Junction Solar Cells Research Articles

Exploring the potential of tin-based perovskite-silicon tandem solar cells through numerical analysis: A pathway to sustainable energy innovation

“Necessity is the mother of invention.” The global imperative to transition from fossil fuels to renewable energy sources, driven by the pressing issue of climate change, highlights the significance of advancing solar energy technologies. While single junction solar cells have reached a peak efficiency of approximately 31 %, the pursuit of higher efficiency has led to the exploration of tandem solar cell architectures, including perovskite-silicon and all-perovskite configurations. However, the widespread use of lead in perovskite structures raises environmental and health concerns. In response to these challenges, this study proposes a novel approach by integrating a tin-based wide bandgap absorber layer with a silicon HIT solar cell (Heterojunction with Intrinsic Layer). The investigation consists of an extensive exploration of six different carrier transport layers (CTL) for the top perovskite layer, considering variations in thickness and defect density. A comprehensive analysis of charge carrier dynamics within the device is conducted to understand the role of defect density in influencing solar cell performance parameters. Simulation results show that the overall tandem device gives an encouraging PCE of 32.12 % in 2 T configuration due to its excellent high value of current density matching 17.63 mA/cm2 and open-circuit voltage of 2.19V. We sincerely hope that our work will open new avenues in the field of Solar Photovoltaics paving the way for future innovations.

Design of Broadband and Wide-angle HLHL Antireflective Coatings for Triple Junction Solar Cells

Design of Broadband and Wide-angle HLHL Antireflective Coatings for Triple Junction Solar Cells

A generalized mathematical modeling and performance analysis of GaAs, m-Si and Ge single - junction solar PV cells

Earlier theoretical approaches have analyzed the performance of semiconductor materials for the influence of temperature and band gap which is implemented in solar photovoltaic systems. This paper investigates the detailed mathematical analysis of single junction semiconductor materials such as Gallium Arsenide (GaAs), mono-crystalline Silicon (m-Si) and Germanium (Ge) solar cells parameters namely, Band gap (Eg), reverse saturation current (Io), shunt resistance (Rsh), Short circuit current (Isc), open circuit voltage (Voc), Fill factor (FF), Maximum Power (Pmax) and Efficiency (Ƞ) for temperature ranging from 273K (≈0°C) to 373K (≈100°C). The optimized cell parameters values are obtained under Air Mass 1.5 Global spectrum (Area = 100cm2 and Irradiance = 100 mW/cm2 for the semiconductor materials (GaAs, m-Si and Ge)) at 300K (≈25°C) are compared to identify the higher efficiency and open circuit voltage. Among the semiconductor materials, the single junction GaAs compound semiconductor material is identified with better efficiency and optimized open circuit voltage. A generalized mathematical model of semiconductor materials is developed using single diode equivalent circuit model under SIMULINK platform and it is used to observe the effect of different temperature, irradiance levels, series resistance and shunt resistance values on the performance of solar cells. The discussion is extended for a 2KW PV array for the semiconductor materials (GaAs, m-Si and Ge) under different temperature and irradiance levels. Evaluating the performance of a PV array, rather than individual cells, provides a more comprehensive understanding of how the chosen semiconductor materials function as part of a larger solar energy system.

34.375 % (33.72 %) -Maximal Efficiencies investigated in New n+(p+)-p(n) CdSe1-xSx, CdSe1-xTex - Crystalline Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures

