Abstract

Atomic layer deposition (ALD) is emerging technology for the growth of thin films with excellent conformity and thickness control down to atomic levels. These unique features can be beneficial for lots of applications in photovoltaics, such as buffer layers, interface layers, transparent front contacts, photoanodes and surface passivation layers. Herein, we introduce the capability of ALD for photovoltaics in our lab: i) to coat high-aspect ratio surfaces with high-quality layers of Al₂O₃ as the passivation layer on Si NWs-array-textured c-Si solar cells. The layers of about 20 nm are sufficient to drastically reduce the surface recombination velocity at the interface resulting in solar cells with improved efficiency; ii) the use of ALD to fabricate Mg-doped and S-doped ZnO layers performing the combination of good conductivity and high transmission, potential for the alternatives to CdS as the buffer layers in CIGS thin film solar cells; iii) Cu₂ZnSnS₄ (CZTS) thin films are synthesized by alternating exposures to complementary chemical precursor vapors in an ALD system. The as-received CZTS thin films with columnar crystalline are dense, uniform and void-free. From the optical absorption spectra, the bandgap of the ALD derived CZTS thin films is in the range from 1.2 to 1.8 eV, indicating it can be used as a good absorber for solar cells. Challenges and prospects of ALD for photovoltaics are also discussed.

© 2015 Optical Society of America