PERCIGS

PercIGS

 Partecipanti

Mappa

 Word cloud

Esplora la "nuvola delle parole (Word Cloud) per avere un'idea di massima del progetto.

 Obiettivo del progetto (Objective)

'To a large extent, the latest CIGS improvement is due to enhancements in the semiconductor material quality. However, as the material quality of the semiconductors improves, other parts of the solar cell are becoming the new bottlenecks to increase the efficiency further towards the theoretical limit for non-concentrated light, which is 30 %. Therefore, this project is focused on an advanced, yet industrially feasible, device structure: The introduction of point contacts and a passivation layer will be used to reduce the back contact recombination and thus enhance efficiency. The application focuses towards CIGS based solar cells, but the concept can be generalized to other high quality thin film solar cell technologies as well. The project is structured in four sub-projects, of which the motivations are described below.

Specific goals: • An innovative concept to reduce the high recombination back contact surface area will be developed. This will drastically reduce the recombination rate at the back contact for state of the art CIGS solar cells • Increase of solar cell efficiency by up to 1.5 absolute percent by increasing photo-generated voltage and current. • The concept will also be used as a powerful tool to investigate the influence of grain boundaries in the polycrystalline CIGS semiconductor material.

The project has four main objectives: (1) point contact development, (2) assessment of passivation layers, (3) application in solar cell devices, and (4) a CIGS material study.

A successful outcome will advance the current state-of-the-art in CIGS research, through: • New methods to develop nano-sized contacting points • Novel (rear) passivation layers for CIGS material • An advanced device structure to increase CIGS solar cell efficiency • Improved understanding of the influence of grain boundaries on charge transport in CIGS material'

Introduzione (Teaser)

Solar cells generate electricity by exploiting the electron-hole pairs created by incident photons. The concepts exploited in PERCIGS effectively hinder loss of electrons by recombination at the back contact, thereby improving both voltage and current in CIGS solar cells

Descrizione progetto (Article)

Thin-film solar cells made of copper indium gallium selenide (CIGS) have achieved major improvements in efficiencies largely due to enhancements in materials properties. As the margin for improvement based solely on materials narrows, EU-funded scientists working on the project 'PercIGS' (PERCIGS) set out to develop a new device structure to push efficiency toward its theoretical limits. The focus was on reducing surface recombination of the charge carriers at the rear contact where recombination rates are typically high.

The structure of the surfaces and interfaces plays an important role in recombination. The silicon solar cell industry has benefited from a rear surface passivation layer (a coating to make the surface less reactive, more passive) with micron-sized point openings. Inspired by the concept, PERCIGS scientists introduced a surface passivation layer with nano-scale contacts to CIGS thin-film solar cells to solve the recombination problem. Three different methodologies were used to incorporate 2D passivation layers in CIGS solar cells.

Two industrially practical approaches were developed as proof-of-principle and one model test set-up was created as well. The industrially viable technologies employed aluminium oxide as the passivation layer but differed in the method of contacting. One used local point contacts formed by precipitation of nanospheres during chemical bath deposition of cadmium sulphide. The other used molybdenum nanoparticles grown in highly ionised pulsed plasma.

When incorporated into CIGS solar cells with ultra-thin absorber layers, solar cell efficiency increased due to improved passivation and optical confinement. Novel nano-scale contacts were also created using electron beam lithography. These similarly enhanced solar cell efficiency and will be an excellent model for the study of new concepts.

The pioneering work resulted in several invited oral presentations at international conferences and articles in prestigious peer-reviewed scientific journals. While focused on thin-film CIGS solar cells, it is easily adapted to other thin-film technologies. The future appears to be bright for the new solar cell rear contact passivation techniques with potential benefits for manufacturers, consumers and the environment.