Influence of GaInP ordering on the performance of GaInP solar cells

CuPt-type ordering with undesirable properties always occurs in GaInP at growth conditions that are very close to those leading to the highest quality material in metal organic chemical vapor deposition. In this work, highly disordered GaInP with high crystalline quality was obtained by optimizing growth conditions. Room-temperature and low-temperature photoluminescence (PL) spectra of AlGaInP/GaInP/AlGaInP double heterostructures (DHs) reveal that the band edge emission intensity is enhanced by optimizing growth temperature, V/III ratio, and reactor pressure at the expense of low energy peak originating from spatially indirect recombination due to the ordering-related defects. The DH sample with less ordering-related defects demonstrates a longer effective minority carrier lifetime, consequently, the GaInP solar cell shows a significant improvement in the performance.     

Computer simulation of an operation of the GaInP/AlGaInP QW VCSELs: Excitation of various transverse LPij modes

A comprehensive fully self-consistent optical–electrical–thermal-recombination model of the 650-nm oxide-confined GaAs-based GaInP/AlGaInP vertical-cavity surface-emitting diode lasers (VCSELs) is used to determine their anticipated room-temperature (RT) continuous-wave (CW) performance characteristics. As expected, for the devices with very large active regions, higher-order transverse LP_ij modes exhibit the lowest lasing thresholds. However, the desired single fundamental LP₀₁ mode operation remains dominating one for relatively large active regions of diameters up to as much as 10 mm. Therefore, the 650-nm GaInP/AlGaInP QW VCSELs have been found to offer a very promising RT CW performance as sources of carrier radiation for the optical communication taking advantage of plastic (polymer) optical fibers (POFs).     

应用于下一代太阳电池的2.05 eV AlGaInP 子电池研究

研制了应用于下一代高效多结太阳电池中的定电池的 Al0.13GaInP子电池,其实验室效率为10.04%,开路电压为1457.3mV,短路电流为11.9mA。使用量子效率来验证MOVPE生长过程中涉及高Al组分引起的O缺陷对电池性能的影响。相比GaInP单结电池,Al0.13GaInP电池的短路电流下降地较为厉害,实验中生长了GaInP/Al0.13GaInP异质结电池来分析其原因,因此也提出了以牺牲部分开路电压来提升短路电流的一种有效提升电池性能的方法。     

Analysis of perimeter recombination in the subcells of GaInP/GaAs/Ge triple‐junction solar cells

This paper studies the recombination at the perimeter in the subcells that constitute a GaInP/GaAs/Ge lattice‐matched triple‐junction solar cell. For that, diodes of different sizes and consequently different perimeter/area ratios have been manufactured in single‐junction solar cells resembling the subcells in a triple‐junction solar cell. It has been found that neither in GaInP nor in Ge solar cells the recombination at the perimeter is significant in devices as small as 500 μm × 500μm(2.5 ⋅ 10 ^{− 3} cm²) in GaInP and 250μm × 250μm (6.25 ⋅ 10 ^{− 4}cm²) in Ge. However, in GaAs, the recombination at the perimeter is not negligible at low voltages even in devices as large as 1cm², and it is the main limiting recombination factor in the open circuit voltage even at high concentrations in solar cells of 250 μm × 250μm (6.25 ⋅ 10 ^{− 4} cm²) or smaller. Therefore, the recombination at the perimeter in GaAs should be taken into account when optimizing triple‐junction solar cells. Copyright © 2014 John Wiley & Sons, Ltd.     

分子束外延生长的GaAs/GaInP双结电池研究

We report the recent result of GaAs/GaInP dual-junction solar cells grown by all solid-state molecularbeamepitaxy(MBE).The device structure consists of a GaIn0.48P homojunction grown epitaxially upon a GaAs homojunction,with an interconnected GaAs tunnel junction.A photovoltaic conversion efficiency of 27% under the AM1.5 globe light intensity is realized for a GaAs/GaInP dual-junction solar cell,while the efficiencies of 26% and 16.6% are reached for a GaAs bottom cell and a GaInP top cell,respectively.The energy loss mechanism of our GaAs/GaInP tandem dual-junction solar cells is discussed.It is demonstrated that the MBE-grown phosphide-containing Ⅲ–V compound semiconductor solar cell is very promising for achieving high energy conversion efficiency.     