In two new single n+(p+)−p(n) X(x)-alloy junction solar cells at 300 K, [X(x)≡CdSe1−xSx, CdSe1−xTex], 0≤x≤1, by basing on the same physical model-and-treatment method, as used in our recent works [1, 2], and also other works [3-6], some important results, obtained in the present work, are reported in the following.As noted in Tables 2.1, 3.1, 4.1 and 5.1, the dark carrier-minority saturation current density JoI(oII) decreases slightly with increasing rd(a)-radius for given x, and decreases strongly with increasing x, for given rd(a)-radius. Further, as discussed in Eq. (45), at a same Voc, both JoI(oII) and nI(II) have the same variations for same physical conditions.In particular, at x=0 and for Sn+Cd(Cd+Sn), both n+(p+)-p(n) CdSe1-xSx(Tex)[≡CdSe ] alloys become CdSe-crystals, as observed in Tables 1.1 and 1.2, and therefore, as given in Tables 2.2 (3.2), and 4.2 (5.2), we get the same numerical results of nImax.(IImax.)[=28.184 % (28.310 %)].Further, at x=1 and for Sn+Cd(Cd+Sn), we obtain: (a) in the n+(p+)-p(n) CdSe1-xSx(Tex)[≡CdS ] alloy-junction solar cells, nImax.(IImax.)=34.375 % (33.72 %) and TH=457.1 K (452.6 K), as those given in Tables 2.2 (3.2), and (b) in the +(p+)-p(n) CdSe1-xTex(Tex)[≡CdTe ] alloy-junction solar cells, nImax.(IImax.)=25.676 % (25.443 %), according to: TH=403.6 K (402.4 K), respectively, as those given in Tables 4.2 (5.2).Finally, from above remarks, we could conclude that, in order to obtain the highest efficiencies, the present (CdSe1-xSx, CdSe1-xTex)- crystalline alloy junction solar cells could be chosen rather than the crystalline (CdSe, CdTe)-junction solar cells [1, 2], yielding the highest efficiencies equal to: 26.55 % and 23.69 %, respectively.

Study on P-a-Si:H properties of N-type heterogeneous junction solar cells manufactured by large-area parallel plate PECVD machine

P-type hydrogenated amorphous silicon (P-a-Si:H) plays an important role in heterojunction solar cells. On the one hand, P-a-Si:H processed by plasma enhanced vapor deposition (PECVD) can selectively collect carrier holes on the rear of N-type silicon based heterojunctions with intrinsic thin layer (HJT) solar cells (in this article, the back ride of the cell is P-a-Si:H); On the other hand, the ohmic contact between P-a-Si:H and conductive ITO film is beneficial for hole transport. Therefore, the performance of P-a-Si:H has very significant impact on the property of HJT solar cells. The electrical conductivity, impurity activation energy, and passivation performance of silicon wafer surface are the core performance indicators of P-a-Si:H materials themselves. In this paper, we systematically research the optimal RF power density, doping concentration (diborane doped), hydrogen dilution ratio and plate spacing for the growth process of P-a-Si:H using a self-developed large-area parallel plate PECVD equipment (Jincheng Machine). The results show that the P-a-Si:H has an electrical conductivity of 1.27 × 10−3 S/cm and an activation energy of 251 meV, and the maximum mass production efficiency of the HJT solar cell is 25.21%, Voc is 741 mV and Jsc is 41.57 mA/cm2.

34.151 % (33.93 %) - Maximal Efficiencies investigated in New n+(p+) - p(n) CdTe1-xSx, CdTe1-xSex - Crystalline Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures

In two new single n+(p+)−p(n) X(x)-alloy junction solar cells at 300 K, [X(x)≡CdTe1−xSx, CdTe1−xSex],0≤x≤1, by basing on the same physical model-and-treatment method, as used in our recent works [1, 2], and also other works [3-11], some important results, obtained in the present work, are reported in the following.As noted in Tables 2.1, 3.1, 4.1 and 5.1, the dark carrier-minority saturation current density

Temperature-dependent electronic, optical, and solar cell device properties of AlAs and AlSb semiconductors and their p-n homojunctions

AlSb and AlAs have attracted renewed interest in recent years as promising photovoltaic (PV) materials due to significant light absorption, eco-friendliness, and low cost. Here, density functional theory (DFT) in combination with the non-equilibrium Green's function method (NEGF) has been used to compute the temperature-dependent PV parameters of nanoscale AlSb and AlAs p-n junction solar cell devices. In particular, the influence of electron-phonon coupling (EPC) and spin-orbit coupling (SOC) on the PV properties of these devices is investigated. Our results highlight the importance of inclusion of EPC in evaluating the ab initio PV properties of p-n junctions at finite temperatures. At non-zero temperatures, the PV parameters can differ significantly compared to those at zero temperature due to phonon-assisted tunnelling of charge carriers across the p-n junction. In particular, the mobility of low-effective-mass carriers at the p-n junction is found to be enhanced by phonon scattering, which in turn results in improved PV transport properties. The short-circuit current (Jsc) at 300 K proved to be 21.7% (16.2%) higher for AlSb (AlAs) than that at 0 K. On the other hand, the open-circuit voltage (Voc) at 300 K proved to be 19.1% (16.7%) lower for AlSb (AlAs) than that at 0 K. Jsc is higher in AlSb than in AlAs due to higher phonon-influenced mobility of low-effective-mass carriers. Overall, our study strongly suggests the importance of inclusion of EPC and hence phonon scattering in the first-principles quantitative determination of PV parameters of solar cells. The estimates obtained in this study may be utilized as input ab initio parameters in continuum-model-based multi-scale simulations of AlSb and AlAs p-n homo-junction solar cells.

