress, Prospects.

The power conversion efficiency of modern perovskite solar cells has surpassed that of commercial photovoltaic technology, showing great potential for commercial applications. However, the current high-performance perovskite solar cells all contain toxic lead elements, blocking their progress toward industrialization. Lead-free tin-based perovskite solar cells have attracted tremendous research interest, and more than 14% power conversion efficiency has been achieved. In tin-based perovskite, Sn2+ is easily oxidized to Sn4+ in air. During this process, two additional electrons are introduced to form a heavy p-type doping perovskite layer, necessitating the production of hole transport materials different from that of lead-based perovskite devices or organic solar cells. In this review, for the first time, we summarize the hole transport materials used in the development of tin-based perovskite solar cells, describe the impact of different hole transport materials on the performance of tin-based perovskite solar cell devices, and summarize the recent progress of hole transport materials. Lastly, the development direction of lead-free tin-based perovskite devices in terms of hole transport materials is discussed based on their current development status. This comprehensive review contributes to the development of efficient, stable, and environmentally friendly tin-based perovskite devices and provides guidance for the hole transport layer material design.

De Novo Studies of Working Mechanisms for Self-Driven Narrowband Perovskite Photodetectors.

Self-driven narrowband perovskite photodetectors have recently attracted significant attention due to their simple preparation, high performance, and amenability for system integration. However, the origin of narrowband photoresponse and the related regulation mechanisms still remains elusive. To address these issues, we herein perform a systematic investigation by formulating an analytic model in conjunction with finite element simulation. The optical and electrical simulations have resulted in design principles for perovskite narrowband photodetectors in terms of the dependence of external quantum efficiency (EQE) on perovskite layer thickness, doping concentration, and band gap as well as trap state concentration. Careful investigations on the profiles of electric field, current, and optical absorption reveal the dependence of narrowband EQE on the direction of incident light and perovskite doping types: only p-type perovskite can yield the narrowband photoresponse for illumination from the hole transport layer (HTL) side. The simulation results demonstrated in this study shed new light on the mechanism of perovskite-based narrowband photodetectors and provide valuable guidance for their design.

Photo-enhanced seebeck coefficient by photoinduced carrier dedoping in air-stable MAPbI3

We present an enhanced photo-Seebeck effect in air-stable MAPbI3 by optical gating, where both the Seebeck coefficient (SC) and the electrical conductivity increase significantly when illuminated by a laser diode.A PbI2-rich MAPbI3perovskite pellet exhibitedn-type charge carrier transport and showed a significant increase in the magnitude of the SC in air upon illumination. Compared with the p-type perovskite, the n-type MAPbI3 perovskite showed higher Seebeck enhancement, along with higher photoconductivity.This indicates that the residual PbI2in then-type perovskite accelerates photoinduced charge transfer at the MAPbI3/PbI2interface. The enhanced photo-Seebeck effect through dedoping induced by charge transfer can be applied to increase the thermoelectric figure of merit (ZT) in thermoelectric materials using non-destructive methods.

A heterostructure p-n junction constituting of fluorite and perovskite semiconductors for electrochemical energy conversion

A semiconductor heterostructure material based on p-type cubic perovskite Ba0.9K0.1Fe0.5Co0.5O3-δ (BKFC) and n-type fluorite Sm0.075Nd0.075Ce0.85O2-δ (SNDC) forms micro p-n junctions in the low-temperature solid oxide fuel cells (LT-SOFCs) improving the electrochemical performance. A highly power density of 911 mW·cm−2 at 550° C was obtained with this material combination as electrolyte in a fuel cell, which is 20 % higher than that of the LT-SOFCs with pure BKFC as electrolyte. An ionic conductivity of 0.14 S·cm−1 at 550° C was achieved when equal amounts of BKFC and SNDC were employed as the electrolyte. Profound analysis of the heterostructure p-n junction shows that it blocks electron transport through mixed electronic and ionic conductor and enhances ionic transport improving the electrochemical performance of the fuel cell. The BKFC-SNDC composite electrolyte materials is a potential electrolyte material for raising the power density of fuel cells at lower temperatures.

