P-n Junction Research Articles

Narrow Bandgap Metal Halide Perovskites for All-Perovskite Tandem Photovoltaics.

All-perovskite tandem solar cells are attracting considerable interest in photovoltaics research, owing to their potential to surpass the theoretical efficiency limit of single-junction cells, in a cost-effective sustainable manner. Thanks to the bandgap-bowing effect, mixed tin-lead (Sn-Pb) perovskites possess a close to ideal narrow bandgap for constructing tandem cells, matched with wide-bandgap neat lead-based counterparts. The performance of all-perovskite tandems, however, has yet to reach its efficiency potential. One of the main obstacles that need to be overcome is the─oftentimes─low quality of the mixed Sn-Pb perovskite films, largely caused by the facile oxidation of Sn(II) to Sn(IV), as well as the difficult-to-control film crystallization dynamics. Additional detrimental imperfections are introduced in the perovskite thin film, particularly at its vulnerable surfaces, including the top and bottom interfaces as well as the grain boundaries. Due to these issues, the resultant device performance is distinctly far lower than their theoretically achievable maximum efficiency. Robust modifications and improvements to the surfaces of mixed Sn-Pb perovskite films are therefore critical for the advancement of the field. This Review describes the origins of imperfections in thin films and covers efforts made so far toward reaching a better understanding of mixed Sn-Pb perovskites, in particular with respect to surface modifications that improved the efficiency and stability of the narrow bandgap solar cells. In addition, we also outline the important issues of integrating the narrow bandgap subcells for achieving reliable and efficient all-perovskite double- and multi-junction tandems. Future work should focus on the characterization and visualization of the specific surface defects, as well as tracking their evolution under different external stimuli, guiding in turn the processing for efficient and stable single-junction and tandem solar cell devices.

Fabrication of ZnO Scaffolded CdS Nanostructured Photoanodes with Enhanced Photoelectrochemical Water Splitting Activity under Visible Light.

CdS, characterized by its comparatively narrow energy band gap (∼2.4 eV), is an appropriate material for prospective use as a photoanode in photoelectrochemical water splitting. Regrettably, it encounters several obstacles for practical and large-scale applications, including issues such as bulk carrier recombination and diminished conductivity. Here, we have tried to address these challenges by fabricating a novel photoelectrode (ZnO/CdS) composed of one-dimensional ZnO nanorods (NRs) decorated with two-dimensional CdS nanosheets (NSs). A facile two-step chemical method comprising electrodeposition along with chemical bath deposition is employed to synthesize the ZnO NRs, CdS NSs, and ZnO/CdS nanostructures. The prepared nanostructures have been investigated by UV-visible absorption spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy. The fabricated ZnO/CdS nanostructures have shown enhanced photoelectrochemical properties due to the improvement of the semiconductor junction surface area and thereby enhanced visible light absorption. The incorporation of CdS NSs has been further found to promote the rate of the charge separation and transfer process. Subsequently, the fabricated ZnO/CdS photoelectrodes achieved a photocurrent conversion efficiency 3 times higher than that of a planar ZnO NR photoanode and showed excellent performance under visible light irradiation. The highest applied bias photon-to-current conversion efficiency (% ABPE) of about ∼0.63% has been obtained for the sample with thicker CdS NSs on ZnO NRs with a photocurrent density of ∼1.87 mA/cm2 under AM 1.5 G illumination. The newly synthesized nanostructures further demonstrate that the full photovoltaic capacity of nanomaterials is yet to be exhausted.