Metasurface absorber based single junction thin film solar cell exceeding 30% efficiency.

In this article, we report, as per our knowledge, for the first time, a thin film single junction solar cell with a metasurface absorber layer directly incorporated. We have used an interconnected dual inverted split ring resonator pattern in the InAsP absorber layer. The structure eliminated patterns of conventional metals, such as silver, aluminum, and gold, from the active layer, a common drawback in conventional solar absorbers, hindering their direct integration into solar cells. Optical simulation results show a peak ideal short circuit current density of 76.23mA/cm2 for the meta-absorber structure under solar illumination. This current is the highest among previously reported absorbers based on Group IV materials and III-V compounds, overcoming the low solar absorption of such metasurfaces. The final proposed solar cell structure combines this meta-absorber layer with traditional efficiency enhancement methods namely anti-reflecting coating, textured back reflector, and transparent top electrode. This novel single junction structure shows a solar absorption efficiency of 97.86% and a power conversion efficiency of 30.87%, the highest for III-V solar cells. Our device proves the ability of metasurface absorber layers to produce high-efficiency solar cells and is expected to pave the way for integrating novel meta-devices into state-of-the-art photovoltaic devices, aiding the global transition towards clean energy sources.

Remarkable enhancement of graphene/Si Schottky junction solar cell performance with effective chemical treatments

Graphene has been employed in the preparation process of solar cells due to its unique properties. It has been combined with silicon (Si) substrates for preparing the top window structure of a graphene/n-Si Schottky junction solar cell. However, the usage of the mono-graphene layer results in a low fill factor of prepared samples. In addition, the residue of PMMA is one more reason for the low fill factor. Another disadvantage of reported devices is the poor stability of doped devices under ambient conditions. In this work, 2 low-cost and simple chemical treatments are employed to eliminate the residue of PMMA after the wet transfer procedure of graphene. Besides, the fill factor is significantly developed by transferring more than a residue-free graphene layer. An efficiency of 6% is obtained after preparing devices with 3 graphene layers, and the recorded efficiency of 14.2% is attained by the HNO3 dopant. Additionally, doped devices show excessive stability for 2 months under ambient conditions, retaining around 96% of their initial efficiency. We attribute this development to the donation process of electrons achieved by chemical treatments to graphene. This work presents an approach for providing low-cost, simple, high performance and stable graphene/Si Schottky solar cells.

Performance evaluation of 2D MoS2-based solar cells and realization of transparent ultra-thin devices

Molybdenum disulfide (MoS2) is an alternate absorber layer in 2D solar cells owing to its potential of proficient sunlight harvesting. The optimum electrical and optical properties of MoS2 validate it as a suitable photovoltaic absorber material. This work investigates the performance of 2D (and multi-layer) MoS2-based vertically stacked solar cell by numerical simulation process using one dimensional solar cell capacitance simulator (SCAPS). Two device configurations based on Schottky junction (ITO/n-MoS2/Au) and pn junction (ITO/n-MoS2/p-MoS2/Au) have been theoretically analyzed. The feasibility of ultra-thin transparent solar cells is also demonstrated, which is motivating from a technological outlook. Initially, the properties of the active layers are optimized to give the highest performance. The findings are explained on the basis of band alignment between the electrodes and the different layers. The potential barrier developed at the interface of different materials governs the output of the cells. The calculations forecast the material properties, which need to be tuned to fabricate solar cells with enhanced efficiency. After optimization, the highest efficiency obtained for single n-MoS2-based solar cell is 10.22%, while for the pn junction solar cell it is 16.86%. The optimized cells exhibit high open circuit voltages of ∼1.2 V, which is an essential factor for commercial realization of solar cells. Lastly, the performance of transparent solar cells based on thin 2D MoS2 films has been predicted which showcases the efficiency in the range of 0.78%–4.36%. These homo-junction device investigations of solely MoS2 layer along with employment of a strict control on the defects during deposition and fabrication of MoS2-based solar cells can ensure better performance of the device. Thus, it can open ways to develop next generation feasible solar cells with higher power density as compared to existing technology.

