Improved Rear Surface Passivation of Cu(In,Ga)Se2 Solar Cells : A Combination of an Al2O3 Rear Surface Passivation Layer and Nano-Sized Local Rear Point Contacts

• An innovative rear contacting structure for copper indium gallium (di) selenide (CIGS) thin-film solar cells is developed in an industrially viable way and demonstrated in tangible devices. The idea stems from the silicon (Si) industry, where rear surface passivation layers are combined with micron-sized local point contacts to boost the open-circuit voltage (VOC) and, hence, cell efficiency. However, compared with Si solar cells, CIGS solar cell minority carrier diffusion lengths are several orders lower in magnitude. Therefore, the proposed CIGS cell design reduces rear surface recombination by combining a rear surface passivation layer and nanosized local point contacts. Atomic layer deposition of Al2O3 is used to passivate the CIGS surface and the formation of nanosphere-shaped precipitates in chemical bath deposition of CdS to generate nanosized point contact openings. The manufactured Al2O3 rear surface passivated CIGS solar cells with nanosized local rear point contacts show a significant improvement in VOC compared with unpassivated reference cells.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Energisystem (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Energy Systems (hsv//eng)

Nyckelord

Solar cells

Photovoltaics

Si

PERC

PERL

Thin film

Cu(In

Ga)Se2

CIGS

Ga grading

Rear surface passivation

Al2O3

Atomic layer deposition

Point contact openings

Nano-sized

Engineering Science with specialization in Electronics

Teknisk fysik med inriktning mot elektronik

Teknisk fysik med inriktning mot fasta tillståndets fysik

Engineering Science with specialization in Solid State Physics

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