Universal silicon ring resonator for error-free transmission links

We report the design, fabrication, and characterization of a universal silicon PN junction ring resonator for C band error-free communication links operated up to 50 Gb/s with co-designed optical modulation and detection performance. The universal p-n junction ring device shows co-designed detection responsivity up to 0.84 A/W, in conjunction with a modulation efficiency of ∼4 V·mm and >8 dB optical modulation extinction ratio, enabling C band 50 Gb/s NRZ communication link with a bit error rate ≤3×10−12. Individually, the speed of modulation and detection is measured up to 112 Gb/s and 80 Gb/s, respectively. The principle of co-designing the PN junction ring modulator and detector performance required for error-free communication links can significantly ease the fabrication yield challenges of ring structures by reducing the number of types of devices. The principle can also be applied to O band wavelengths. To the best of our knowledge, for the first time, a device of this type has achieved both error-free modulation and detection operation up to 50 Gb/s in the C band individually or in conjugation as an error-free communication link, which paves the way to realize a >1.6 Tb/s all-silicon WDM-based error-free optical transceiver link in the future and is essential for future programmable photonics circuits.

Mixed tin-lead perovskites with balanced crystallization and oxidation barrier for all-perovskite tandem solar cells

Mixed tin-lead perovskite solar cells have driven a lot of passion for research because of their vital role in all-perovskite tandem solar cells, which hold the potential for achieving higher efficiencies compared to single-junction counterparts. However, the pronounced disparity in crystallization processes between tin-based perovskites and lead-based perovskites, coupled with the easy Sn2+ oxidation, has long been a dominant factor contributing to high defect densities. In this study, we propose a multidimensional strategy to achieve efficient tin-lead perovskite solar cells by employing a functional N-(carboxypheny)guanidine hydrochloride molecule. The tailored N-(carboxypheny)guanidine hydrochloride molecule plays a pivotal role in manipulating the crystallization and grain growth of tin-lead perovskites, while also serving as a preservative to effectively inhibit Sn2+ oxidation, owing to the strong binding between N-(carboxypheny)guanidine hydrochloride and tin (II) iodide and the elevated energy barriers for oxidation. Consequently, single-junction tin-lead cells exhibit a stabilized power conversion efficiency of 23.11% and can maintain 97.45% of their initial value even after 3500 h of shelf storage in an inert atmosphere without encapsulation. We further integrate tin-lead perovskites into two-terminal monolithic all-perovskite tandem cells, delivering a certified efficiency of 27.35%.

Monolithic Two-Terminal Tandem Solar Cells Using Sb2S3 and Solution-Processed PbS Quantum Dots Achieving an Open-Circuit Potential beyond 1.1 V.

Multijunction solar cells have the prospect of a greater theoretical efficiency limit than single-junction solar cells by minimizing the transmissive and thermalization losses a single absorber material has. In solar cell applications, Sb2S3 is considered an attractive absorber due to its elemental abundance, stability, and high absorption coefficient in the visible range of the solar spectrum, yet with a band gap of 1.7 eV, it is transmissive for near-IR and IR photons. Using it as the top cell (the cell where light is first incident) in a two-terminal tandem architecture in combination with a bottom cell (the cell where light arrives second) of PbS quantum dots (QDs), which have an adjustable band gap suitable for absorbing longer wavelengths, is a promising approach to harvest the solar spectrum more effectively. In this work, these two subcells are monolithically fabricated and connected in series by a poly(3,4-ethylene-dioxythiophene) polystyrene sulfonate (PEDOT:PSS)-ZnO tunnel junction as the recombination layer. We explore the surface morphology of ZnO QD films with different spin-coating conditions, which serve as the PbS QD cell's electron transport material. Furthermore, we examine the differences in photogenerated current upon varying the PbS QD absorber layer thickness and the electrical and optical characteristics of the tandem with respect to the stand-alone reference cells. This tandem architecture demonstrates an extended spectral response into the IR with an open-circuit potential exceeding 1.1 V and a power conversion efficiency of 5.6%, which is greater than that of each single-junction cell.