21.2% GaAs Solar Cell Using Bilayer Electron Selective Contact

GaAs remains one of the crucial materials for solar cell applications as it boasts the world's highest efficiency single‐junction solar cells. However, their high cost limits their widespread terrestrial applications. Traditional GaAs solar cells require a complex stack of doped junctions, which can only be grown using epitaxy, which is a very costly technique. Herein, a nonepitaxial bilayer of ZnO and TiO2 as electron‐selective contact is studied. It is shown that a bilayer selective contact can achieve very high performance through interface band engineering and a reduction of the barrier for electron transfer. 21.2% efficient solar cells is achieved, with Voc of 1.04 V, Jsc of 26.13 mA cm−2, and a fill factor of 77.8%. The Voc reported in the article is comparable to the highest Voc reported for substrate‐based GaAs solar cells of 1.075 V. An experimental loss analysis shows that the device is mainly limited by series and shunt resistance and reflection losses, both of which can further be minimized by optimization of the fabrication process. The results presented will be very useful for the further development of cheaper GaAs solar cells, whereas the bilayer selective contact concept can be implemented for other kinds of solar cells.

Study and simulation of GaInP single junction solar cell

This study aims to improve the electrical performances of the GaxIn1-xP single junction solar cell. To this objective, a single-junction solar cell GaxIn1-xP has been simulated with different doping concentrations and thicknesses of the emitter and base region in order to improve its conversion efficiency. The simulations have been done taking into account the optical, electrical and physical properties of the GaxIn1-xP according to the indium composition. The physical models such as the radiative, Auger and Shockley–Read–Hall (SRH) recombination were also considered. The optimized single junction Ga0.04In0.96P (1.39 eV) solar cell structure achieved, showed, under standard conditions (1-sun, AM1.5, 300 K), a maximum conversion efficiency of 23.73%. Moreover, the effects of the thickness and the doping concentration of each region on the electrical parameters of the Ga0.04In0.96P solar cell were also studied.

Simulation study of Perovskite/Si Monolithic Multijunction Solar Cell

The utilization of perovskite and crystalline-silicon (c-Si) light absorbers in multijunction solar cells presents an exciting opportunity to surpass the efficiency limit of the industry's leading single-junction c-Si solar cells. In this work, we used the Solar Cell Capacitance Simulator (SCAPS-1D) to simulate a monolithic tandem junction solar cell. The solar cell consists of two types of materials: low bandgap and high bandgap. These are layers of perovskites and Si, divided by a window layer of zinc oxide (ZnO), a buffer layer of cadmium sulfide (CdS), a recombination layer of Spiro-MeOTAD/silicon, and a heavily doped back surface field layer formed from n++Si to prevent recombination at the back surface. The impact of di fferent series and shunt resistances, as well as perovskite layer thickness and bandgap, on solar cells' photovoltaic performance has been investigated.

High-performance radial junction solar cells on ZnO coated stainless steel with excellent flexibility and durability

High flexibility and industrial compatibility are the key factors for developing large-scale lightweight, wearable, and portable thin film flexible solar cells. Here, a rather flexible and mechanically durable three-dimensional (3D) radial junction (RJ) solar cell has been directly constructed over discrete standing Si nanowires (SiNWs), upon flexible ZnO-coated stainless steel (SS) foil substrates. The ZnO layer deposited on the SS surface can optimize the density of SiNWs to improve the optoelectronic performance. A power conversion efficiency of 6.01% has been accomplished, with open-circuit voltage and photo-current density of 0.76 V and 12.87 mA/cm2, respectively. Remarkably, the outstanding mechanical stability of these RJ devices has been recorded, which can sustain > 4000 cycles of large bending to a radius of 2.5 mm, with only a 7% efficiency decrease. Note that the one-pump-down fabrication procedure of this 3D nanostructure RJ cells upon flexible ZnO-coated SS substrates is compatible with the industrial-mainstream Roll-to-Roll technology, holding thus a strong promise to establishing a simple and low-cost strategy for high-performance and durable flexible photovoltaics.

