Electron Diffusion Length Research Articles

Charge Carrier Collection Losses in Lead‐Halide Perovskite Solar Cells

AbstractThe collection of photogenerated charges in halide perovskite solar cells depends on the thickness of the absorber layer, with larger thicknesses leading to a reduced collection efficiency. This observation has traditionally been associated with insufficiently high electron and hole diffusion lengths in the absorber layers. However, it is shown that in the presence of low‐mobility contact layers, charge collection can be thickness‐dependent, even if the absorber layer has infinite mobility. Here, analytical equations are derived for the thickness dependence of charge collection losses in situations where recombination is bulk or interface‐limited and show how to relate these equations to voltage‐dependent photoluminescence data. The analytical equations are compared to experimental data and numerical simulations and it is observed that experimental data on triple‐cation perovskite devices with different thicknesses approximately follows the case, where bulk recombination dominates.

Electron Diffusion Length Effect on Direction of Irradiance in Transparent FAPbBr3 Perovskite Solar Cells.

Transparent photovoltaics for building integration represent a promising approach for renewable energy deployment. These devices require transparent electrodes to manage transmittance and to ensure proper cell operation. In this study, transparent FAPbBr3-based perovskite solar cells optimized via a passivation treatment were demonstrated with average visible transmittance values above 60% and light utilization efficiencies up to 5.0%. Experiments under varying ultraviolet (UV) irradiance intensities from both front and rear directions revealed performance differences correlated with diffusion-limited transport and open-circuit voltage changes. Combining the UV-radiated experiments and drift-diffusion simulations, an asymmetry between the diffusion lengths of electrons and holes in the perovskite is revealed, with estimated values resulting in less than 50 nm and more than 99 nm, respectively. Our methods not only identify electron-hole diffusion length differences but also introduce a general protocol for characterizing solar cells with transparent electrodes.

Management of Light Absorption Based on Sidewall Reflection for Fabricating High-Performance Flexible Nano-Coned Sb2Se3 Thin Film Photovoltaics.

High performance and robustness are the key factors to boosting wearable and portable applications. Although the 1D crystal structure makes the Sb2Se3 thin film more tolerant to physical deformation upon bending, the conventional planar structures still cannot undergo repeated mechanical bending due to the induced stress/strain inside devices, which can be well addressed by constructing three-dimensional nanostructures. Besides, the electron diffusion length has two values, 0.3 μm in the [221] direction and 1.7 μm in the [001] direction, in the Sb2Se3 thin film, which limits the absorber thickness, for getting an effective carrier collection; thus, a strong light trapping effect enabling sufficient light harvesting is needed to allow the use of a very thin light absorption layer. Herein, the nanoconed Sb2Se3 solar cells have been designed, and their light absorption behaviors were investigated within a finite-element simulation under the substrate back-reflection, indicating that the reflection of the bottom part always works positively, while the effect of the nanocone sidewall on absorption enhancement largely depends on its geometry, arising from resonant or scattering modes. These results provide a practical guide in designing/establishing an easier/simpler way to fabricate high-performance and mechanically stable flexible nanostructured Sb2Se3 thin film solar cells.

Approaching 20% Efficiency in Ortho-Xylene Processed Organic Solar Cells by a Benzo[a]phenazine-Core-Based 3D Network Acceptor with Large Electronic Coupling and Long Exciton Diffusion Length.

High-performance organic solar cells often rely on halogen-containing solvents, which restrict the photovoltaic industry. Therefore, it is imperative to develop efficient organic photovoltaic materials compatible with halogen-free solvents. Herein, a series of benzo[a]phenazine (BP)-core-based small-molecule acceptors (SMAs) achieved through an isomerization chlorination strategy is presented, comprising unchlorinated NA1, 10-chlorine substituted NA2, 8-chlorine substituted NA3, and 7-chlorine substituted NA4. Theoretical simulations highlight NA3's superior orbit overlap length and tight molecular packing, attributed to interactions between the end group and BP unit. Furthermore, NA3 demonstrates dense 3D network structures and a record electronic coupling of 104.5 meV. These characteristics empower the ortho-xylene (o-XY) processed PM6:NA3 device with superior power conversion efficiency (PCE) of 18.94%, surpassing PM6:NA1 (15.34%), PM6:NA2 (7.18%), and PM6:NA4 (16.02%). Notably, the significantly lower PCE in the PM6:NA2 device is attributed to excessive self-aggregation characteristics of NA2 in o-XY. Importantly, the incorporation of D18-Cl into the PM6:NA3 binary blend enhances crystallographic ordering and increases the exciton diffusion length of the donor phase, resulting in a ternary device efficiency of 19.75% (certified as 19.39%). These findings underscore the significance of incorporating new electron-deficient units in the design of efficient SMAs tailored for environmentally benign solvent processing of OSCs.