Interface engineering by constructing vertical junction for reduced noise and improved sensitivity in 2D photodetector

Two-dimensional (2D) materials have been widely demonstrated as promising candidates for next generation photodetectors, while the noticeable channel current is still a limiting factor for photodetection sensitivity. In this work, the interface engineering has been developed by constructing a vertical pn and Schottky junction in the 2D WS2 channel, resulting in a reduced dark current and noise spectral density, significantly improving the sensitivity. Specifically, the WS2 bottom surface is coupled with p-type tellurium (Te) nanoribbon and gold (Au) stripes, thus a vertical pn and Schottky junction can be constructed at WS2/Te and WS2/Au interface, respectively. In both device architectures, the dark current and electric noise are much suppressed due to the formation of depletion region in WS2 channel. Meanwhile, the out-of-plane built-in electric field at junction can facilitate the separation of photo-excited electron–hole pairs, which subsequently yields a faster temporal response. For the WS2/Au device, the incident light can be reflected by the bottom Au and propagate through the WS2 layer again, further boosting the photo-absorption, thus the photodetection sensitivity. The engineered WS2 photodetectors exhibit the noise spectral density as low as 5.36 × 10−14 A Hz−1/2 and high specific detectivity (D*) up to 1.12 × 1011 Jones, which has one–two orders of magnitude improvement compared to the pristine device. This work provides an effective and universal interface engineering strategy to achieve low noise and high sensitivity in 2D photodetectors.

High-efficiency TOPCon solar cell with superior P + and P++ layer via one-step processing

The boron diffusion process in the front field of N-type tunnel oxide passivated contact (TOPCon) solar cells is crucial for PN junction formation and the creation of a selective emitter. This study presents a theoretical model of boron diffusion in silicon using molecular dynamics. The research examines the mean square displacement and diffusion coefficient of boron atoms at varying temperatures, confirming their diffusion behavior. The simulations indicate predominant boron diffusion in the z-direction within the silicon matrix, with the diffusion depth being temperature dependent. The optimal temperature range for boron diffusion in silicon is identified as 950 °C to 1050 °C. Using boron-doped silicon paste and boron trichloride as dopants, thermal diffusion experiments were conducted to fabricate the front-field PN junction (p+ layer) and selective emitter (p++ layer) by one step. Subsequent processing and performance evaluation were performed on a production line. Experimental findings reveal a decrease in boron diffusion at higher temperatures, reduced sheet resistance, increased doping concentration, and deeper junction formation. The ideal boron concentration in the p+ layer is 8.68 × 1018 atom/cm3 with a depth of 0.53 μm, while the p++ layer is 2.35 × 1019 atom/cm3 and 0.82 μm. The efficiency of the optimized TOPCon + cell production line reaches up to 25.17 %, marking an improvement of 0.23 % over the standard cell production line. This research contributes to elucidating the mechanism of boron diffusion and offers insights for enhancing the efficiency of TOPCon solar cells.

Electrical properties and band alignments of Sb2Te3/Si heterojunctions, low-barrier Sb2Te3/n-Si and high-barrier Sb2Te3/p-Si junctions

We investigated the electrical junction properties of the layered Sb2Te3 film formed on Si substrates. The current−voltage characteristics of the Sb2Te3/n-Si heterojunction showed an ohmic properties, whereas the Sb2Te3/p-Si heterojunction exhibited rectifying properties with a high barrier height of 0.77 eV. The capacitance−voltage characteristics of MOS capacitors with the Sb2Te3 electrode indicated an effective work function of 4.44 eV for the Sb2Te3 film. These findings suggest that the Sb2Te3/Si heterostructure possesses a low conduction band offset, as inferred from the temperature dependence of the current−voltage characteristics of the Sb2Te3/n-Si.

Analytical model for the drain and gate currents in silicon nanowire and nanosheet MOS transistors valid between 300 and 500 K

AbstractThis work presents an analytical model for the drain and gate currents of silicon nanowire and nanosheet MOS transistors valid in all operating regions in the temperature range from 300 to 500 K. Analytical models for the tunneling components as well as for the reversely biased drain‐to‐channel PN junction are presented. Also, the models accounting for the necessary modifications in the silicon physical quantities for high‐temperature operation, such as the maximum carrier mobility, the bandgap, and the intrinsic carrier concentration, are presented. The proposed model uses a single set of parameters, extracted at room temperature, to describe the high‐temperature operation of silicon nanowire MOSFETs. The model is validated with comparisons between modeled and experimental results for devices with different fin widths and operating temperatures, with good agreement.