Maximal Efficiencies in New Single GaAs1−xTex-Alloy Junction Solar Cells at 300 K

In single n+(p+) − p(n) [XX(xx) ≡ GaAs1−xTex]-alloy junction solar cells at 300 K, 0 ≤ x ≤ 1, by basing on the same physical model and the same treatment method, as those used in our recent work (Van Cong, 2023), we will investigate the highest (or maximal) efficiencies, ηImax.(IImax.), obtained at the open circuit voltage Voc(=VocI(ocII)), according to highest hot reservoir temperatures TH(K), obtained from the Carnot efficiency theorem, being proved by entropy law. Here, one first remarks that, with increasing x=(0, 0.5,1), (i)- from Table 3, for the single n+ − p X(x)-alloy junction solar cell and for given rSn(Cd)-radius, for example, ηImax. (↗)= 31.14%, 31.55%, 32.11%, according to TH(K) = 435.7, 438.3, 4444 . 99, at VocI(V) = 1.07, 1.07, 11. 00 , respectively, while, (ii)- from Table 5, for the single p+ − n X(x)-alloy junction solar cell and for givenrCd(Sn)-radius, for example, ηIImax. (↘)= 33.04%, 32.65%, 32.51%, according to TH(K) = 444444. 00, 445.4, 444.5, at VocII(V)[> VocI(V)] = 1.20, 1.19, 1.18, respectively, suggesting that suchηImax.(IImax.)-and-TH variations depend on the VocII(V)[> VocI(V)] − values. Then, as given in Table3, for x = 0 and for rd(a) = rTe(Mg), one gets: ηI =23.48 % and 29.71 % at Voc = 0.98 V and 1.1272
 V, respectively, which can also be compared with the corresponding results, obtained for the single-junction GaAs thin-film solar cell, 22.08 % and 29.71 %, with relative deviations in absolute values, 6.34
 % and 2.1 %, and given respectively by Moon et al. (2016) and Green et al. (2022). As a result, in orderto obtain the highest efficiencies, the single GaAs1−xTex-alloy junction solar cells could be chosen ratherthan the single crystalline GaAs-junction solar cell.

Maximal Efficiencies in New Single GaAs 1−x Sb x-Alloy Junction Solar Cells at 300 K

In single n+(p+)−p(n) [X(x)≡GaAs1−xSbx]-alloy junction solar cells at 300 K, 0≤x≤1, by basing on the same physical model and the same treatment method, as those used in our recent work (Van Cong et al., 2023; Van Cong, 2023), we will investigate the highest (or maximal) efficiencies, ηImax.(IImax.), obtained at the open circuit voltage Voc(=VocI(ocII)), according to highest hot reservoir temperatures TH(K), obtained from the Carnot efficiency theorem, being proved by entropy law. Here, one first remarks that, with increasing x=(0, 0.5, 1), (i)- from Table 3, for the single n+−p X(x)-alloy junction solar cell and for given rSn(Cd)-radius, for example, ηImax.(↘)= 31.14%, 28.72%, 25.36%, according to TH(K)=

Maximal Efficiencies in New Single GaAs(1−x) P(x) - Alloy Junction Solar Cells at 300 K

In single n+(p+) − p(nn) [X(x) ≡ GA1−xPx]-alloy junction solar cells at 300 K, 0 ≤ xx ≤ 1, by basing on the same physical model and the same treatment method, as those used in our recent works (Van Cong, 2024), we will also investigate the highest (or maximal) efficiencies, ηImax .(IImax.) at the open circuit voltageVos(= Vos1 (os2 ),according to highest hot reservoir temperatures TH(K), obtained from the Carnot efficiency theorem, which was demonstrated by the use of the entropy law. Here, some concluding remarks are given in the following. (i)-First, with increasing x=(0, 0.5, 1), from Table 3, obtained for the single n+ − p X(x)-alloy junction solar cells, and for given rSn(Cd)-radius, for example, one obtains: ηImax (↗)= 31.18%, 33.495%, 35.99%, according to TH(K) = 435.9, 451.1, 468.7, at Vos (V) = 1.07, 1.06, 1.05, respectively. (ii)- Secondly, with increasing x=(0, 0.5, 1), from Table 5, obtained for the single p+ − n X(x)-alloy junction solar cells, and for given rCd(Sn)-radius, for example, one gets: ηηIImax (↘)= 33.05%, 31.95%, 31.37%, according to TH(K) = 448.0, 440.9, 437.1, at Vos (V)[>Vos(V)] = 1.20, 1.15, 1.12, respectively, suggesting that such ηImax .(IImax .)-and-TH variations dependon Vos(V)[> Vos (V)] − values. Then, in particular, as given in Table 3, for x = 0 and (rda ) =(pt), one gets: ηI =23.48 % and 29.76 % at Vos= 0.98 V and 1.1272 V, respectively, which can be compared with the corresponding results obtained by Moon et al. (2016) and Green et al. (2022) for the single-junction GaAs thin-film solar cell, 22.08 % and 29.71 %, with relative deviations in absolute values, 6.34 % and 0.17 %. Finally, one notes that, in order to obtain the highest efficiencies, the single GaAs1−x Px-alloy junction solar cells could be chosen rather than the single crystalline GaAs-junction solar cell.