Improving the efficiency and stability of betavoltaic batteries based on understanding efficiency fluctuations and gaps with theoretical limits

Wide-bandgap semiconductors are regarded as preferred materials for preparing semiconductor conversion devices in betavoltaic batteries due to their high theoretical conversion efficiency (ηc). However, there are a few comprehensive analytical studies on why the experimental values of ηc are generally much lower than the theoretical limit of ηc (ηc-limit) and how to improve ηc and its stability. In this work, combined with the energy deposition distributions of Ti3H2, 63Ni, and 147Pm2O3 radioactive sources in SiC obtained from Monte Carlo simulations, a multi-physical mechanism, multi-parameter coupling numerical model was established. This model can comprehensively analyze the output characteristics of betavoltaic batteries under the influence of actual device structural and material parameter changes. Our results show that changes in structural and material parameters cause significant variations in the collection efficiency (Q) of the radiation-generated electron–hole pair (RG-EHP). Considering structural parameters are easy to control, instabilities in actual SiC material parameters, which include electron diffusion length (Ln), hole diffusion length (Lp), and surface recombination velocity (S), are the main reason that ηc fluctuates significantly and is generally far lower than ηc-limit. Due to differences in the distribution of RG-EHP produced by different radioactive sources in SiC, the dominant parameters causing ηc fluctuations differ. By analyzing differences in recombination loss mechanisms under different radioactive sources, the device structures were designed in a targeted manner to make ηc closer to ηc-limit. Meanwhile, when the SiC material quality fluctuates, the stability of ηc increases by 58.5%, 35.3%, and 48.2% under Ti3H2, 63Ni, and 147Pm2O3, respectively.

Long‐Range Charge Carrier Transport in Planar Polymer Bulk‐Heterojunction Photovoltaic Cells

One‐dimensional scanning optical beam‐induced current (OBIC) measurements have been carried out on polymer bulk heterojunction (BHJ) photovoltaic cells with a planar, or lateral configuration. The planar P3HT:PCBM cells have parallel aluminum or gold electrodes that are 390 to 560 micrometers apart. When a focused laser beam is scanned across the electrode gap, photocurrent or photovoltage is recorded as a function of beam position along with the transmission of the excitation beam. Despite the large electrode gap size, cells with symmetric Al/Al electrodes exhibit significant photocurrent and photovoltage which are the highest at the electrode interfaces and null at the cell center. The OBIC in these large planar polymer BHJ cells is attributed to the metal/BHJ blend Schottky junction. The larger Schottky barrier of the Al/BHJ junction gives rise to a stronger OBIC response than the Au/BHJ junction. The photocurrent and photovoltage always have opposite signs and are antisymmetric about the cell center. In asymmetric Al/Au cells, the electrode work function difference contributes an additional built‐in field/potential drop and significantly modifies the photocurrent and photovoltage profiles. The depletion width of the Al/BHJ Schottky junction is 110–120 μm, while the minority electron diffusion length is determined to be 43.8 μm.

Competition between Transport and Recombination in Dye Solar Cells at Low Light Intensity

The efficiency of electron collection in a dye‐sensitized solar cell (DSC) is determined by a delicate balance between electronic transport and recombination losses caused by electron transfer to dye cations and electron acceptors. While state‐of‐the‐art DSCs have demonstrated quantitative electron collection under standard 1 sun conditions, the nonlinear nature of the trapping/detrapping dynamics in the photoanode with respect to the stored electronic charge can result in suboptimal performance under the low illumination intensity conditions commonly found indoors. Herein, the key factors influencing electron collection in relation to light intensity using impedance spectroscopy and numerical analysis are thoroughly examined. Impedance analysis reveals that the electron diffusion length tends to decrease as the quasi‐Fermi level is lowered, approaching the critical limit (Ln/d ≈ 1) at intensities characteristic of indoor illumination. A range of tert‐butyl pyridine concentrations and different thermal and chemical treatments of the TiO2 are tested, showing that this low intensity limitation is inherent to the multiple‐trapping mechanism that governs the functioning of a DSC. It is concluded that relatively high ideality factors, nonoptimal electrolyte compositions, or small variations in the quality of the TiO2 layer can result in electron collection limitations that are not apparent under 1 sun but become noticeable at low light intensities.

