Role of dual SiOx: H based buffer at the p/i interface on the performance of single junction microcrystalline solar cells

In p-i-n structure a-Si solar cell a buffer layer with proper characteristics plays important role in improving the p/i interface of the cell, reducing mismatch of band gaps and number of recombination centres. However for p-i-n structure microcrystalline ( µc-Si: H) cell which has much less light induced degradation than a-Si:H cell, not much work has been done on development of proper buffer layer and its application to µc-Si:H cell. In this paper we have reported the development of two intrinsic oxide based microcrystalline layer having different characteristics for use as buffer layers at the p/i interface of µc-Si:H cell. Previously SiO_x:H buffer layer has been used at the p/i interface which showed positive effects. To explore the possibility of improving the performance of p-i-n structure µc-Si:H cell further we have thought it interesting to use two buffer layers with different characteristics at the p/i interface. The two buffer layers have been characterized in detail and applied at the p/i interface of the µc-Si:H cell with positive effects on all the PV parameters mainly improves the open circuit voltage (V_oc) and enhances short circuit current (I_sc). The maximum initial efficiency obtained is 8.97% with dual buffer which is 6.7% higher than that obtained by using conventional single buffer layer at the p/i interface. Stabilized efficiency of the cell with dual buffer is found to be ~9.5% higher than that with single buffer after 600 h of light soakings.     

A study of the i/p interface for flexible n–i–p a-Si:H thin film solar cells

In this paper, the influence of i/p interface buffer layer on the performance of flexible n–i–p a-Si:H thin film solar cells is studied. The results show that the dopant distribution in the buffer layer has large effect on the property of solar cells. A larger open circuit voltage and fill factor can be obtained when methane is introduced into the chamber prior to diborane during the deposition of buffer layer. The AMPS simulation indicates that it is beneficial to improve the built-in electric field in the i layer when the carbon is doped prior to boron, thus the carrier transport properties are improved. By further optimizing the deposition parameter, an initial conversion efficiency of 5.668% is achieved for the a-Si:H thin film solar cells on the PI substrates at 150 °C.     

a-Si/c-Si异质结结构太阳能电池设计分析

通过应用 Scharfetter- Gum mel解法数值求解 Poisson方程 ,对热平衡态 a- Si/ c- Si异质结太阳能电池进行计算机数值模拟分析 ,着重阐述在 a- Si/ c- Si异质结太阳能电池中嵌入 i( a- Si:H)缓冲薄层的作用 ,指出采用嵌入 i( a- Si:H )缓冲薄层设计能有效增强光生载流子的传输与收集 ,从而提高 a- Si/ c- Si异质结太阳能电池的性能 ,同时还讨论 p+ ( a- Si:H)薄膜厚度和 p型掺杂浓度对光生载流子传输与收集的影响 ,而高强度光照射下模拟计算表明 ,a- Si/ c- Si异质结结构太阳能电池具有较高光稳定性     

异质结硅太阳能电池a—Si：H薄膜的研究

通过应用Scharfetter-Gummel数值求解Poisson方程，对热平衡态P^ （a-Si:H)/n(c-Si)异质结太阳能电池进行计算机数值模拟分析。结果指出，采用更薄P^ (a-Si：H）薄膜设计能有效增强光生载流子的传输与收集，从而提高a-Si/c-Si异质结太阳能电池的性能。同时，还讨论了P^ (a-Si:h)薄膜中P型掺杂浓度对光生载流了传输与收集的影响。高强茺光照射下模拟，计算表明，a-Si/c-Si异质结结构太阳能电池具有较高光稳定性。     

Optimization of a-Si:H absorber layer grown under a low pressure regime by plasma-enhanced chemical vapor deposition: Revisiting the significance of the p/i interface for solar cells

In this study, we revisited the significance of the p/i interface for hydrogenated amorphous silicon (a-Si:H) solar cells. Initially, intrinsic and extrinsic (p and n type) a-Si:H layers were grown in a low pressure regime (0.5–0.1 Torr) using the conventional RF plasma-enhanced chemical vapor deposition process and their opto-electronic properties were optimized for the fabrication of p–i–n a-Si:H solar cells. Subsequently, we obtained new insights in terms of the activation energy and band gap at the p/i interface in these solar cells. The absorber layers deposited at pressures of 0.23 Torr and 0.53 Torr had the highest photosensitivity with a band absorption edge at ~700 nm. Furthermore, the photosensitivity was shown to be correlated with the estimated diffusion length, which effectively defined the carrier transport within the solar cell layers. Moreover, the cell efficiency increased from 1.53% to 5.56% due to the improved p/i interface as well as the higher photosensitivity of the intrinsic/absorber layer.     