Structural and optical properties of phosphorous doped nanocrystalline silicon deposited using a VHF PECVD process for silicon heterojunction solar cells and optimization of a simple p-n junction cell using SCAP-1D tool.

Initially hydrogenated silicon (Si:H) thin films have been deposited using a plasma-enhanced chemical vapor deposition technique (PECVD) using silane (SiH4) as a precursor gas diluted in an inert gas argon (Ar) environment. Subsequently phosphine gas (PH3) was used as the n-type dopant and the deposition was carried out at a fixed substrate temperature of 200 °C. The PH3 flow rate was varied in the range of 0-1 sccm. The effect of PH3 flow rates on optical, electrical, and structural properties of hydrogenated amorphous and micro/nanocrystalline silicon films has been investigated and detailed analysis is presented. These films may find application in heterojunction solar cells as an emitter layer. Further, a crystalline silicon (c-Si) based simple p-n junction solar cell is simulated using an SCAP-1D tool to observe the effect of layer thickness and doping density on solar cell parameters.

Simulation and optimization of GaAs1-xPx/Si1-yGey/Ge triple junction solar cells

This paper focuses on studying and simulating a GaAs1-xPx/Si1-yGey/Ge triple-junction solar cell structure. First, the strain and the bandgap energy associated to the SiGe layer have been studied. The optimal germanium concentration is 0.88 with a strain around 0.45%. Then, the phosphor concentration effect on the strain and the bandgap energy of the upper layer GaAs1-xPx/Si0.12Ge0.88 has been optimized. At room temperature, the optimal output parameter reach Jsc=34.41mA/cm2 , Voc=1.27V, FF=88.42% and η=38.45% for an absorber thickness of 4.5µm and x=0.47, with a strain that doesn’t exceed 1.5%. This study has enabled us to design a high-efficiency, low cost 3J solar cell.

Treasure-bowl style bifunctional site in cerium-tungsten hetero-clusters for superior solar-driven hydrogen production.

Electrochemical water splitting powered by renewable energy sources hold potential for clean hydrogen production. However, there is still persistent challenges such as low solar-to-hydrogen conversion efficiency and sluggish oxygen evolution reactions. Here, we address the poor kinetics by studying and strengthening the coupling between Ce and W, and concurrently establishing Ce-W bi-atomic clusters on P,N-doped carbon (WN/WC-CeO2-x@PNC) with a "treasure-bowl" style. The bifunctional active sites are established using a novel and effective self-sacrificial strategy involving in situ induced defect formation. In addition, by altering the coupling of the W(d)-N(p) and W(d)-Ce(f) orbitals in the WN/WC-CeO2-x supramolecular clusters, we are able to disrupt the linear relationship between the binding energies of reaction intermediates, a key to obtain high catalytic performance for transition metals. Through the confinement of the WN/WC-CeO2-x composite hetero-clusters within the sub-nanometre spaces of hollow nano-bowl-shaped carbon reactors, a stable and efficient hydrogen production via water electrolysis could be achieved. When assembled together with a solar GaAs triple junction solar cell, a solar-to-hydrogen conversion efficiency of 18.92% in alkaline media could be realized. We show that the key to establish noble metal free catalysts with high efficiency lies in the fine-tuning of the metal-metal interface, forming regions with near optimal adsorption energies for the reaction intermediates participating in water electrolysis.