Unravelling the Photoelectrochemical Water Splitting of Nanometer-Thick Carbon Nitride Layer.

Matching the thickness of the graphitic carbon nitride (CN) nanolayer with the charge diffusion length is expected to compensate for the poor intrinsic conductivity and charge recombination in CN for photoelectrochemical cells (PEC). Herein, the compact CN nanolayer with tunable thickness is in situ coated on carbon fibers. The compact packing along with good contact with the substrate improves the electron transport and alleviates the charge recombination. The PEC investigation shows CN nanolayer of 93nm-thick yields an optimum photocurrent of 116µAcm-2 at 1.23V versus RHE, comparable to most micrometer-thick CN layers, with a low onset potential of 0.2V in 1m KOH under 1 sun illumination. This optimum performance suggests the electron diffusion length matches with the thickness of the CN nanolayer. Further deposition of NiFe-layered double hydroxide enhanced the surface water oxidation kinetics, delivering an improved photocurrent of 210µAcm-2 with IPCE of 12.8% at 400nm. The CN nanolayer also shows extended potential in PEC organic synthesis. This work experimentally reveals the PEC behavior of the nanometer-thick CN layer, providing new insights into CN in the application of energy and environment-related fields.

Promoting effect of lanthanum doping on photovoltaic performance of CZTSSe solar cells.

A large open-circuit voltage (VOC) deficit is the major challenge hindering the efficiency improvement of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Cation substitution, or doping, is usually an effective strategy to achieve carrier regulation and improve efficiency. In this work, we developed a rare-earth element lanthanum (La) doped CZTSSe thin-film solar cell by directly introducing La3+ ions into the CZTS precursor solution. Such a proposed La doping approach could effectively enhance light harvesting, adjust the bandgap, and increase the electron diffusion length. Furthermore, appropriate concentrations of La doping can reduce harmful defect cluster. Benefiting from the La doping, the VOC significantly increases from 431 to 497 mV. Consequently, the power conversion efficiency is enhanced significantly from 6.54% (VOC = 431 mV, JSC = 25.50 mA/cm2, FF = 58.28%) for the reference cell to 10.21% (VOC = 497 mV, JSC = 35.20 mA/cm2, FF = 58.41%) for the optimized La-doped cell. This research provides a new direction for enhancing the performance of CZTSSe cells, offering promising prospects for the future of CZTSSe thin-film solar cells.

Ideal Structures of Isolated BiVO4 Nanoparticles on WO3 Nanocorals to Enhance Photoelectrochemical Hydrogen Evolution

Metal oxide nanoparticles (NPs) of n-type semiconductors have recently garnered significant attention in the photoelectrochemical (PEC) field. In this study, isolated BiVO4 NPs on anodized WO3 nanocorals are investigated with respect to the formation mechanism of the NPs and the correlation between particle size and PEC efficiency. The sizes and distances of the BiVO4 NPs on the WO3 nanocorals are controlled via spin-coating and heat-treatment. The optimized BiVO4 NPs, with ideal sizes of 10 nm and distances of 100 nm between them, exhibit satisfactory electron and hole diffusion lengths, suppressing electron–hole recombination and promoting the exposure of WO3 to ultraviolet light. Furthermore, high-quality BiVO4, without the formation of by-products due to the optimized concentrations of Bi and V in the precursor solution, results in a 2.3-fold higher photocurrent density and H2 production, and a 6-fold higher incident photon-to-current conversion efficiency (IPCE) compared to those of pristine WO3 nanocorals.