Carrier transport engineering in a polarization-interface-free ferroelectric PN junction for photovoltaic effect

The carrier transport performances play key roles in the photoelectric conversion efficiency for photovoltaic effect. Hence, the low carrier mobility and high photogenerated carrier recombination in ferroelectric materials depress the separation of carriers. This work designs a ferroelectric polarization-interface-free PN junction composed with P-type semiconductor BiFeO3 (BFO) derived from the variable valence of Fe and N-type semiconductor BiFe0.98Ti0.02O3 (BFTO) through Ti donor doping. The integration of the ferroelectricity decides the PN junction without polarization coupling like the traditional heterojunctions but only existing carrier distribution differential at the interface. The carrier recombination in PN junction is significantly reduced due to the driving force of the built-in electric field and the existence of depletion layer, thereby enhancing the switching current 3 times higher than that of the single ferroelectric films. Meanwhile, the carrier separation at the interface is significantly engineered by the polarization, with open circuit voltage and short circuit current of photovoltaic effect increased obviously. This work provides an alternative strategy to regulate bulk ferroelectric photovoltaic effects by carrier transport engineering in the polarization-interface-free ferroelectric PN junction.

Automatic optimal design of field plate for silicon on insulator lateral double‐diffused metal oxide semiconductor using simulated annealing algorithm

AbstractField plate (FP) technology has been widely used due to its simple structure and process compatibility. Through introducing the interface charge to suppress the electric field peak at the junction region, the breakdown performance can be improved. However, designing an appropriate FP for semiconductor power devices is challenging and time‐consuming. In this paper, the authors propose a fully automated FP optimal design method based on simulated annealing algorithm (SA) for silicon on insulator lateral double‐diffused metal oxide semiconductor. By using an automatic iterative process to obtain the minimum value of the objective function, the parameters related to the FP can be effectively provided. Numerical results show that when the breakdown occurs at the N+N or PN junction, the breakdown voltage can be optimized by an average of 18.6% and 45.5%, respectively. Moreover, compared with the existing methods, the proposed approach is highly efficient with a runtime that does not exceed 12 s. The authors believe that this method can greatly accelerate the power device design process.

Effect of Ag layer thickness on lateral photovoltaic mechanisms in Ag/p-Si structures

The lateral photovoltaic effect (LPE) has been widely employed in optoelectronic devices for its high sensitivity and broadband responsivity. Typically, the physical mechanism of LPE is based on Schottky junction or PN junction. In this article, we present experimental evidence for multiple lateral photovoltaic mechanisms in Ag/p-Si structures and demonstrate the dominant mechanism of LPE can be converted from surface states to the Schottky barrier or localized surface plasmon resonances (LSPRs) by tuning the Ag thickness. We believe this experimental result extends the knowledge into the underlying mechanisms of LPE and presents a wide range of possibilities for the further development of LPE-based photodetectors.

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.

Research on the electro-magnetic protection technique of SCB bridge based on vertical punch through PN junction

Pyrotechnic device is the key initiating component of weapon system, and its function reliability will directly affect the triggering of detonation and actuation mechanism. In order to enhance the survival ability of pyrotechnic device in intricate electromagnetic interference environment, it is necessary to carry out in-depth research on the electromagnetic protection technique of pyrotechnic device. In this paper, a new electromagnetic protection circuit based on vertical punch through PN junction device is proposed, which monolithically integrates the circuit with polysilicon semiconductor bridge on a single chip. The Electro-static Discharge (ESD) test was carried out according to the method specified by standard electrostatic standard 500 pF/500 Ω/25 kV, and the ESD capability of the proposed new chip was not less than 25 kV. Compared with the electromagnetic protection circuit by transient voltage suppressor diode based on lateral punch through junction device structure, the new chip increases the effective junction area of PN junction, reduces the current density, and increases the current conduction ability and electrostatic roughness of the diode. The new chip has a larger diode effective junction capacitance, which not only improves the ESD capability but also improves the RF protection capability at the same time.