Characteristics of bifacial solar cells under bifacial illumination with various intensity levels

The characteristics of bifacial solar cells with different rear structures were investigated under front, rear and bifacial illumination with an intensity of 0.4–4.2 suns. Five kinds of solar cells, rear flat local‐BSF cells, rear textured local‐BSF cells (textured RLB cells), rear total‐BSF cells, rear floating‐emitter cells, and triode cells with double‐sided junctions, were tested. The I–V characteristics of the cells under bifacial illumination were measured with a newly designed measurement system that simultaneously illuminated both surfaces of the cells. In the short‐circuit current (J_SC) and the saturation current evaluations, the bifacial illumination effect, which means that the power output of the cell is intrinsically improved by adding rear illumination, was not observed. Although the RLB cells showed a nonlinear increase in J_SC and enhanced V_OC, these increases did not make a practical contribution to extra output because of the low levels of these characteristics. When we evaluated the maximum output power, the bifacial illumination effect was only observed in the triode cell. A triode cell can decrease resistive loss by introducing light from both surfaces, compared with a conventional cell with one junction. Copyright © 2001 John Wiley & Sons, Ltd.     

高效硅基异质结太阳能电池的模拟

a-Si:H/c-Si异质结太阳能电池的基本参数,如层厚度、掺杂浓度、a-Si:H/c-Si界面缺陷、功函数等是影响载流子传输特性和电池效率的关键因素。在本文中,利用AFORS-HET程序,研究了这些参数与a-Si:H/c-Si电池的性能的关联性。最后,具有TCO/n-a-Si:H/i-a-Si:H/p-c-Si/p -a-Si:H/Ag结构的太阳能电池的最优化性能被获得,其光电转换效率为27.07%（VOC: 749 mV, JSC: 42.86 mA/cm2, FF: 84.33%）。深入地了解异质结电池的输运特性,对进一步提高电池的效率有很大的帮助,同时对实际太阳能电池的制造也能提供有益的指导。     

Properties of interfaces in GaInP solar cells

The effect of the properties of interfaces with Group-III phosphides on characteristics of GaInP solar cells has been studied. It is shown that the large valence band offset at the p-GaAs/p-AlInP interface imposes fundamental limitations on the use of p-AlInP layers as a wide-band-gap window in p-n structures of solar cells operating at ratios of high solar light concentration. It is demonstrated that characteristics of p-n solar cells can be, in principle, improved by using a double-layer wide-band-gap window constituted by p-Al_0.8Ga_0.2As and p-(Al_0.6Ga_0.4)_0.51In_0.49P layers.     

High-efficiency dual-junction GaInP/GaAs tandem solar cells obtained by the method of MOCVD

Monolithic dual-junction GaInP/GaAs solar cells grown by the MOCVD method were studied. The conditions of the growth of ternary Ga _x In_1?x P and Al _x In_1?x P alloys lattice-matched to GaAs are optimized. Technology for fabrication of a tunneling diode with a high peak current density of 207 A/cm² on the basis of heavily doped n ⁺⁺-GaAs:Si and p ⁺⁺-AlGaAs:C layers is developed. Cascade GaInP/GaAs solar cells obtained as a result of relevant studies featuring a good efficiency of the solar-energy conversion both for space and terrestrial applications. The maximum value of the GaInP/GaAs solar-cell efficiency was 30.03% (at AM1.5D, 40 suns).     

图形衬底对InGaN/GaN多量子阱太阳能电池性能的提升

In this paper, the enhanced performance of InGaN/GaN multiple quantum well solar cells grown on patterned sapphire substrates （PSS） was demonstrated. The short-circuit current （Jsc） density of the solar cell grown on PSS showed an improvement of 60%, compared to that of solar cells grown on conventional sapphire substrate. The improved performance is primarily due to the reduction of edge dislocations and the increased light absorption path by the scattering from the textured surface of the PSS. It shows that the patterned sapphire technology can effectively alleviate the problem of high-density dislocations and low Jsc caused by thinner absorption layers of the InGaN based solar cell, and it is promising to improve the efficiency of the solar cell.     

