Selective Contacts Research Articles

Switchable All Inorganic Halide Perovskite Nanocrystalline Photoelectrodes for Solar‐Driven Organic Transformations

All inorganic halide perovskite nanocrystals (NCs) are considered as fascinating materials for a wide range of optoelectronic applications encompassing photovoltaics, lasing, sensing, and photocatalysis due to their outstanding optoelectronic properties. Herein, it is demonstrated that the photoelectrochemical behavior of CsPbBr3 NC films can be tailored through engineering the selective contacts and accepting species in the electrolyte. This concept has been successfully applied to the photoelectrochemical oxidation of benzyl alcohol (BzOH) to benzyl aldehyde (BzCHO) and the reverse photoelectrochemical reduction of BzCHO to BzOH, demonstrating that CsPbBr3 NCs activate both reactions with photocurrents up to 40 μA cm−2 toward BzCHO production and 5 μA cm−2 for the reverse reaction at 0.15 V versus normal hydrogen electrode. The obtained results highlight the huge potential and versatility of halide perovskite NCs for photoelectrocatalytic applications, validating the implementation of these materials for a wide range of solar‐driven complex organic transformations, and emphasizing the urgent need for stabilization strategies to move beyond the proof‐of‐concept stage to relevant technological developments.

Study of Electron Transport Layer‐Free and Hole Transport Layer‐Free Inverted Perovskite Solar Cells

The selective contacts in perovskite solar cells play a major role in solar cell (SC) performance and optimization. Herein, the inverted architecture is focused on, where systematically the electron transport layer (ETL) and the hole transport layer (HTL) from the SC structure are eliminated. Three main architectures of the SCs are studied: a fully inverted structure, an ETL‐free structure, and a HTL‐free structure. Cathodoluminescence and photoluminescence are measured on various architectures, revealing the electron and hole injection efficiency from the perovskite to selective contacts. Moreover, surface voltage spectroscopy shows the type and the band‐edge transition of these layers. Finally, the photovoltaic (PV) performance of different SCs shows that eliminating the HTL is most critical for PV performance, compared with ETL‐free and fully inverted SC configurations. Current−voltage hysteresis curves prove that efficient selective contacts are essential to eliminate this phenomenon. Measuring the ideality factor shows that the dominant mechanism in ETL‐free SCs is surface recombination, whereas in the other cases, it is Shockley–Reed–Hall recombination. This work provides knowledge about the functionality of methylammonium lead iodide as an electron conductor and as a hole conductor.

Admittance Spectroscopy of Solar Cells Based on Selective Contact MoOx/Si Junction

Admittance Spectroscopy of Solar Cells Based on Selective Contact MoOx/Si Junction

ZnO thickness and ZnTe back contact effect of CdTe thin film solar cell Voc and efficiency progression

CdTe thin film (TF) solar cells are most promising photovoltaic (PV) technology in commercial platform. Back contacts and interface defects related opto-electrical losses are still vital to limit its further technological benefit. TF PV cells shallow recombination and parasitic loss lessening purpose carrier selective back contact with band matching window layers are essential. Beside that back and front contact thickness choice is vital for field associated selective carrier collection and generous optical transmission into the active junction of the cell. It can make variation of cell efficiency. Window and front contact layers band edge variation and back contact thickness effect is analyzed by SCAPS-1D simulation software. ZnO and SnO2 front contact for CdS and CdSe window layers effect are numerically studied for 1 μm CdTe thin film PV cell. Significance of materials for front contact and its thickness effect on current density while ZnTe back surface field contact thickness effect on open circuit voltage and efficiency are demonstrated. Finally, ZnO/CdS/CdTe/ZnTe cell of 0.925 V open circuit voltage and 19.06% efficiency has been achieved for 90 nm of ZnTe with Molybdenum (Mo) back contact.

