Development of titanium oxide thin film as electron selective passivating contact in N-type silicon solar cells

NASER BEYRAGHI

Development of titanium oxide thin film as electron selective passivating contact in N-type silicon solar cells

Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Türkiye

Tezin Onay Tarihi: 2024

Tezin Dili: İngilizce

Öğrenci: NASER BEYRAGHI

Asıl Danışman (Eş Danışmanlı Tezler İçin): SELÇUK YERCİ

Danışman: Raşit Turan

Özet:

Currently, the main concern in the PV technology development is to enhance power conversion efficiency and minimize production costs, with the aim of lowering the levelized cost of electricity to a more affordable level. The emergence of the carrierselective passivating contacts (CSPCs) concept was a milestone for silicon PV technology to push single-junction solar cell efficiency toward the ShockleyQueisser limit further. Due to issues regarding Si-based CSPCs, there is growing interest in developing high-efficiency dopant-free alternatives that are compatible with simpler fabrication techniques. The objective of this thesis is to optimize and characterize the performance of a solution-processed TiOx thin film intended for use as an effective ESPC for n-type silicon solar cell applications. Our experimental design is based on two routes to identify the optimal processing conditions. Benefiting the low-temperature processing conditions proposed by the first route, excellent surface passivation (iVoc: 706 mV) and low contact resistivity (𝜌c: 45 mΩ.cm2) can be achieved simultaneously. Moreover, the second route allowed us to achieve an outstanding iVoc of 726 mV and 𝜌c of 8.74 mΩ·cm2 simultaneously by eliminating any ex- or in-situ annealing step. The proposed routes, establishing a new benchmark for solution-processed ESPCs that is on par with the state-of-the-art TiOx-based ESPCs deposited by ALD technique, introducing a novel opportunity to advance the development of simple-processed high-efficiency crystalline silicon (cSi) solar cells. Moreover, we demonstrate a champion cell with an efficiency of 18.55% with a hybrid structure. In addition, to gain a thorough understanding of the underlying mechanism of the impressive achievements, we present comprehensive structural, chemical, optical, and electrical characterizations, which have been evaluated and extensively discussed in this thesis.