Electrochemical impedance spectroscopy analysis of dye-sensitized solar cells composed of electrospun composite photoanodes: A comparative study of natural and synthetic sensitizers

In this study, a transmission line model is applied to the electrochemical impedance spectroscopy (EIS) data of the fabricated dye-sensitized solar cells (DSSCs) to evaluate the charge transfer mechanism through the cells. Natural dye from black plum (Syzygium cumini) fruit was used as a cell sensitizer (SC-DSSC) and compared its photovoltaic and electron transport capabilities to those of a cell using a synthetic sensitizer (N719-DSSC). TiO2/ZnO electrospun composite nanofibers were used as the semiconductor layer of the photoanode to enhance electron transfer. The EIS analysis revealed the role of electron resistances through shant, interfaces, and electrolyte solution by measuring the electron transfer kinetic parameters of each element. Based on the results, the SC-DSSC and N719-DSSC are appropriate photovoltaic cells because their ratios of effective electron diffusion length to photoanode thickness are 12.5 and 2.8, respectively. The EIS analysis showed that the electrospun composite nanofiber coated on the photoanode reduces the semiconductor layer's electrical resistance to the cell's total resistance. The extracted natural dye also boosted electron lifetime to 3.68 ms and diffusion coefficient to 54.3×10−6 m2/s while minimizing back-electron recombination at the semiconductor-electrolyte interface. Moreover, the semiconductor-electrolyte interface resistance is over 85% of the overall resistance for both DSSCs and controls electron transport through the cells, which is due to the dye-semiconductor binding intensity. Based on the photovoltaic data, the SC-DSSC cell efficiency was lower than N719-DSSC which is attributed to its higher electron transfer rate-controlling element. Thus, enhancing dye-semiconductor interactions will decrease the rate-controlling impedance and enhance cell performance.

Regulation of Hot Electrons Transport Achieved through Controlled Electron-Phonon Coupling in Metallic Heterostructures.

The electron-phonon (e-ph) interactions are pivotal in shaping the electrical and thermal properties, and in particular, determining the carrier dynamics and transport behaviors in optoelectronic devices. By employing pump-probe spectroscopy and ultrafast microscopy, the consequential role of e-ph coupling strength in the spatiotemporal evolution of hot electrons is elucidated. Thermal transport across the metallic interface is controlled to regulate effective e-ph coupling factor Geff in Au and Au/Cr heterostructure, and their impact on nonequilibrium transport of hot electrons is examined. Via the modulation of buried Cr thickness, a strong correlation between Geff and the diffusive behavior of hot electrons is found. By enhancing Geff through the regulation of thermal transport across interface, there is a significant reduction in e-ph thermalization time, the maximum diffusion length of hot electrons, and lattice heated area which are extracted from the spatiotemporal evolution profiles. Therefore, the increased Geff significantly weakens the diffusion of hot electrons and promotes heat relaxation of electron subsystems in both time and space. These insights propose a robust framework for spatiotemporal investigations of G impact on hot electron diffusion, underscoring its significance in the rational design of advanced optoelectronic devices with high efficiency.

Ceiling of Barium Substitution for B-Site Cation in Organometal Halide Perovskite Solar Cells

Significant advancements have been made in the development of perovskite solar cells (PSCs) in recent years, resulting in increased efficiency rates. Nonetheless, the presence of lead within these cells has become a pressing concern. Our study investigates the correlation between tolerance of barium substitution and A-site cation composition through systematic analysis of morphology, crystal structure, optical property, and carrier dynamics. The results show that a high barium substitution ratio of 15 mol.% can be achieved by inducing 60 mol.% of a large A-site cation, formamidinium, into the methylammonium-based perovskite. The induction of large A-site cations in barium-substituted perovskite overcomes the imbalance between hole and electron diffusion lengths, resulting in an electron and a hole diffusion length of 395 nm and 440 nm, respectively. The champion device for 15 mol.% barium-substituted perovskite, FA0.6MA0.4Pb0.85Ba0.15I3-yCly, achieves a PCE of 11.13%, which is the highest record for 15 mol.% of lead reduction. This study provides insights into the limitations of lead substitution in perovskite solar cells and highlights the ceiling for barium substitution ratio in mixed cation perovskite.