Electronic-beam evaporation processed titanium oxide as an electron selective contact for silicon solar cells

This work is dedicated to the study of electronic-beam (e-beam) evaporated titanium oxide (TiOx) contact for polycrystalline silicon hetero-junction solar cells. A TiOx material obtained by e-beam evaporation method is suggested as a possible alternative to the atomic layer deposition (ALD) process. The purpose is to achieve corresponding passivation efficiency between e-beam evaporation of TiOx and the ALD method. However, the TiOx in question achieved a relatively low passivation performance of Seff = 113 cm−1 in comparison to the reported ALD results. Nonetheless, as e-beam evaporation is well-established and an environmentally friendly deposition technology, e-beam evaporated TiOx passivation layer has potential for improvement. What is clearly demonstrated in our work is how such an improvement in contact resistance dropped from >55 Ω/cm2 to 2.29 Ω/cm2. Indeed, our study established a correlation between the main process parameters of e-beam evaporation and their influence on the quality of electron selective TiOx layer. Moreover, we reveal a possible scenario for the implementation of e-beam evaporated Titanium oxide as electron selective contact for asymmetrical hetero-junction solar cells.

Fabrication of a Hydrogenated Amorphous Silicon Detector in 3-D Geometry and Preliminary Test on Planar Prototypes

Hydrogenated amorphous silicon (a-Si:H) can be produced by plasma-enhanced chemical vapor deposition (PECVD) of SiH4 (silane) mixed with hydrogen. The resulting material shows outstanding radiation hardness properties and can be deposited on a wide variety of substrates. Devices employing a-Si:H technologies have been used to detect many different kinds of radiation, namely, minimum ionizing particles (MIPs), X-rays, neutrons, and ions, as well as low-energy protons and alphas. However, the detection of MIPs using planar a-Si:H diodes has proven difficult due to their unsatisfactory S/N ratio arising from a combination of high leakage current, high capacitance, and limited charge collection efficiency (50% at best for a 30 µm planar diode). To overcome these limitations, the 3D-SiAm collaboration proposes employing a 3D detector geometry. The use of vertical electrodes allows for a small collection distance to be maintained while preserving a large detector thickness for charge generation. The depletion voltage in this configuration can be kept below 400 V with a consequent reduction in the leakage current. In this paper, following a detailed description of the fabrication process, the results of the tests performed on the planar p-i-n structures made with ion implantation of the dopants and with carrier selective contacts are illustrated.

A novel passivating electron contact for high-performance silicon solar cells by ALD Al-doped TiO2

Titanium oxide (TiO2) thin film has attracted wide interest in high-efficiency silicon solar cells as an electron selective contact due to its low conduction band offset with silicon and an excellent level of passivation, while the incorporation of a small amount of dopants is also expected to improve the performance of thin films. In this work, assisted with density functional theory (DFT) modelling, we study the electronic band structure of aluminum (Al)-doped TiO2 (ATO). The atomic-layer-deposited (ALD) ATO thin films are successfully prepared, and the elemental analysis, passivation effect, thermal stability, conductivity and optical properties of the ATO are systematically investigated. An ultra-high effective minority carrier lifetime (τeff) of 1.9 ms and a low contact resistivity (ρc) of 0.1 Ω·cm2 are simultaneously achieved on silicon wafers. Meanwhile, it is found that the ATO thin films possess better thermal stability than the TiO2 thin film. Finally, a large-area (118.7 × 100 mm2) p-type passivated emitter and rear contact (PERC) solar cells integrated with an ALD ATO layer on the illumination side was fabricated, and a champion efficiency of 21.4% was achieved with an optimal Al concentration in ATO, which is significantly higher than a PERC solar cell with intrinsic TiO2. This work shows ATO a very attractive alternative achieving high-efficiency crystalline silicon solar cells.

Selective Energy Contacts and Multi-Wavelength Solution-Processed Quantum Dot Infrared Photodetector

In this work, a three-channel infrared photodetector with three independent related electric signals as a single optoelectronic chip has been introduced. The proposed structure has been implemented by exploiting an array of PbSe/ZnSe quantum dots and the PbSe/ZnS selective energy contacts considering solution-processed nanotechnology. The electron transport system has been designed to allow the transmission of electrons stimulated by three wavelengths simultaneously from different paths to the corresponding output. The high efficiency, simplicity and fabrication ease, cost-effectiveness, and high tunability of the photodetector have been accomplished as a consequence of solution-process technology. Moreover, the dark current has been significantly declined as a consequence of resonance tunneling in the proposed selective energy contacts. Last but not least, our proposed multi-wavelength ( λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> =2.9 μm, λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> =2.25 μm, λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> =1.75 μm) infrared photodetector has been promising candidates for a wideband spectrum analyzer or multi-wavelength infrared camera.

