It has been recognized for some time that the spontaneous emission by atoms is not necessarily a fixed and immutable property of the coupling between matter and space, but that it can be controlled by modification of the properties of the radiation field. This is equally true in the solid state, where spontaneous emission plays a fundamental role in limiting the performance of semiconductor lasers, heterojunction bipolar transistors, and solar cells. If a three-dimensionally periodic dielectric structure has an electromagnetic band gap which overlaps the electronic band edge, then spontaneous emission can be rigorously forbidden.

https://link.aps.org/pdf/10.1103/PhysRevLett.58.2059

Inhibited Spontaneous Emission in Solid-State Physics and Electronics

The efficiency of silicon solar cells has a large influence on the cost of most photovoltaics panels. Here, researchers from Kaneka present a silicon heterojunction with interdigitated back contacts reaching an efficiency of 26.3% and provide a detailed loss analysis to guide further developments.

Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26

The path towards a high-performance solution-processed kesterite solar cell ☆

The light trapping properties of textured optical sheets have become of recent interest in photovoltaic energy conversion since light trapping allows a significant reduction in the thickness of active solar cell material. Previous analyses have concentrated on sheets with randomly textured (Lambertian) surfaces. The texturing of crystalline silicon substrates with anisotropic etches to give surfaces covered by square based pyramids defined by intersecting (111) crystallographic planes is a widely used technique for reflection control in silicon solar cells. This paper analyzes the light trapping properties of substrates with such pyramidally textured surfaces. Important differences are found from the case of Lambertian surfaces with practical consequences for the design of high efficiency silicon solar cells.

Light trapping properties of pyramidally textured surfaces

The efficiency of solar cells with high-area, nanostructured surfaces is limited by surface and Auger charge-recombination processes, which can be slowed through appropriate levels of junction doping

An 18.2%-efficient black-silicon solar cell achieved through control of carrier recombination in nanostructures

A simple method for implementing the steady‐state photoconductance technique for determining the minority‐carrier lifetime of semiconductor materials is presented. Using a contactless instrument, the photoconductance is measured in a quasi‐steady‐state mode during a long, slow varying light pulse. This permits the use of simple electronics and light sources. Despite its simplicity, the technique is capable of determining very low minority carrier lifetimes and is applicable to a wide range of semiconductor materials. In addition, by analyzing this quasi‐steady‐state photoconductance as a function of incident light intensity, implicit current–voltage characteristic curves can be obtained for noncontacted silicon wafers and solar cell precursors in an expedient manner.

/pdf/contactless-determination-of-current-voltage-characteristics-le6nm5iqvm.pdf

Contactless determination of current–voltage characteristics and minority‐carrier lifetimes in semiconductors from quasi‐steady‐state photoconductance data

This paper describes a new method for minority-carrier lifetime determination using a contactless photoconductance instrument in a quasi-steady-state mode. Compared to the more common transient photoconductance decay approach, the new technique permits the use of simpler electronics and light sources, yet has the capability to measure lifetimes in the nanosecond to millisecond range. In addition, by analyzing the quasi-steady-state photoconductance as a function of incident light intensity, an implicit I/sub SC/-V/sub OV/ curve can be obtained for noncontacted silicon wafers and solar cell precursors.

Quasi-steady-state photoconductance, a new method for solar cell material and device characterization

A quasi-steady-state open-circuit voltage method for solar cell characterization

Solar energy has the potential to play a central role in the future global energy system because of the scale of the solar resource, its predictability, and its ubiquitous nature. Global installed solar photovoltaic (PV) capacity exceeded 500 GW at the end of 2018, and an estimated additional 500 GW of PV capacity is projected to be installed by 2022–2023, bringing us into the era of TW-scale PV. Given the speed of change in the PV industry, both in terms of continued dramatic cost decreases and manufacturing-scale increases, the growth toward TW-scale PV has caught many observers, including many of us (1), by surprise. Two years ago, we focused on the challenges of achieving 3 to 10 TW of PV by 2030. Here, we envision a future with ∼10 TW of PV by 2030 and 30 to 70 TW by 2050, providing a majority of global energy. PV would be not just a key contributor to electricity generation but also a central contributor to all segments of the global energy system. We discuss ramifications and challenges for complementary technologies (e.g., energy storage, power to gas/liquid fuels/chemicals, grid integration, and multiple sector electrification) and summarize what is needed in research in PV performance, reliability, manufacturing, and recycling.

https://science.sciencemag.org/content/sci/364/6443/836.full.pdf

Terawatt-scale photovoltaics: Transform global energy

Boron-doped crystalline silicon is the most relevant material in today's solar cell production. Following the trend towards higher efficiencies, silicon substrate materials with high carrier lifetimes are becoming more and more important. In silicon with sufficiently low metal impurity concentrations, the carrier lifetime is ultimately limited by a metastable boron–oxygen-related defect, which forms under minority-carrier injection. We have analysed 49 different Czochralski-grown silicon materials of numerous suppliers with various boron and oxygen concentrations. On the basis of our measured lifetime data, we have derived a universal empirical parameterisation predicting the stable carrier lifetime from the boron and oxygen content in the crystalline silicon material. For multicrystalline silicon it is shown that the predicted carrier lifetime can be regarded as a fundamental upper limit. Copyright © 2005 John Wiley & Sons, Ltd.

Ronald A. Sinton

Papers

Contactless determination of current–voltage characteristics and minority‐carrier lifetimes in semiconductors from quasi‐steady‐state photoconductance data

Quasi-steady-state photoconductance, a new method for solar cell material and device characterization

A quasi-steady-state open-circuit voltage method for solar cell characterization

Terawatt-scale photovoltaics: Transform global energy

Fundamental boron-oxygen-related carrier lifetime limit in mono- and multicrystalline silicon