Analysis of Ge junctions for GaInP/GaAs/Ge three‐junction solar cells†

We study Ge solar cells with epitaxial GaInP windows for application as the third junction of GaInP/GaAs/Ge three‐junction solar cells. We demonstrate Ge junctions with open‐circuit voltages above 230 mV, fill factors above 65%, and internal quantum efficiencies of ∼90%. By varying separately the base and emitter contributions to the junction dark current, we deduce the factors limiting the performance of this device, and we project the improvement to the device performance that may be obtainable if key limiting factors such as the emitter surface‐recombination velocity can be mitigated. Published in 2001 by John Wiley & Sons, Ltd.     

GaInAsP/GaInP/AlGaInP MOCVD-grown diode lasers emitting at 808 nm

The MOCVD epitaxy has been used to grow the GaInAsP/GaInP/AlGaInP laser heterostructures with a narrow symmetric waveguide and broad asymmetric waveguide. Mesa stripe 100 μm aperture diode lasers emitting at 808 nm were manufactured. It is shown that a SiO₂/Si dielectric mirror coating of Fabry-Perot faces of Al-free semiconductor lasers does not result in catastrophic optical mirror damage. It is found that the maximum optical output power of Al-free diode lasers is limited by catastrophic optical damage of the laser heterostructure. Maximum values of optical output power of 5.1 and 9.9 W have been attained in diode lasers with a narrow symmetric waveguide and broad asymmetric waveguide, respectively.

     

Influence of wafer thickness on the performance of multicrystalline Si solar cells: an experimental study

The influence of the thickness of silicon solar cells has been investigated using neighbouring multicrystalline silicon wafers with thickness ranging from 150 to 325 μm. For silicon solar cell structures with a high minority‐carrier diffusion length one expects that J_sc would decrease as the wafer becomes thinner due to a shorter optical path length. It was found experimentally that J_sc is nearly independent of the thickness of the solar cell, even when the minority‐carrier diffusion length is about 300 μm. This indicates that the Al rear metallisation acts as a good back surface reflector. A decrease in J_sc is observed only if the wafer thickness becomes less than about 200 μm. The observed trend in V_oc as a function of the wafer thickness has been explained with PC1D modelling by a minority‐carrier diffusion length in the Al‐oped BSF which is small in relation to the thickness of the BSF. This effectively increases the recombination velocity at the rear of the cell. We have shown that the efficiency of solar cells made with standard industrial processing is hardly reduced by reducing the wafer thickness. Solar cell efficiencies might be increased by better rear surface passivation. Copyright © 2002 John Wiley & Sons, Ltd.     

Understanding of the annealing temperature impact on ion implanted bifacial n‐type solar cells to reach 20.3% efficiency

Ion implantation has the advantage of being a unidirectional doping technique. Unlike gaseous diffusion, this characteristic highlights strong possibilities to simplify solar cell process flows. The use of ion implantation doping for n‐type PERT bifacial solar cells is a promising process, but mainly if it goes with a unique co‐annealing step to activate both dopants and to grow a SiO₂ passivation layer. To develop this process and our SONIA cells, we studied the impact of the annealing temperature and that of the passivation layers on the electrical quality of the implanted B‐emitter and P‐BSF. A high annealing temperature (above 1000 °C) was necessary to fully activate the boron atoms and to anneal the implantation damages. Low J_0BSF (BSF contribution to the saturation current density) of 180 fA/cm² was reached at this high temperature with the best SiO₂ passivation layer. An average efficiency of 19.7% was reached using this simplified process flow (“co‐anneal process”) on large area (239 cm²) Cz solar cells. The efficiency was limited by a low FF, probably due to contaminations by metallization pastes. Improved performances were achieved in the case of a “separated anneals” process where the P‐BSF is activated at a lower temperature range. An average efficiency of 20.2% was obtained in this case, with a 20.3% certified cell. Copyright © 2014 John Wiley & Sons, Ltd.     