Ab initio study of p- and n-type doping of two-dimensional MoO2: investigation of a pn-homojunction

Based on density functional theory, we studied the effect of p- and n-type doping on the structural and electronic properties of MoO2 monolayers and bilayers. We used niobium (Nb) and nitrogen (N) as p-type dopants, and technetium (Tc) and fluorine (F) as n-type dopants through atomic substitutions. Our study shows that the presence of a substituent in the 4 × 4 supercell of MoO2 leads to a slight distortion and negligible modification of the lattice parameter. Both p- and n-type doped monolayers exhibit a metallic character. The bilayers obtained by vertically stacking n-p doped monolayers all exhibit a metallic character, as their band diagrams do not show a band gap. The study of their charge difference highlights a physisorption phenomenon. This type of material, which features a nucleophilic site in the p-doped region and an electrophilic site in the n-doped region, is a promising candidate for catalysis. When n-type and p-type doped monolayers are horizontally joined, the resulting stack exhibits a semi-conductor behavior.The special feature of this stacking is that we obtain a true pn junction, that is a space charge zone associated with a potential jump. For its application in infrared junction diodes, we have demonstrated both quantitatively and qualitatively the existence of a potential jump at the junction.

Characterization of a Heterojunction Silicon Solar Cell by Means of Impedance Spectroscopy.

Impedance spectroscopy provides relevant knowledge on the recombination and extraction of photogenerated charge carriers in various types of photovoltaic devices. In particular, this method is of great benefit to the study of crystalline silicon (c-Si)-based solar cells, a market-dominating commercial technology, for example, in terms of the comparison of various types of c-Si devices. This study investigates the dark and light electrophysical characteristics of a heterojunction silicon solar cell fabricated using plasma-enhanced chemical vapor deposition. The measurements are performed at various applied biases, enabling the determination of complex resistance, characteristic time, capacitive response and impurity concentration within the semiconductor junction and to correlate them with the device performance. In addition, the impedance spectra of the studied cell were investigated as a function of temperature. Studies of the frequency and temperature dependences of capacitance do not reveal a significant presence of thermally activated centers of free carrier capture, concomitant with a very small value of the activation energy extracted from an Arrhenius-type analysis. This leads to a conclusion that these centers are likely not impactful on the device operation and efficiency.

Giant electrical conductivity difference enabled liquid metal-hydrogel hybrid printed circuits for soft bioelectronics

Soft printed circuits is a vital component in electronic devices, which is designed to connect electrical components to exert certain functions. However, the design and fabrication of soft printed circuits still suffer from significant limitations including interconnection difficulties among varying materials with different stiffness, intrinsically low conductivity of typical soft materials like hydrogels, and the multi-material assembly and integration issues involved in the wiring and encapsulation process. Here we report a novel design paradigm of a soft printed circuit termed as liquid metal (LM)-hydrogel hybrid printed circuit (LMH-HPC), in which highly conductive LM functions as electrical wires while hydrogel can simultaneously work as the electrical junction, encapsulation, and bio-interfacing. The whole LMH-HPC maintains completely mechanically adapted (∼1–30 kPa) to soft tissues. Based on this LMH-HPC, we design soft hybrid circuits with movable but stable electrical connections with conventional solid electrical components. Owing to the giant electrical conductivity difference between LM and hydrogel, the current through the hydrogel can be tuned with density distribution at the hydrogel junction, which can be further utilized as the soft and safe bioelectronic interfaces for applications such as soft electrical stimulators for excitable cells and tissues, and iontophoresis-assisted wound dressing for antibacterial therapy. Overall, this LMH-HPC may set up a multifunctional platform for the design of hydrogel electronic devices.