Pd/a-Si:H界面的光电子能谱研究

本文利用光电子能谱(XPS、UPS)技术研究了Pd淀积层与离子注入制备的a-Si∶H层组成的系统.本工作分析了Pd/a-Si∶H的界面键合状态及组分分布的变化对价带谱与芯能级谱的影响,并与Pd/C-Si系统的结果进行了比较.结果表明:Pd/a-Si∶H界面具有与Pd/C-Si界面相似的电子结构;但是,Pd原子在a-Si∶H中具有较大的扩散速率,因此,处于更富Si的环境中。     

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。     

Passivation of p-n junction in crystalline silicon by amorphous silicon

Hydrogenated amorphous silicon, a-Si:H, is shown to be an excellent passivant for crystalline silicon (c-Si) p-n junctions. A two-orders-of-magnitude reduction in reverse leakage current from that of a typical thermal oxide passivated junction is obtained. This is achieved through a lowering of the interface state density by hydrogenation of the c-Si surface. Superior bias-temperature stability of the passivated junctions also is observed. There is evidence that the hydrogen in the bulk of the a-Si:H can act as a hydrogen reservoir for rehydrogenation of the interface between c-Si and a-Si:H. Thermal stability of the a-Si:H is adequate for temperatures up to 500°C for 30 min, which is sufficient for most device-processing requirements. Above 550°C, significant dehydrogenation from both the interface and the bulk a-Si:H regions and an increase in leakage are observed. The passivation properties were assessed through studies of the current-voltage and current-temperature characteristics of the p-n junctions.     

Performance of bifacial HIT solar cells on n-type silicon substrates

The performance of amorphous silicon(a-Si:H) /crystalline silicon(c-Si) heterojunction is studied,and the effects of the emitter layer thickness,doping concentration,intrinsic layer thickness,back heavily-doped n layer,interface state and band offset on the optical and electrical performance of bifacial heterojunction with intrinsic thin-layer(HIT) solar cells on ntype silicon substrates are discussed.It is found that the HIT solar cells on n-type substrates can obtain a higher conversion efficiency than th...     

非晶硅钝化膜的热稳定性及其在可控硅元件上的应用

实验报导了α-Si:H薄膜作为优质的硅器件钝化保护膜在可控硅元件上的应用.指出,它能大幅度提高元件的正反向击穿电压,改善温度特性,具有明显的经济效益.还指出,α-Si:H钝化膜能吸取c-Si界面上的杂质进一步促使硅器件的优化.本文还讨论了提高α-Si:H钝化保护膜热稳定性的途径.     

Silicon heterojunction solar cell: a new buffer Layer concept with low-temperature epitaxial silicon

Amorphous silicon/crystalline silicon heterojunction solar cells, deposited by the plasma-enhanced chemical vapor deposition (PECVD) technique, have been fabricated using different technologies to passivate defects at the heterointerface: without treatment, the insertion of a thin intrinsic amorphous layer or that of a thin intrinsic epitaxial layer. The open circuit voltage of heterojunction solar cells fabricated including an intrinsic amorphous buffer layer is strangely lower than in devices with no buffer layer. The structure of the amorphous buffer layer is investigated by high resolution transmission electron microscope observations. As an alternative to amorphous silicon, the insertion of a fully epitaxial silicon layer, deposited at low temperature with conventional PECVD technique in a hydrogen-silane gas mixture, was tested. Using the amorphous silicon/crystalline silicon (p a-Si/i epi-Si/n c-Si) heterojunction structure in solar cells, a 13.5% efficiency and a 605-mV open circuit voltage were achieved on flat Czochralski silicon substrates. These results demonstrate that epitaxial silicon can be successfully used to passivate interface defects, allowing for an open circuit voltage gain of more than 50 mV compared to cells with no buffer layer. In this paper, the actual structure of the amorphous silicon buffer layer used in heterojunction solar cells is discussed. We make the hypothesis that this buffer layer, commonly considered amorphous, is actually epitaxial.     