High-Efficiency p-n Homojunction Perovskite and CIGS Tandem Solar Cell

Efficiency has been known to be one of the most important factors in a solar cell. This article presents the results of a simulation performed on a perovskite/CIGS dual-junction solar cell. In this report, first, a top solar cell consisting of a perovskite absorber layer is simulated using the pn-junction; the separation and transfer of carriers in this structure are done by the internal electric field. The pn-junction has a discharge area smaller than the pin-junction, which increases carrier recombination and reduces optical losses. The perovskite band gap of 1.9 eV is considered, and the efficiency is 21.65% using the Au electrode. Then, the bottom solar cell is fabricated with a CIGS absorbent layer with a 1.4 eV band gap and an efficiency of 11.46%. After simulating and evaluating the performance of the top and bottom solar cells independently, both cells were simulated and examined for the dual-junction state. Since the perovskite and CIGS band gaps are both adjustable, these two materials can act as a proper partner for an absorbent layer in a dual-junction solar cell. In this structure, instead of the usual connection of p-i-n and n-i-p perovskite, n-type and p-type homojunction perovskite connection is used, in which the transfer and separation of carriers are done by an internal electric field. Due to the fact that in this structure, the discharge area is smaller, the recombination of carriers is increased, and the light losses are reduced, which will increase the absorption and efficiency of the cell. The results show that in the tandem design, we encounter an increase in Voc (2.25 V), thus increasing the efficiency of the solar cell (30.71%).

Identifying the potentials for charge transport layers free n-p homojunction-based perovskite solar cells

Perovskite solar cells (PSCs) with no charge transport layers (CTLs) could be one of the major device architectures for the production of simple and low-cost devices. However, CTLs-free PSCs based on n-p homojunction have yet to show high power conversion efficiency (PCE), which is most likely due to inadequate light-and charge-management in the p-type perovskite. The device operation is examined using Solar Cell Capacitance Simulator (SCAPS)-software, and a novel n-p homojunction design is proposed to attempt efficient CTLs-free PSCs. Several aspects of p-type layer that can affect device performance, such as acceptor density, photon-harvesting capability, defects density, and resistances to the transport of charge-carriers are scrutinized and adjusted. Furthermore, the effects of different work-functions of metal electrodes are examined. A suitable acceptor concentration is required for oriented charge transport. It is determined that a p-type perovskite with a thickness of 0.3 μm is advantageous for high performance. A metal electrode with a high work-function is essential for efficient device. Consequently, a PCE of 15.60% is obtained with an optimal defect density of E15 cm−3, indicating that n-p homojunction-based CTLs-free PSCs are promising since they simplify the device design and fabrication process while retaining an acceptable PCE.

High Performance P-Type Perovskite Lagao3 Thin Film Field Effect Transistor Prepared by Solution-Processed

Metal oxide semiconductor (MOS) is essential to compose high-performance electronic devices, however, the investigation on p-type MOS is relatively rare compared with its n-type counterpart. In this work, LaGaO3 thin films with superior p-type conductivity have been prepared via a facile solution process. Moreover, we have implemented Al2O3 and SiO2 as the dielectric of the p-channel LaGaO3 thin film transistors (TFTs) annealed at different temperatures. Particularly, the LaGaO3/Al2O3 TFTs annealed at 700 °C exhibit an ultrahigh hole mobility of 12.4 cm2V-1s-1, Under the same conditions, LaGaO3/Al2O3 thin film transistor is two orders of magnitude higher than LaGaO3/SiO2 thin film transistor. The advanced p-type characteristics of the LaGaO3 thin film, along with its facile low-cost fabrication process can shed new light on future design of high-performance complementary MOS circuit with other optimized facile-integrated dielectrics.

Numerical simulation of novel designed perovskite/silicon heterojunction solar cell

In this work, novel designed solar cell is proposed for first time for doped perovskite based silicon heterojunction solar cells where (n/p)-type doped perovskite used as ultra-thin emitter layer and (p/n)-type silicon as absorber layer. Performance of two different types of solar cells, n-type doped perovskite with p-type based crystalline silicon (p-cSi) solar cells and p-type doped perovskite with n-type based crystalline silicon (n-cSi) solar cells are studied and highest efficiency of 28.82% and 29.48% respectively are achieved by optimizing their properties. Thicknesses of silicon wafer and perovskite layer, band gap of MAPbI3 layer, doping density of ultra-thin perovskite (emitter) layer, doping density of c-Si layer, texturing of silicon wafer, metal work function of different materials at front contact and back contact & its band bending on using different metals, and role of ZnO and ITO as conducting surface layer has been studied and optimized in the present work. AFORS-HET automat simulation software is used to study the performance of these simulated solar cells.

