There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

With a global market share of about 90%, crystalline silicon is by far the most important photovoltaic technology today. This article reviews the dynamic field of crystalline silicon photovoltaics from a device-engineering perspective. First, it discusses key factors responsible for the success of the classic dopant-diffused silicon homojunction solar cell. Next it analyzes two archetypal high-efficiency device architectures – the interdigitated back-contact silicon cell and the silicon heterojunction cell – both of which have demonstrated power conversion efficiencies greater than 25%. Last, it gives an up-to-date summary of promising recent pathways for further efficiency improvements and cost reduction employing novel carrier-selective passivating contact schemes, as well as tandem multi-junction architectures, in particular those that combine silicon absorbers with organic–inorganic perovskite materials.

/pdf/high-efficiency-crystalline-silicon-solar-cells-status-and-47y1w8zg6w.pdf

High-efficiency crystalline silicon solar cells: status and perspectives

Ultrathin solar cells with thicknesses at least 10 times lower than conventional solar cells could have the unique potential to efficiently convert solar energy into electricity while enabling material savings, shorter deposition times and improved carrier collection in defective absorber materials. Efficient light absorption and hence high power conversion efficiency could be retained in ultrathin absorbers using light-trapping structures that enhance the optical path. Nevertheless, several technical challenges prevent the realization of a practical device. Here we review the state-of-the-art of c-Si, GaAs and Cu(In,Ga)(S,Se)2 ultrathin solar cells and compare their optical performances against theoretical light-trapping models. We then address challenges in the fabrication of ultrathin absorber layers and in nanoscale patterning of light-trapping structures and discuss strategies to ensure efficient charge collection. Finally, we propose practical architectures for ultrathin solar cells that combine photonic and electrical constraints, and identify future research directions and potential applications of ultrathin photovoltaic technologies. Ultrathin solar cells attract interest for their relatively low cost and potential novel applications. Here, Massiot et al. discuss their performance and the challenges in the fabrication of ultrathin absorbers, patterning of light trapping structures and ensuring efficient charge-carrier collection.

/pdf/progress-and-prospects-for-ultrathin-solar-cells-3xb9asgl34.pdf

Progress and prospects for ultrathin solar cells

https://iopscience.iop.org/article/10.1088/1361-6641/aad655/pdf

How to control defect formation in monolithic III/V hetero-epitaxy on (100) Si? A critical review on current approaches

Thin crystalline silicon solar cells have the potential to achieve high efficiency due to the potential for increased voltage. Thin silicon wafers are fragile; therefore, means of support must be provided. This paper reports the design, development, and analysis of an 18-μm crystalline silicon solar cell electrically integrated with a steel alloy substrate. This ultrathin silicon is epitaxially grown on porous silicon and then transferred onto the steel substrate. This method allows the independent processing of each surface. The steel substrate enables robust handling and provides a conductive back plane. Three groups of cells with planar and textured structures are compared; significant improvements in J
 sc
, V
 oc
, and fill factor (FF) are achieved. The best cell shows an efficiency of 16.8% with an open-circuit voltage of 632 mV and a short-circuit current density of 34.5 mA/cm
 2
.

Development of a 16.8% Efficient 18-μm Silicon Solar Cell on Steel

This paper introduces the modeling developed to assess the potential of a III–V/SiGe tandem device. Demonstration of value will be executed via materials and solar cell device models. III–V top cell candidates are evaluated and a high-value composition is identified. Initial windowless GaAsP solar cells demonstrate a bandgap-voltage offset of 0.58.

Andrew Gerger

Papers

Development of a 16.8% Efficient 18-μm Silicon Solar Cell on Steel

Analysis of tandem III–V/SiGe devices grown on Si

Tandem GaAsP/SiGe on Si solar cells

Design, fabrication and analysis of germanium: silicon solar cell in a multi-junction concentrator system

Current matched three-terminal dual junction GaAsP/SiGe tandem solar cell on Si