For none, one, or two polarities—How do POLO junctions fit best into industrial Si solar cells?

We present a systematic study on the benefit of the implementation of poly-Si on oxide (POLO) or related junctions into p-type industrial Si solar cells as compared with the benchmark of Passivated Emitter and Rear Cell (PERC). We assess three aspects: (a) the simulated efficiency potential of representative structures with POLO junctions for none (=PERC+), one, and for two polarities; (b) possible lean process flows for their fabrication; and (c) experimental results on major building blocks. Synergistic efficiency gain analysis reveals that the exclusive suppression of the contact recombination for one polarity by POLO only yields moderate efficiency improvements between 0.23%abs and 0.41%abs as compared with PERC+ because of the remaining recombination paths. This problem is solved in a structure that includes POLO junctions for both polarities (POLO2), for whose realization we propose a lean process flow, and for which we experimentally demonstrate the most important building blocks. However, two experimental challenges—alignment tolerances and screen-print metallization of p+ poly-Si—are unsolved so far and reduced the efficiency of the “real” POLO2 cell as compared with an idealized scenario. As an intermediate step, we therefore work on a POLO IBC cell with POLO junctions for one polarity. It avoids the abovementioned challenges of the POLO2 structure, can be realized within a lean process flow, and has an efficiency benefit of 1.59%abs as compared with PERC—because not only contact recombination is suppressed but also the entire phosphorus emitter is replaced by an n+ POLO junction

Impact of the deposition and annealing temperature on the silicon surface passivation of ALD Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e films

\u3cp\u3eThe effect of the deposition and annealing temperature on the surface passivation of atomic layer deposited Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e films was investigated on n-type Cz silicon wafers. The deposition temperature was varied between 200 and 500°C and the annealing temperature between 300 and 450°C, respectively. Films prepared at 200 and 300°C showed an improvement of surface passivation with increasing anneal temperature. The Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e films grown at 400 and 500°C did not improve by annealing. By corona charging experiments it was revealed that the improvement in surface passivation with increasing anneal temperature of films grown at 300°C can be attributed to a significant increase in chemical passivation with a minor increase in field-effect passivation. For Cz and FZ wafers an identical surface passivation was achieved with the chemical passivation being lower for Cz wafers due to the surface morphology and the field-effect passivation being quite similar. Consequently the field-effect passivation was found to be the more important passivation mechanism.\u3c/p\u3

High surface passivation quality and thermal stability of ALD Al2O3 on wet chemical grown ultra-thin SiO2 on silicon

AbstractIn this work we present the surface passivation properties of pre-oxidized Si(100) surfaces compared to H-terminated Si(100) after atomic layer deposition (ALD) of Al2O3 thin films. Additionally the differences in surface passivation for n- and p-type silicon were investigated. The pre-oxidation was carried out in three different wet chemical solutions: (a) nitric acid (HNO3), (b) hydrochloric acid mixed with hydrogen peroxide (HCl/H2O2) and (c) a sulphuric acid with hydrogen peroxide (H2SO4/H2O2). The surface passivation quality was determined directly after deposition, after anneal at 400°C in N2 atmosphere for 10min and after direct firing at 850°C in ambient for several seconds. Directly after deposition we find significantly higher passivation quality for the Al2O3 passivated samples with pre-oxidized surfaces than for H-terminated surfaces. After anneal and after directly firing the passivation quality for Al2O3 on H-terminated surfaces is slightly better, nevertheless the surface recombination velocity for Al2O3 on pre-oxidized silicon surfaces is still<15cm/s for n-type Fz silicon and<70cm/s for p-type Cz. A high quality surface passivation can therefore be achieved for silicon pre-oxidized with wet chemistries. The field-effect passivation for HF-last ALD Al2O3 exceeds the level of pre-oxidized samples after anneal as well as after direct firing

High surface passivation quality and thermal stability of ALD Al2O3 on wet chemical grown ultra-thin SiO2 on silicon