Performance optimization of homojunction perovskite solar cells by numerical simulation

Perovskite materials possess n-type and p-type electrical conductivity through a control over perovskite precursor composition and stoichiometry during the film formation. A p-n homojunction can be constituted between the p-type perovskite and the n-type perovskite and a built-in electric field is formed, which can promote the oriented transportation of the photon-generated carriers and reduce the carrier recombination losses. In this paper, the numerical simulation of p-n homojunction methylammonium lead iodide (MAPbI 3 ) solar cells has been performed and the effects of different electron transport layer (ETL) materials and hole transport layer (HTL) materials, defect density and thickness of the absorber layer and interface defect density on the device photovoltaic performance have been studied. Simulation results show that TiO 2 and Spiro-OMeTAD are the most promising ETL material and HTL material, respectively. To improve device performance, the defect density of the p-type MAPbI 3 absorber layer needs to be as low as 10 15 cm −3 and an optimal absorber thickness of 0.4 μm needs to be guaranteed. Moreover, the device performance is further improved by maintaining the interface defect density less than or equal to 10 9 cm −2 . With these optimizations, a conversion efficiency of 27.10% is achieved for the homojunction perovskite solar cells with a structure consisting of FTO/TiO 2 /n-type MAPbI 3 /p-type MAPbI 3 /Spiro-OMeTAD/Au. Hence, the device structure with perovskite homojunction provide an effective approach towards development of highly efficient solar cells. • Homojunction MAPbI 3 solar cells have been simulated with efficiency of 27.10%. • The effect of different electron transport layer and hole transport layer materials has been investigated. • The impact of bulk defect density and interface defect density has also been studied.

Hot-Probe Method for Majority Charge Carrier Determination in Methylammonium Lead Halide Perovskites

Perovskites, due to their promising capabilities, are among the major candidates to substitute early-generation silicon solar cells. Despite their outstanding electrical and optical properties, actual comprehension of their behavior requires further studies and also investigation tools. It is shown that vacancy traps in organic-inorganic perovskites induce different polarities, where lead and methylamine vacancies posses p- and n-type polarity, respectively. Referred to as the self-doping property, different molar ratios of chemical precursors lead to controllable polarity and intrinsic doping. In other reports, thermal annihilation is also shown to convert p-type perovskite to n-type. According to the broad range of synthesized perovskites and their current application and promising future in optoelectronic devices, a simple, quick, and dependable method for trap concentration and major carrier-type determination is essential. Hot probe is a simple, affordable, and fast method for extracting polarity type in bulk and thin-film semiconductors. So far, this method and its variations have been applied for measuring conductivity, polarity, and impurity concentration in diverse ranges of semiconductors. In this method, free carriers are generated by raising the temperature of hot-probe contact and induced diffusion from this contact toward the other cold contact is studied. An equilibrium state is reached as a result of the formed built-in electric field between the cold and hot electrodes and also temperature elevation of this cold electrode, which act as diffusion dampers. Here, different types of organic-inorganic perovskites are synthesized and their electrical behavior is evaluated by the hot-probe method. Finally, it is concluded that the hot-probe approach is a dependable, fast, and accurate method to be applied in the field of perovskite material evaluations.

Electrodeposition in Ionic Liquids for Controlled Synthesis of New Class of Ionic Semiconductors Based on Binary and Ternary Chalcogenide Perovskites for Thin Film Photovoltaic Solar Cells