Multijunction GaInP/GaInAs/Ge solar cells with Bragg reflectors

Effect of subcell parameters on the efficiency of GaInP/Ga(In)As/Ge tandem solar cells irradiated with 1-MeV electrons at fluences of up to 3 × 10¹⁵ cm⁻² has been theoretically studied. The optimal thicknesses of GaInP and GaInAs subcells, which provide the best photocurrent matching at various irradiation doses in solar cells with and without built-in Bragg reflectors, were determined. The dependences of the photoconverter efficiency on the fluence of 1-MeV electrons and on the time of residence in the geostationary orbit were calculated for structures optimized to the beginning and end of their service lives. It is shown that the optimization of the subcell heterostructures for a rated irradiation dose and the introduction of Bragg reflectors into the structure provide a 5% overall increase in efficiency for solar cells operating in the orbit compared with unoptimized cells having no Bragg reflector.     

垒层Si掺杂对AIGaInP/GaInP多量子阱性能的影响

低压MOCVD方法生长了垒层掺Si与不掺Si的AlGaInP/GaInP多量子阱结构,运用X双晶衍射与光荧光技术研究了掺Si对量子阱性能的影响.测试结果表明垒层掺Si使量子阱的生长速度增加,掺Si量子阱的光荧光强度比未掺Si量子阱的光荧光强度增强了1 3倍.     

Effect of the Ag Nanoparticle Concentration in TiO<Subscript>2</Subscript>–Ag Functional Coatings on the Characteristics of GaInP/GaAs/Ge Photoconverters

The results of studying the effect of the silver nanoparticle concentration in TiO₂–Ag functional coatings on the characteristics of GaInP/GaAs/Ge photoconverters are discussed. The optimum concentration of silver nanoparticles in TiO₂ coatings, improving the functional characteristics of solar cells is determined.     

Simulation analysis of the effects of a back surface field on a p-a-Si:H/n-c-Si/n+-a-Si:H heterojunction solar cell

In order to investigate the effects of a back surface field (BSF) on the performance of a p-doped amorphous silicon (p-a-Si:H)/n-doped crystalline silicon (n-c-Si) solar cell, a heterojunction solar cell with a p-a-Si:H/nc-Si/n+-a-Si:H structure was designed. An n+-a-Si:H film was deposited on the back of an n-c-Si wafer as the BSF.The photovoltaic performance of p-a-Si:H/n-c-Si/n+-a-Si:H solar cells were simulated. It was shown that the BSF of the p-a-Si:H/n-c-Si/n+-a-Si:H solar cells could effectively inhibit the decrease of the cell performance caused by interface states.     

Effect of Sb on the quantum efficiency of GaInP solar cells

The energy bandgap of GaInP solar cells can be tuned by modifying the degree of order of the alloy. In this study, we employed Sb to increase the energy bandgap of the GaInP and analyzed its impact on the performance of GaInP solar cells. An effective change in the cutoff wavelength of the external quantum efficiency of GaInP solar cells and an effective increase of 50 mV in the open‐circuit voltage of GaInP/Ga(In)As/Ge triple junction solar cells were obtained with the use of Sb. Copyright © 2016 John Wiley & Sons, Ltd.     

High-performance 670-nm AlGaInP/GaInP visible strained quantum welllasers

We have grown high-performance AlGaInP/GaInP visible (670 mn) strained quantum well lasers by low-pressure metalorganic chemical vapor deposition. With AlInP cladding layer, a high-power AlGaInP/GaInP visible laser diode is achieved. Its threshold current is about 30 mA. The output power of this laser diode can maintain, at least, at 32 mW under continuous-wave (CW) operation at room temperature. High slope efficiency (0.8 mW/mA) and differential quantum efficiency (0.87) can be achieved. To improve beam quality, AlGaInP/GaInP visible lasers with and without depressed index cladding layer are theoretically and experimentally studied. From experimental results, the transverse beam divergence can be reduced from 41.4° to 26.2° while maintaining a low threshold current (from 36 mA to 46 mA). By using the transfer matrix method, our theoretical calculations are in good agreement with the experimental results