非晶硅薄膜的基本性质及其在台面型硅器件上的钝化作用

利用非晶硅薄膜的半绝缘特性将它作为硅器件,尤其是台面型硅器件的钝化保护膜,经过长达两年的实验和生产上的试用,证实了它具有特殊的优点.α-Si:H薄膜中的氢能直接填补c-Si界面上的缺陷态,降低界面态密度,使器件反向漏电流大大下降,从而改善了硅器件的稳定性,提高了可靠性与成品率,具有明显的经济效益     

Simulation and optimization of dopant-free asymmetric heterojunction solar cells

In order to further study doping-free asymmetric heterojunction (DASH) solar cells, we used AFORS-HET software to optimize the structure of Al/SnO2/a-Si:H (i)/c-Si (p)/a-Si:H (i)/NiOx/Ag. In a certain adjustment range, a series of simulations were carried out on the band gap, electron affinity, thickness and work function (WF) of NiOx, thickness and WF of SnO2, and the thickness of a-Si:H (i). After the above optimization, 21.08% efficiency was obtained at 300 K. This study shows that the solar cells with this structure have good light absorption properties in a very wide spectrum. The present simulation provides instructive suggestions for follow-up experiments of DASH solar cells.     

等离子体过程不稳定性和氢处理对HIT电池界面特性影响的研究

采用等离子体增强化学气相沉积（PECVD）技术制备薄膜硅/晶体硅异质结,通过测量沉积了本征非晶硅（a-Si:H(i)）后晶体硅（c-Si）的少子寿命以及结构为Ag/a-Si:H(p)/a-Si:H(i)/c-Si(n) /Ag 异质结的暗I-V特性,研究了等离子体初期瞬态过程和氢预处理对异质结界面性质的影响。结果表明：使用挡板且当挡板时间（tS）大于100秒时,可以有效地减少等离子体初期瞬态过程对界面性质的负面影响;与热丝化学气相沉积中氢原子处理有利于界面钝化不同,PECVD中的氢等离子体处理,由于氢原子的轰击特性,对钝化可能存在一定的不利影响;最优氢预处理时间为60秒。     

The Characteristics of a Hydrogenated Amorphous Silicon Semitransparent Solar Cell When Applying n/i Buffer Layers

In this work, buffer layers with various conditions are inserted at an n/i interface in hydrogenated amorphous silicon semitransparent solar cells. It is observed that the performance of a solar cell strongly depends on the arrangement and thickness of the buffer layer. When arranging buffer layers with various bandgaps in ascending order from the intrinsic layer to the n layer, a relatively high open circuit voltage and short circuit current are observed. In addition, the fill factors are improved, owing to an enhanced shunt resistance under every instance of the introduced n/i buffer layers. Among the various conditions during the arrangement of the buffer layers, a reverse V shape of the energy bandgap is found to be the most effective for high efficiency, which also exhibits intermediate transmittance among all samples. This is an inspiring result, enabling an independent control of the conversion efficiency and transmittance.     

Nanoindentation-induced phase transformation in crystalline silicon and relaxed amorphous silicon

Nanoindentation-induced phase transformation in both crystalline silicon (c-Si) and relaxed amorphous silicon (a-Si) have been studied. A series of nanoindentations were made with a sharp diamond Berkovich tip. During nanoindentations, maximum loads were applied from 1000 to 6000 μN, with a 1000 μN/s loading rate. A slow unloading rate at 100 μN/s was chosen to favor the formation of the high-pressure polycrystalline phases (Si-III and Si-XII). A fast unloading rate within 1 s was used to obtain a-Si end phase. The nanoindentation behavior and the structure of deformation regions were examined by load–depth characteristics curves and Raman. Large differences were observed between the transformation behavior in c-Si and that in relaxed a-Si. Indentation curves in c-Si present plastic deformation curves with elbow (no pop-out) on the unloading curves, even for loads up to 9000 μN. On the other hand, indentations in relaxed a-Si give rise to the same plastic deformation as c-Si at low loads (1000–2000 μN), whereas show clear pop-outs at high loads (above 3000 μN). Raman results suggest that high-pressure phases (HPPs) can occur more easily within a relaxed a-Si matrix than in a c-Si matrix. The results suggest a significantly different indentation behavior and phase transformation sequence in c-Si and relaxed a-Si at the nanoscale.     

