Identification of defective regions in thin-film Si solar cells for new-generation energy devices

Abstract

We developed a high-conversion-efficiency, a-Si/IlC Si tandem solar module using Ilc-Si thin film on a Gen. 5 class glass substrate. The stabilized module efficiency was 10.7% (initial module efficiency: 12.0%). We prepared high performance a-Si/Jlc-Si tandem solar cells based on our original technology for J.1c-Si thin films with localized plasma confinement chemical vapor deposition, optical confinement techniques, and laser patterning. To obtain higher conversion efficiency, optical confinement techniques are crucial, especially transparent conductive oxide (TCO) controlling technology. However, high-performance TCO includes steep valleys in the texture structure. Therefore, many defective regions are generated in the deposition of Jlc-Si thin film that degrade the solar cell performance. In this study we structurally identified these defective regions and propose a new formation model of the defective regions.

Review of thin-film silicon deposition techniques for high-efficiency solar cells developed at Panasonic/Sanyo

“…To achieve large-area and high-rate deposition of μc-Si film by generating stable and uniform SiH 4 plasma in the high-pressure range of over 1000 Pa, we have been developing a unique process that we term "localized plasma confinement (LPC) CVD" [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Fig.…”

“…5 shows the I-V characteristics of an a-Si/mc-Si tandem solar module (G5 size). An initial module efficiency of 12.0% and a stabilized module efficiency of 10.7% were achieved [16][17][18][19][20][21][22][23][24]. We are also studying very high-efficiency small-area cells.…”

“…6 shows the I-V characteristics of an a-Si/mc-Si tandem solar cell (1 cm 2 ). The initial conversion efficiency of 13.5% (Voc: 1.41 V, Jsc: 12.7 mA/cm 2 , and FF: 0.754) and a stabilized conversion efficiency of 12.2% have been achieved for a small cell (area: 1 cm 2 ) [16][17][18][19][20][21][22][23][24]. The stabilized efficiency was among the highest values achieved for a-Si/μc-Si tandem solar cells.…”

Intermittent Very High Frequency Plasma Deposition on Microcrystalline Silicon Solar Cells Enabling High Conversion Efficiency

“…A defective region is affected by the underlying shape or the underlying film quality. It has been reported that the defective region consists of vacancies and a low-density amorphous region [2]. Previously, we proposed another factor for the formation of a defective region due to the shadowing effect on incident radicals [2], which should reduce the X c [8].…”

“…This is because a defective component in the µc-Si:H film is affected by transparent conductive oxide (TCO) texture, as the film thickness of the microcrystalline silicon increases [2]. To avoid a defective region being formed and achieve high conversion efficiency (Eff ), the surface morphology of TCO was modified to have a blunt angle or rounded shape [3].…”