On the limiting efficiency for silicon heterojunction solar cells

Silicon heterojunction (SHJ) solar cell, as one of the promising technologies for next-generation passivating contact solar cells, employs an undiffused and n-type mono-crystalline silicon (c-Si) substrate and two amorphous-silicon-based selective contacts with opposite polarities. In this work, a numerical model based on Richter's theory has been developed to simulate the performances of a 25.11 % efficiency SHJ solar cell obtained recently. Analyses on series resistivity (Rs) explicit that the upper bound for the sum of contact resistivities for p-type (ρc,p) and n-type (ρc,n) contacts is 0.073 Ω cm2. With the updated contact resistivities, the theoretical limiting efficiency estimated by Brendel's formulation is therefore 28.5 % for SHJ solar cells, which is comparable to 28.7 % for bi-facial tunneling-oxide passivating contact (TOPCon) solar cells. A hybrid structure consisting of p-type contact from SHJ and n-type contact from TOPCon is feasible to reach 28.9 % limiting efficiency in principle, showing potential of solar cells with hybrid structures.

Efficiency Improvement of Perovskite Solar Cells by Utilizing CuInS₂ Thin Layer: Modeling and Numerical Study

Perovskite-based devices are a promising candidate for the next generation of photovoltaic devices. Depending on the selective contacts layers and their interfaces with the absorber, the performance and photoelectric parameters of the perovskite solar cells (PSCs) can be changed. So, it is possible, to achieve highly efficient and stable PSCs by engineering the selective contacts layers and their interface with the perovskite layer. In this study, inorganic CuInS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (CIS) was inserted between the perovskite and Spiro–OMeTAD for decreasing charge recombination at the interfaces. The impact of the CIS and Spiro–OMeTAD on the solar cell photoelectrical parameters is theoretically modeled, and the performance of the solar cells was examined with Solar Cell Capacitance Simulator (SCAPS-1D) under AM1.5G spectrum at 300 K. Results show utilizing a thin layer of CIS can improve the performance of the solar cell. Photovoltaic characterization of the solar cell with CIS shows 18.13%, 73.34%, 1.09 V, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$22.69\,\,{\mathrm {mA}}\,\cdot \, {\mathrm {cm}}^{-2}$ </tex-math></inline-formula> , respectively, for efficiency, fill factor (FF), <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{{\mathrm {oc}}}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{{\mathrm {sc}}}$ </tex-math></inline-formula> . These results indicated a 7% improvement in efficiency increased and 2% on FF increased compared with the structure without CIS. High-mobility CIS can extract more carriers. It is believed this study can provide guidelines for the design and production of economic and stable PSCs with further efficiency enhancement.

Improving Performance of Bifacial‐Grid III–V Solar Cells Bonded on Glass by Selective Contact Annealing

Selective contact annealing is developed to improve the performance of bifacial‐grid III–V top cells bonded on glass by epoxy resin for Si‐based tandem solar cells. The annealing method can minimize the damage to the bonding layer and is compatible with the industrial evaporation technique for contact fabrication. The improvement of the front contact quality by selective annealing treatments is demonstrated through optical and electrical characterization which shows a significantly enhanced III–V device performance. Furthermore, a fitting model is established to reveal the mechanism underlying the performance improvement through the reduction of contact resistances and the bad contact area. Herein, an effective annealing approach to fabricate high‐quality metal–semiconductor contacts for devices with poor thermal resistivity is demonstrated, which can be used in polymer‐bonded top cells in Si‐based tandem solar cells and other flexible optoelectronic devices on polymer substrates.