Improvement and structure optimization of transmission-mode GaAs photocathode performance

In order to improve the performance of transmitted GaAs photoelectric cathode, the quantum efficiency curve of Chinese transmitted GaAs photoelectric cathode is compared with that of the product of American ITT company, showing that the integration sensitivity of Chinese transmitted photoelectric cathode is 2130 μA/lm, and the American ITT company’s reaches 2330 μA/lm. Through the matrix method to solve the three membranes, the theoretical reflectivity is obtained. Based on the uniform doping transmission GaAs photocathode quantum efficiency formula, by replacing the fixed value <i>R</i> with variable value <inline-formula><tex-math id="M1">\begin{document}$ {R}_{{\mathrm{t}}{\mathrm{h}}{\mathrm{e}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20231542_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20231542_M1.png"/></alternatives></inline-formula>, adding the short wave constraint factor, and modifying the quantum efficiency formula, a modified uniform doping transmission GaAs photocathode quantum efficiency formula is obtained. Using the revised quantum efficiency, optical performance and integral sensitivity theory model, through fitting the quantum efficiency curve of American ITT company product , introducing the ITT cathode component performance parameters, comparing the performance parameters of Chinese product, the results show that the Chinese photocathode in the window layer, the thickness of the emission layer, electron diffusion length and rear interface composite rate has a certain gap with ITT’s. In order to shorten the gap between the two and optimize the cathode structure parameters, the transmission GaAs photocathode optical structure software is designed to further analyze the influence of the electron diffusion length and the emission layer thickness on the quantum efficiency of the photocathode. The results show that with an electron diffusion length of 7 μm and emission layer thickness of 1.5 μm, the transmitted GaAs photocathode sensitivity can be more than 2800 μA/lm. However, the large electron diffusion length has high requirements for cathode materials and preparation level. The reasons responsible for the performance gap between Chinese product and other country’s are that in China the growth process of cathode materials is not jet matureand the cathode preparation equipment is out of date . In this paper, we study the relationship between GaAs photocathode optical performance and photoemission performance, and further optimize the structural design of cathode components, which has certain guiding significance for improving the cathode quantum efficiency and the level of image intensifier.

Efficient Blade-Coated p-i-n Perovskite Solar Cells and Modules Enabled by Effective Molecular N Doping.

N doping is an essential strategy to prolong electron diffusion length and improve the photovoltaic performance of p-i-n structured perovskite solar devices, but current n-dopants generally suffer from air instability, poor compatibility with perovskites, and the compensation from perovskite intrinsic defects, thus limiting their doping effectiveness. To address these issues, in this work, a new perovskite n-doping strategy is developed by incorporating an air-stable n-dopant (1-ethyl-3-methylimidazolium-2-carboxylate, EMIC) that has no detrimental effects on perovskite crystallinity and morphology. EMIC is soluble in most polar solvents and can be readily introduced into perovskite precursor solutions. Upon thermal annealing of perovskite films, the decarboxylation of EMIC releases imidazolylidene, a reactive species that highly tends to donate electrons and thus efficiently prolongs the electron diffusion length from 0.57µm to over 1.21µm. As a result, the blade-coated perovskite solar cells and modules realize high power conversion efficiencies of 24.3% and 20.6% at 7.4mm2 and 25.0cm2 aperture areas, respectively.

Temperature‐Dependent Interplay between Structural and Charge Carrier Dynamics in CsMAFA‐Based Perovskites

AbstractState‐of‐the‐art triple cation, mixed halide perovskites are extensively studied in perovskite solar cells, showing very promising performance and stability. However, an in‐depth fundamental understanding of how the phase behavior in Cs0.05FA0.85MA0.10Pb(I0.97Br0.03)3 (CsMAFA) affects the optoelectronic properties is still lacking. The refined unit cell parameters a and c in combination with the thermal expansion coefficients derived from X‐ray diffraction patterns reveal that CsMAFA undergoes an α–β phase transition at ≈280 K and another transition to the γ‐phase at ≈180 K. From the analyses of the electrodeless microwave photoconductivity measurements it is shown that shallow traps only in the γ‐phase negatively affect the charge carrier dynamics. Most importantly, CsMAFA exhibits the lowest amount of microstrain in the β‐phase at around 240 K, corresponding to the lowest amount of trap density, which translates into the longest charge carrier diffusion length for electrons and holes. Below 200 K a considerable increase in deep trap states is found most likely related to the temperature‐induced compressive microstrain leading to a huge imbalance in charge carrier diffusion lengths between electrons and holes. This work provides valuable insight into how temperature‐dependent changes in structure affect the charge carrier dynamics in FA‐rich perovskites.