NIP型非晶硅薄膜太阳能电池的研究

采用射频等离子体增强化学气相沉积(RF-PECVD)技术制备非晶硅(a-Si)NIP太阳能电池,其中电池的窗口层采用P型晶化硅薄膜,电池结构为Al/glass/SnO2/N(a-Si:H)/I(a-Si:H)/P(cryst-Si:H)/ITO/Al.为了使P型晶化硅薄膜能够在a-Si表面成功生长,电池制备过程中采用了H等离子体处理a-Si表面的方法.通过调节电池P层和N层厚度和H等离子体处理a-Si表面的时间,优化了太阳能电池的制备工艺.结果表明,使用H等离子体处理a-Si表面5 min,可以在a-Si表面获得高电导率的P型晶化硅薄膜,并且这种结构可以应用到电池上;当P型晶化硅层沉积时间12.5 min,N层沉积12 min,此种结构电池特性最好,效率达6.40%.通过调整P型晶化硅薄膜的结构特征,将能进一步改善电池的性能.     

Microcrystalline Silicon Materials and Solar Cells Prepared by VHF-PECVD

A series of samples deposited by VHF - PECVD at different pressures were studied. The measurement results of photosensitivity (photo conductivity/dark conductivity) and activation energy indicaten ear the same rule with the change of the pressure. The results measured by Raman scattering spectra, X-ray diffraction and FTIR all proved the evident crystallization of the materials. Treating the p/i interface by hydrogen has a great improving effect on the performance of the microcrystalline silicon (μc-Si) p-i-n solar cells if the treatment time was appropriate. An efficiency of 4.24% for μc-Si p-i-n solar cells deposited by VHF-PECVD was firstly obtained.     

用于TFT有源层的Ar~+激光结晶a-Si:H的性质(英文)

This paper demonstrates the technological approach to the high performance a-Si:H thin film transistor (TFT) fabricated by the Ar+ laser-crystallization technique on the fused quartz substrates. The a-Si:H films for the active layer of TFT were prepared in a capacitively coupled glow-discharge deposition system. The films were crystallized by CW Ar+ laser scanning at low speeds (3-5 cm/s). The laser power ranges from 2.5W to 5.0W. The TEM cross-section micrograph illustrates that a liquid phase laser crystallization region (LP-LCR) has defect-free of structure with a grain size of the order of handreds of micron. In the Raman spectrum of LP-LCR, 475 cm-1 peak of a-Si:H disappears and 520 cm-1 peak of c-Si becomes stronger and sharper. The value of conductivity in the layer of LP-LCR is five orders of magnitude larger than the one in asepositedd a-Si:H film. We also discussed some problems to be overcome in application of a-Si : H TFTs in LCD.     

Surface morphology and I-V characteristics of single-crystal,polycrystalline, and amorphous silicon FEA's

This letter reports the surface morphology and current-voltage (I-V) characteristics of single-crystal silicon (c-Si), polycrystalline silicon (poly-Si), and amorphous silicon (a-Si) field emitter arrays (FEAs). As-deposited a-Si film has a smoother surface than poly-Si film. The surface morphology of the a-Si remains smooth even after phosphorus doping and oxidation at 950°C to be improved in emission characteristics, i.e., smaller anode current deviation among arrays smaller gate current, and higher failure voltage than those of poly-Si FEAs. Such improved characteristics can be explained by the smooth surface morphology which is kept during doping and oxidation. The surface roughness and emission characteristics of a-Si FEAs are comparable to those of c-Si FEAs