Indium tin oxide obtained by high pressure sputtering for emerging selective contacts in photovoltaic cells

This article studies the physical and electrical behavior of indium tin oxide layers (ITO) grown by an unconventional technique: High Pressure Sputtering (HPS), from a ceramic ITO target in a pure Ar atmosphere. This technique has the potential to reduce plasma induced damage to the samples. The aim is to obtain, at low temperature via HPS, good quality transparent conductive oxide layers for experimental photovoltaic cells with emerging selective contacts such as transition metal oxides, alkaline metal fluorides, etc. We found that the resistivity of the films was strongly dependent on Ar pressure. To obtain device-quality resistivity without intentional heating during deposition a pressure higher than 1.0 mbar was needed. These films deposited on glass were amorphous, presented a high electron mobility (up to 45 cm2V−1s−1) and a high carrier density (2.9 × 1020 cm−3 for the sample with the highest mobility). The optimum Ar pressure range was found at 1.5–2.3 mbar. However, the resistivity degraded with a moderate annealing temperature in air. Finally, the feasibility of the integration with photovoltaic cells was assessed by depositing on Si substrates passivated by a-Si:H. The film deposited at 1.5 mbar was uniform and amorphous, and the carrier lifetime obtained was 1.22 ms with an implied open circuit voltage of 719 mV after a 215 °C air anneal. The antireflective properties of HPS ITO were also demonstrated. These results show that ITO deposited by HPS is adequate for the research of solar cells with emerging selective contacts.

High-performance perovskite solar cells using the graphene quantum dot–modified SnO2/ZnO photoelectrode

Regardless of the excellent improvement in the assembling of perovskite solar cells (PSCs), the photon-harvesting performance of these devices is inadequate through the disproportionate recombination of generated charge carriers. The improvement of the charge carrier mobility can significantly reduce the recombination and help the perovskite devices reach the theoretical power conversion efficiency (PCE). The modification of charge selective contacts is one of the most effective approaches for reducing the carrier recombination. Herein, we introduce a facile and effective doping engineering approach based on graphene quantum dots (GQDs) for the modification of the SnO2/ZnO bilayer electron transport layer (ETL). A comparative study of perovskite films deposited on SnO2/ZnO layers with altered concentrations of GQDs was employed to significantly enhance the opto-electronic properties. The integration of GQDs into the ETL indicates a potential for improving the charge carrier transporting in PSCs. Overall, the PSC using the 4% GQD-modified ETL yields a PCE of 19.81% with a striking open-circuit voltage (VOC) of 1.17 V. Besides, 4% GQD-modified ETL-based devices enhance the long-term ambient and thermal stability.

Numerical analysis of InP based high efficiency radial junction nanowire solar cell

III-V nanowire (NW) solar cells (SCs) promise a comparable efficiency to that of their planar counterparts with additional advantage of reduced material consumption to cut the manufacturing cost. However, the disadvantage of low minority carrier lifetime due to the large surface-to-volume ratio of NWs degrades its photovoltaic performance to some extent. To overcome this issue, the structure of radial junction instead of axial junction for NWSCs has been used, but in experimental realization, defect density increases in the radial junction structure at the interface of core/shell, resulting in low performance. In this paper, we propose a high performance radial junction NWSC, consisting of p-InP NW coated by Ta 2 O 5 and ITO, and simulate it using Lumerical software. The results show that the use of ITO/Ta 2 O 5 shell over the InP NW as an electron selective contact enhances the absorption of incident photons, which in turn increases efficiency, also providing the condition that the InP required for core can be reduced without sacrificing the ideal current density, leading to a decrease in the fabrication cost. Besides, we investigate and compare the photovoltaic parameters of the structures of ITO/Ta 2 O 5 /p-InP NWSCs with circular and rectangular cross-section in terms of minority carrier life time, doping, and surface recombination velocity (SRV). It is found that circular and rectangular NWSCs with the same filling ratio possess almost the same optimized ideal photo-current such that for the carrier life time of 400 ps and the SRV of less than or equal to 10 4 cm/s at the interface of Ta 2 O 5 /InP, an efficiency as high as ~24.5% and ~25.6% can be achieved for circular and rectangular NWSCs, respectively. • Performance of cylindrical and rectangular InP NW studied using FDTD method. • Optimization of nanostructures is performed in terms of optical Jsc. • Oxide shell ITO/Ta 2 O 5 is used to enhance the absorption and J sc . • Influence of carrier lifetime, doping, and SRV on photovoltaic performance is investigated. • PCE of ~24.5% and ~25.6% is achieved with cylindrical and rectangular NW respectively.