The study of optical and electrical properties of AgInS2-based composite

sPhotovoltaic solar energy was one of the few sustainable and pollution-free energy sources. AgInS2 was a promising photovoltaic material, which had attracted considerable in long time due to its outstanding photovoltaic performance. Furthermore, the nanoparticles could improve the light absorption efficiency of absorption layer to enhance the photoelectric conversion efficiency of solar cell. In this paper, the suitable preparation methods of AgInS2 film and gold nanoparticles were used to improve the optical-electric performances of AgInS2-based solar cell. AgInS2 films were prepared by vacuum evaporation using different raw materials (Ag + In + S and Ag2S + In2S3) and then annealed at 400 °C or 425 °C. From absorption spectrum, the AgInS2 film, which was prepared by two components (Ag2S + In2S3) and annealed at 400 °C, had the highest absorption. And the transmission spectrum of the AgInS2 film was similar to that obtained from finite difference time domain simulation. Furthermore, this AgInS2 film was used to prepare AgInS2/CdS PN junction and AgInS2/gold/CdS PN junction. Due to the introduction of gold nanoparticles, the forward current of the AgInS2/gold/CdS PN junction increased an order of magnitude, but ideal factor and barrier height decreased, which meant that gold nanoparticles can promote carrier transport and improve electric property. As a result, this AgInS2/gold/CdS PN junction owned high absorption efficiency, low reverse saturation current and large barrier height, which meant huge application potential in solar cells field.

High‐Performance UV Photodetector via Energy Band Engineering and LSPR‐Enhanced Pyro‐Phototronic Effect in Au Decorated 2D‐PbI2/1D‐ZnO Heterojunction

AbstractUltraviolet (UV) photodetectors have attracted extensive attention in various applications, including aerospace, optical communication, and fire warning. However, the intrinsic coupling of high responsivity and fast response as well as imperfect interface transmission impede the further improvement of UV photodetector. Here, a high‐performance Au‐decorated PbI2/ZnO pn junction UV photodetector with a one‐dimensional (1D) and two‐dimensional (2D) interspersed structure is presented. The pyro‐phototronic effect and energy band engineering effect from the localized pn junction generated by the layered p‐type PbI2 nanosheets along the c‐axis of ZnO are coupled to modulate the separation and transport of photogenerated carriers. Furthermore, the localized surface plasmon resonance of Au nanoparticles produces transient thermal power to raise temperature fast to enhance pyroelectric current. The self‐powered Au@PbI2/ZnO photodetector displays a high responsivity of 0.21 A W−1, excellent detectivity of 7.9 × 1012 Jones, and fast response/recovery time of 25/31 ms, under the illumination of 325 nm light with the power density of 0.08 µW cm−2. This work offers an effective strategy for designing high‐performance next‐generation optoelectronic devices.

Research on discharge process of Bi2Te3 module under different thermal stimulation conditions

In the actual working process, the working environment temperature of the thermoelectric device is constantly changing, and rarely remains stable, a thermoelectric device is composed of more than one thermoelectric module monomer (PN junction), each of which can be used as an independent research object. To address this issue, the thermoelectric properties of thermoelectric modules (p, n-type Bi2Te3) are measured under different temperature environments. A self-constructed thermoelectric performance test platform, an infrared thermal imager, and a voltage acquisition system are used to monitor different temperature difference conditions in real-time. A transient discharge evaluation model was established to calculate the real-time discharge amplitude of the thermoelectric module based on its temperature gradient distribution. The results show that the error of the transient discharge evaluation model is about 5%, which is reliable. For large-sized thermoelectric modules, the maximum discharge amplitude under open circuit voltage can be obtained solely based on the overall temperature gradient of the thermoelectric module; the amplitude of the electrical output signals increases uniformly when the temperature difference between the two ends of the module is increasing uniformly; and the stable electrical output signals are also produced at both ends of the module when the temperature difference is stabilized. After stabilization, when the temperature drops uniformly, the amplitude of the electrical output signal decreases uniformly. In the range of T = 298–573 K, the greater the temperature difference between the two ends of the thermoelectric module is, the greater the amplitude of the stabilized electrical output signal is; and vice versa. The greater the rate of thermal loading, the faster the increase in the amplitude of the electrical output signal at both ends of the thermoelectric module. This also reduces the time needed to reach steady state equilibrium, enabling the thermoelectric module to produce a stable electrical output earlier than individual p and n-type Bi2Te3 modules.