Improvement in Performance of A-SiGe:H Solar Cells for Multi-Junction Cells

Abstract

The quality of a-SiGe:H film was improved by considering the effects of substrate temperature and deposition rate on film properties. Accurate measurement of the optical gap and the film composition of Si, Ge and H made it possible to formulate the optical gap using a linear function of bonded H content (CH) and Ge content (CGE). It was found for the first time that, when the optical gap is fixed to a certain value, the optimum compositions of CHAand CGe exist for high-quality a-SiGe:H. Based on these, we obtained the world's highest conversion efficiency of 3.7 % under red light (AM-1.5, 100mW/cm2 through an R65 filter which allows passage of longer wavelength (>650nm) light) for a 1cm2 a-SiGe single-junction cell. Long-term stability of the cell was also improved.

Electrical and optical properties of plasma-deposited a-SiGe:H alloys: Role of growth temperature and postgrowth anneal

“…This observation is in good agreement with the data reported by Maruyama et al 18 The growth rate for our a-SiGe:H alloys was always below 3 nm/min and therefore we can assume that the change in the optical gap at increased growth tem- peratures is not caused by the change of the Ge content in the films.…”

The Effect of Bandgap Graded Absorber on the Performance of a-Si1–xGex:H Single-Junction Cells withμc-SiOx:HN-Type Layer

“…The biased quantum efficiency serves as an important tool in the investigation of carrier collection losses in a-Si 1−x Ge x :H single-junction cells [15]. This approach would give us physical insight into the correlation among carrier collection, carrier generation, and bandgap grading width in the absorber.…”

“…Guha et al have reported that the employment of bandgap graded layers in the absorber can facilitate carrier collection, strengthen the built-in electric field, and thus improve the cell efficiency [10]. Several groups have reported the optimized bandgap grading structure in a-Si 1−x Ge x :H absorber with a-Si:H n-layer through numerical simulation approaches [11][12][13][14][15][16]. However, there are still possibilities in designing the graded bandgap structure.…”

Improvement in the spectral response at long wavelength of a-SiGe:H solar cells by exponential band gap design of the i-layer

“…Mainly two types of profiles have been investigated. The U-shape grading of the i-layer [1] leads to a better performance of the cell, by reducing the recombination at the p/i and i/n interfaces. The V-shape grading of the i-layer [2,3] reduces the trapped charge concentration and lowers the recombination losses by diminishing the average amount of Ge alloying.…”