Radiation stability of mixed tin–lead halide perovskites: Implications for space applications

Mixed organic-inorganic halide perovskite solar cells (PSCs) have received considerable attention in recent years for their impressive solar to electrical power efficiency gains and potentially lower material and processing costs for optoelectronic applications. In addition to terrestrial applications, PSCs are of interest to the space power markets for their low cost, low weight, adaptability to flexible architectures, and tolerance to high energy particle irradiation (mainly protons and electrons). Here we investigate the properties of mixed formamidinium-methylammonium tin-lead iodide (FASn)0.6(MAPb)0.4I3 perovskites which lower the lead content as well as the bandgap, making them attractive for the low bandgap absorber material in tandem PSCs. Through current density-voltage (JV) characterization at lower temperatures, majority carrier transport is hindered and a barrier to photogenerated carrier extraction is evident. This is attributed to the thermally induced change of the bandgap of the absorber layer relative to the energy selective contacts in the device. We find that although the architecture used here hinders the performance at temperatures below 225 K, the tolerance to high energy (3.7 MeV) protons is impressive, considerably out-performing commercially available thin-film CIGS. These results suggest further improvements to structural and interface stability as well as lightweight encapsulation could lead to all perovskite flexible tandem arrays deployed for power generation on missions to low Earth orbit, the moon, Mars, and beyond.

In Operando, Photovoltaic, and Microscopic Evaluation of Recombination Centers in Halide Perovskite-Based Solar Cells.

The origin of the low densities of electrically active defects in Pb halide perovskite (HaP), a crucial factor for their use in photovoltaics, light emission, and radiation detection, remains a matter of discussion, in part because of the difficulty in determining these densities. Here, we present a powerful approach to assess the defect densities, based on electric field mapping in working HaP-based solar cells. The minority carrier diffusion lengths were deduced from the electric field profile, measured by electron beam-induced current (EBIC). The EBIC method was used earlier to get the first direct evidence for the n-i-p junction structure, at the heart of efficient HaP-based PV cells, and later by us and others for further HaP studies. This manuscript includes EBIC results on illuminated cell cross sections (in operando) at several light intensities to compare optoelectronic characteristics of different cells made by different groups in several laboratories. We then apply a simple, effective single-level defect model that allows deriving the densities (Nr) of the defect acting as recombination center. We find Nr ≈ 1 × 1013 cm-3 for mixed A cation lead bromide-based HaP films and ∼1 × 1014 cm-3 for MAPbBr3(Cl). As EBIC photocurrents are similar at the grain bulk and boundaries, we suggest that the defects are at the interfaces with selective contacts rather than in the HaP film. These results are relevant for photovoltaic devices as the EBIC responses distinguish clearly between high- and low-efficiency devices. The most efficient devices have n-i-p structures with a close-to-intrinsic HaP film, and the selective contacts then dictate the electric field strength throughout the HaP absorber.

Organic Semiconductor Crystal Engineering for High-Resolution Layer-Controlled 2D Crystal Arrays.

2D organic semiconductor crystals (2DOSCs) have extraordinary charge transport capability, adjustable photoelectric properties, and superior flexibility, and have stimulated continuous research interest for next-generation electronic and optoelectronic applications. The prerequisite for achieving large-area and high-throughput optoelectronic device integration is to fabricate high-resolution 2DOSC arrays. Patterned substrate- and template-assisted self-assembly is an effective strategy to fabricate OSC arrays. However, the film thickness is difficult to control due to the complicated crystallization process during solvent evaporation. Therefore, the manufacturing of 2DOSC arrays with high-resolution and controllable molecular-layer numbers through solution-based patterning methods remains a challenge. Herein, a two-step strategy to produce high-resolution layer-controlled 2DOSC arrays is reported. First, large-scale 2DOSCs with well-defined layer numbers are obtained by a solution-processed organic semiconductor crystal engineering method. Next, the high-resolution layer-controlled 2DOSC arrays are fabricated by a polydimethylsiloxane mold-assisted selective contact evaporation printing technique. The organic field-effect transistors (OFETs) based on 2DOSC arrays have high electrical performance and excellent uniformity. The 2,6-bis(4-hexylphenyl)anthracene 2DOSC arrays-based OFETs have a small variation of 12.5% in mobility. This strategy can be applied to various organic semiconductors and pattern arrays. These demonstrations will offer more opportunities for 2DOSCs for integrated optoelectronic devices.