Thin film photovoltaic (PV) solar cells based on Cu(In,Ga)(S,Se)2 (CIGS), CdTe and Cu2ZnSnS4 (CZTS) have been in the forefront of the pursuit for sustainable and pervasive solar electricity utilization. Recently, researchers have focused on alternative semiconductor photo-absorbers that can be synthesized as thin films by simple low cost solution based methods. Efforts in this direction led to solar cells based on the hybrid organic-inorganic perovskite photo-absorbers having the general formula RNH3MX3 where R= CnH2n+1, M= Pb, Sn and X= Cl, I or Br showing significantly high (24.2%) conversion efficiency. However, the light induced instability, mechanical durability and thermal degradation problems though largely elucidated, still require intensive efforts towards alleviation. The key factors for high efficiency of hybrid perovskite cell are high absorption coefficient, defect-tolerance and large carrier diffusion lengths. This is attributed to their ionic character derived from higher cation-anion coordination resulting in enhanced Coulomb interaction. The entirely inorganic chalcogenide perovskites are the ionic semiconductor counterparts which are purported to have similar optoelectronic properties sans the stability issues but have not been investigated in detail. The perovskite ionic semiconductors with formula unit ABX3 (A=Ca, Ba or Sr ; B=Ti or Zr; X= S, Se) have direct 0.8-2.4 eV bandgap, high photo-absorption and large carrier mobility. These appear attractive for photovoltaic solar cell application but are needed to be investigated as thin films by emphasizing the synthesis-property correlations. In this work we have investigated electrodeposition synthesis in ionic liquid medium of the transition metal layered chalcogenide TiS2 and p-type CaTiS3 perovskite chalcogenide semiconductor thin films which have application in solar cells, the former as a hole conductor and the later as an efficient photo-absorber.In this work we describe an ab initio study of scalable electrodeposition of TiS2 and CaTiS3 polycrystalline semiconductor thin films from choline chloride–urea eutectic based ionic liquid electrolytes at 80°C and establish their structure and optoelectronic properties dependent upon the electrodeposition variables. The ionic liquid electrodeposition, not studied in detailed for semiconductor layers, is unique due to large stable potential window, high solubility for metal salts and devoid of hydrogen interference usual in aqueous medium. Further, it enables electrodeposition of semiconductor with elements having high reduction potential like Ca and Ti. We synthesized these films by electrodeposition in a 3-cell assembly with Pt reference and counter electrode and transparent conducting glass (FTO) as substrate. Precursors TiCl4, CaCl2 and Na2S2O3 served as source of Ti, Ca and S and initial cyclic voltammetry (CV) studies with variable precursor composition have established deposition potentials of Ca and Ti as -0.68V and -0.79V vs Pt, respectively.Detailed CV study with variable Ca:Ti precursor ratio coupled with film composition analysis establishes deposition potential and precursor composition for stoichiometric CaTiS3 film synthesis. X-ray diffraction showed as-electrodeposited films are polycrystalline. The Raman spectra includes numerous peaks in the 50-1200 cm-1 range which are interpreted as characteristic vibration modes of CaS at 170 and 220 cm-1. The variation in the intensity of the A1g mode at 359 cm-1 originating from TiS2 was used to calibrate the deposition potential relative to film composition. Tauc analysis of the uv-vis transmission spectra showed direct bandgap of 1.5 eV which is ideal for terrestrial solar radiation absorption. A correlation of the electrochemical deposition potential with the inclusion of secondary phases was noticed. This also resulted in the increase in the bandgap energy indicating possibility for adjusting bandgap for specific solar cell structures. The TiS2 layered chalcogenide with potential use as hole transport layer in chalcogenide perovskites was likewise electrodeposited. Detailed analysis of the reduction peaks in CV plots shows peak at -0.76V vs Pt corresponding to TiS2 formation and a rapidly rising current wave corresponds to under potential deposition. The direct electrodeposition of TiS2 is by reduction of Ti at substrate and instant sulfurization in presence of S2- ions. The granular growth is directed by FTO which provides electrochemical reduction and nucleation sites for TiS2 polycrystalline film growth as established by X-ray diffraction. All Raman peaks are interpreted belonging to TiS2 and partial phase mixing with the TiS3 depending on the electrodeposition potential was seen. Thus, the observed decrease in the bandgap with increase in potential can be used for integrating TiS2 in solar cells as hole conductor as well as an absorber depending on the configuration, This paper will report on the detailed effect of the variables used in ionic liquid electrodeposition and consequent structural and optoelectronic properties of the two important ionic semiconductors for assessment of their use in solar cells.

Selection of contact materials to p-type halide perovskite by electronegativity matching

The performance of perovskite optoelectronic devices depends critically on the contact between the active layer and charge transport materials. To reveal the mechanism of barrier formation on perovskite surfaces, we studied Schottky junctions between various metals and a p-type perovskite CsSnBr3. By constructing slab models of the junction interface and aligning atomic core levels, the contacts between Au/CsSnBr3 and graphite/CsSnBr3 were found to be ohmic, but various other metals produced Schottky junctions with CsSnBr3. These calculation results, supported by x-ray photoelectron spectroscopy measurements, suggest that the barrier height of a metal/CsSnBr3 junction is a linear function of the metal’s electronegativity, rather than its work function. By introducing the concept of effective electronegativity for compounds, this trend was extended to a general rule that a suitable transport material should have an effective electronegativity to match that of the perovskite.