Efficiently catalyzing photo-oxidation of water by surface engineering of bismuth vanadate with nickel molybdenum oxide coverages

Bismuth vanadate with suitable band edges is one of the efficient photocatalysts for water oxidation. Establishing heterojunction can improve electron diffusion lengths and photocatalytic ability of BiVO4. In this work, nickel molybdenum oxide (Ni–Mo–O) and BiVO4 heterojunction is established by the hydrothermal process with different nickel to molybdenum precursor ratios. The Ni–Mo–O/BiVO4 electrode is applied as photoanodes for water oxidation. The growth mechanism of Ni–Mo–O on BiVO4 surface is proposed. The Ni–Mo–O deposition amount is optimized regarding to light absorbance and charger transportation. The largest photocurrent density of 1.72 mA/cm2 at 1.23 VRHE is obtained for the optimal NiMoO4/BiVO4 electrode (NM12) in the electrolyte without hole scavenger, while the pure BiVO4 electrode only shows a photocurrent density of 0.90 mA/cm2. The NM12 electrode even presented an impressive photocurrent density of 5.39 mA/cm2 at 1.23 VRHE in the electrolyte with the hole scavenger, owing to the abundant active sites and higher light absorbance as well as the favorable synergistic effects from its suitable Ni to Mo ratio. The NM12 electrode also shows excellent long-term stability with the photocurrent retention of 83% after illumination for 6500 s. This work opens a blueprint for establishing a novel heterojunction with the adjustable metal ratio and coverage on BiVO4.

Investigation on short–circuit current density (Jsc) in the dye-sensitized solar cells by optimizing photoelectrode thickness

The photoelectrode of dye-sensitized solar cells (DSSC) is a vital part that loads the dye, transports the generated photoelectrons to the external load, and serves as an interface between the current collector and the dye. The performance of the DSSCs is highly influenced by the thickness of the photoelectrode. The short-circuit current density (Jsc) of the DSSC increases with thickness and reaches its maximum at a particular thickness, after which Jsc decreases and saturates. A theoretical approach is formulated, using which the optimal thickness required to obtain maximum Jsc for the DSSC is calculated. A novel analytical expression for optimal diffusion length (L0), which is the electron diffusion length required to maximize Jsc is derived. The experimental validation of the simulated results is carried out with DSSCs of varying photoelectrode thickness. These validation results suggest that this theoretical approach to determine the optimal thickness of photoelectrodes enhances the efficiency of dye-sensitized solar cells.

Enhancements on oxygen vacancy and light absorption of alkaline-etched BiVO4 for photoelectrochemical water oxidation

Designing the favorable morphology with large surface area and abundant oxygen vacancies for BiVO4 can enhance its electron diffusion lengths and improve its photocatalytic ability toward photoelectrochemical water oxidation. The ex-situ alkaline etching process is reported to be facile for enhancing the light absorption and oxygen vacancy of BiVO4, but the systematic study of alkaline etching on the photocatalytic ability of BiVO4 is rare. In this study, alkaline-etched BiVO4 is firstly fabricated using a hydrothermal process with different durations as the photocatalyst of water oxidation. The BiVO4 etched by alkaline for longer durations presents rougher surface, more oxygen vacancies and higher light absorption. The larger carrier densities and the smaller charge-transfer resistances are also achieved for the alkaline etched BiVO4. The largest photocurrent density of 2.38 mA/cm2 is achieved at 1.23 V versus reversible hydrogen electrode in the Na2SO4 electrolyte for BiVO4 etched by alkaline for 45 min, while the pristine BiVO4 electrode only shows a photocurrent density of 0.59 mA/cm2. The photocurrent retention of 81% is also obtained for the alkaline etched BiVO4 electrode after continuous illumination for 6000 s. The results imply the feasibility of applying the alkaline etching process on refining the photoelectrochemical catalytic ability of BiVO4.

Measurement of minority carrier diffusion length in p-GaN using electron emission spectroscopy (EES)

Electron emission spectroscopy was performed on metalorganic chemical vapor deposition grown p-n−-n+ junctions with p-thicknesses ranging from 50 to 300 nm, doped with [Mg] = 3.5 × 1019 cm−3. By measuring the decreasing emitted electron intensity from a cesiated p-GaN surface with increasing p-thickness, we were able to extract the minority carrier diffusion length of electron in p-type GaN, Le = 26 ± 3 nm. The measured value is in good agreement with literature reported values. The extrapolated electron current at the n− region–p-GaN interface is in reasonable agreement with the simulated electron current at the interface.