A comprehensive study of the light soaking effect in ZnS/p-Si heterojunction solar cells

An innovative dopant-free ZnS/p-Si heterojunction solar cell features hole selective WO3 contact were fabricated by thermal evaporation at room temperature. Light soaking effect was observed in the ZnS/p-Si heterojunction solar cells for the first time. The device performance is found to increase with the increasing light soaking times and finally reaches saturation. Besides, when the illumination stops, the power conversion efficiency (PCE) would decrease slightly. Device performance under different light soaking time and preservation time in the dark were investigated. Moreover, different monochromatic illuminations were conducted to further specify the active layer that is responsible for the light soaking effect. The result shows the ZnS layer and the short-wavelength light absorbed in ZnS layer are supposed to be the main reason for the effect. Based on these results, a model was proposed from the point of view of defect states variation in the energy band of ZnS to explain the effect. At last, Deep Level Transient Spectroscopy (DLTS) measurements with different monochromatic illumination were conducted to further verify the proposed model.

Hole selective WOx and V2Ox contacts using solution process for silicon solar cells application

We have prepared solution processed V2Ox and WOx (s-V2Ox and s-WOx) thin films as hole selective contacts for Si solar cell applications. The material properties of s-V2Ox and s-WOx thin films were investigated to shed light on their performance as selective contacts, and their hole selectivity on Si were also characterized. It is found that there is a larger density of oxygen vacancies in s-V2Ox than s-WOx resulting in a larger amount of gap states, but their energy levels in s-V2Ox might not be favourable for carrier transport. We have measured a high work function of 5.17 eV for s-V2Ox and the Fermi level is located above the conduction band suggesting its n-type characteristic. On the other hand, the work function of s-WOx is only 4.71 eV and it is also a n-type semiconductor with the Fermi level situated below the conduction band. From the carrier lifetime studies, both materials are found to exhibit moderate passivation effect on Si and overall they can serve as good hole selective contacts for Si. The optimized power conversion efficiencies of planar s-V2Ox/Si and s-WOx/Si heterojunction solar cells are 10.8% and 9.3% respectively. To the best of our knowledge, the performance of the planar s-V2Ox/Si HSC is better than other reported result for planar configuration using solution process, and this is the first time that the performance of the planar s-WOx/Si HSC is reported.

Carrier gradients and the role of charge selective contacts in lateral heterojunction all back contact perovskite solar cells

Realizing photovoltaic devices that achieve the full potential of the metal halide perovskite material will require improved insight regarding the role of selective contacts and how key interfaces operate when mobile defects are present. However, measuring interface properties in typical device stacks where the perovskite layer is thin and sandwiched between two contacts has been a challenge. Here, we fabricate p-i-n and p-n lateral heterojunctions with nickel oxide/titanium oxide all back contacts, permitting us to employ a comprehensive analysis approach, including ultraviolet and X-ray photoemission spectroscopy (UPS/XPS), angle-resolved X-ray absorption spectroscopy (XAS), Kelvin probe force microscopy (KPFM), surface photovoltage (SPV), hyperspectral imaging (HSI), and time-resolved fluorescence lifetime imaging microscopy (TR-FLIM) to discern the role of selective contacts. Specifically, we tune the selectivity of the contacts, changing the gradient in the carrier concentration across the surface of the active layer, which is connected to carrier extraction at the buried interface, and thus the device functionality. • Charge selective contacts shift the Fermi level in metal halide perovskites (MHPs) • Effect is readily observable because of low defect and doping concentrations in the MHP • Contact selectivity determines carrier extraction across MHP/contact interfaces • Tailoring charge selective contacts to design MHP-based lateral heterojunction devices Metal halide perovskites (MHPs) define an emerging field of novel optoelectronics. For MHP-based applications, such as interdigitated back contact solar cells, the right choice of charge selective contacts remains the principal challenge to overcome; however, relatively few design rules exist because of the unusual defect properties of MHPs. Here, Dunfield et al. employ a range of techniques to discern the role of selective contacts.