In this work we present the surface passivation properties of pre-oxidized Si(100) surfaces compared to H-terminated Si(100) after atomic layer deposition (ALD) of Al2O3 thin films. Additionally the differences in surface passivation for n- and p-type silicon were investigated. The pre-oxidation was carried out in three different wet chemical solutions: (a) nitric acid (HNO3), (b) hydrochloric acid mixed with hydrogen peroxide (HCl/H2O2) and (c) a sulphuric acid with hydrogen peroxide (H2SO4/H2O2). The surface passivation quality was determined directly after deposition, after anneal at 400 °C in N2 atmosphere for 10 min and after direct firing at 850 °C in ambient for several seconds. Directly after deposition we find significantly higher passivation quality for the Al2O3 passivated samples with pre-oxidized surfaces than for H-terminated surfaces. After anneal and after directly firing the passivation quality for Al2O3 on H-terminated surfaces is slightly better, nevertheless the surface recombination velocity for Al2O3 on pre-oxidized silicon surfaces is still &lt;15 cm/s for n-type Fz silicon and &lt;70 cm/s for p-type Cz. A high quality surface passivation can therefore be achieved for silicon pre-oxidized with wet chemistries. The field-effect passivation for HF-last ALD Al2O3 exceeds the level of pre-oxidized samples after anneal as well as after direct firing

MRI Response Assessment in Glioblastoma Patients Treated with Dendritic-Cell-Based Immunotherapy

Introduction: In this post hoc analysis we compared various response-assessment criteria in newly diagnosed glioblastoma (GB) patients treated with tumor lysate-charged autologous dendritic cells (Audencel) and determined the differences in prediction of progression-free survival (PFS) and overall survival (OS). Methods: 76 patients enrolled in a multicenter phase II trial receiving standard of care (SOC, n = 40) or SOC + Audencel vaccine (n = 36) were included. MRI scans were evaluated using MacDonald, RANO, Vol-RANO, mRANO, Vol-mRANO and iRANO criteria. Tumor volumes (T1 contrast-enhancing as well as T2/FLAIR volumes) were calculated by semiautomatic segmentation. The Kruskal-Wallis-test was used to detect differences in PFS among the assessment criteria; for correlation analysis the Spearman test was used. Results: There was a significant difference in median PFS between mRANO (8.6 months) and Vol-mRANO (8.6 months) compared to MacDonald (4.0 months), RANO (4.2 months) and Vol-RANO (5.4 months). For the vaccination arm, median PFS by iRANO was 6.2 months. There was no difference in PFS between SOC and SOC + Audencel. The best correlation between PFS/OS was detected for mRANO (r = 0.65) and Vol-mRANO (r = 0.69, each p < 0.001). A total of 16/76 patients developed a pure T2/FLAIR progressing disease, and 4/36 patients treated with Audencel developed pseudoprogression. Conclusion: When comparing different response-assessment criteria in GB patients treated with dendritic cell-based immunotherapy, the best correlation between PFS and OS was observed for mRANO and Vol-mRANO. Interestingly, iRANO was not superior for predicting OS in patients treated with Audencel

Audencel Immunotherapy Based on Dendritic Cells Has No Effect on Overall and Progression-Free Survival in Newly Diagnosed Glioblastoma: A Phase II Randomized Trial

Dendritic cells (DCs) are antigen-presenting cells that are capable of priming anti-tumor immune responses, thus serving as attractive tools to generate tumor vaccines. In this multicentric randomized open-label phase II study, we investigated the efficacy of vaccination with tumor lysate-charged autologous DCs (Audencel) in newly diagnosed glioblastoma multiforme (GBM). Patients aged 18 to 70 years with histologically proven primary GBM and resection of at least 70% were randomized 1:1 to standard of care (SOC) or SOC plus vaccination (weekly intranodal application in weeks seven to 10, followed by monthly intervals). The primary endpoint was progression-free survival at 12 months. Secondary endpoints were overall survival, safety, and toxicity. Seventy-six adult patients were analyzed in this study. Vaccinations were given for seven (3–20) months on average. No severe toxicity was attributable to vaccination. Seven patients showed flu-like symptoms, and six patients developed local skin reactions. Progression-free survival at 12 months did not differ significantly between the control and vaccine groups (28.4% versus 24.5%, p = 0.9975). Median overall survival was similar with 18.3 months (vaccine: 564 days, 95% CI: 436–671 versus control: 568 days, 95% CI: 349–680; p = 0.89, harzard ratio (HR) 0.99). Hence, in this trial, the clinical outcomes of patients with primary GBM could not be improved by the addition of Audencel to SOC