PbTe Kuantum Noktalar ve Fotovoltaik Uygulamalarda Bant Enerji Hizalamasının Yapılması

Kurşun tellür (PbTe) kuantum noktaları yüksek çoklu eksiton üretim verimine sahip olmaları nedeniyle fotovoltaik uygulama alanları için gelecek vaat eden adaylar olarak değerlendirilseler de görece daha az araştırılmış yüzey kimyaları ve atmosferik ortama olan hassasiyetleri sebebiyle güneş gözesi tasarımlarında sınırlı alaka görmektedirler. Bu çalışma, yüksek kristalli yapıya sahip PbTe kuantum noktalarının sentezini, karakterizasyonunu ve bant hizalama vasıtasıyla solüsyon bazlı güneş gözelerinde kullanımını konu almaktadır. Ultraviyole fotoelektron spektroskopisi çalışmaları, iletim ve değerlik bant seviyelerinin ligant değişimi işleminde kullanılan ligant türüne bağlı olduğunu göstermiştir. Tetrabütilamonyum iyodür (TBAI) ve 1,2-etanditiyol (EDT) ligantlarına tabi tutulmuş PbTe kuantum noktalarının vakuma karşı iletim ve değerlik bant seviyeleri sırasıyla -3,73 eV/-4,83 eV ve -3,48 eV/-4,45 eV olarak belirlenmiştir. TBAI ve EDT ligantlarıyla işlenmiş tabakaların arasında bulunan bant ofseti, güneşi soğuran tabakada bant hizalamasını gerçekleştirebilmemize olanak sağlamıştır. Sonuç olarak, TBAI ve EDT ligantları ile işlem görmüş kuantum noktalarının birlikte kullanıldığı çift katmanlı göze mimarisine sahip güneş gözeleri %0.65 foton değiştirme verimine ulaşmıştır.

Anahtar Kelimeler:

Kurşun telllür, PbTe kuantum nokta, Güneş hücresi, TBAI, Bant hizalama

PbTe Quantum Dots and Engineering of the Energy Band Alignment in Photovoltaic Applications

Lead telluride (PbTe) quantum dots, despite being considered as one of the most promising candidates for future photovoltaics owing to their higher multiple exciton generation yields, have received limited attention in solar cell designs due their less explored surface chemistry and high air sensitivity. This study demonstrates the synthesis and characterization of highly crystalline PbTe QDs and their utilization in solution processed solar cells through band alignment engineering. Ultraviolet photoelectron spectroscopy studies showed that the conduction and valence band levels depend strongly on the type of surface ligand utilized for the ligand exchange process. Conduction and valence band levels of tetrabutylammonium iodide (TBAI) and 1,2-ethanedithiol (EDT) treated PbTe QDs with respect to vacuum were measured as -3.73 eV/-4.83 eV and -3.48 eV/-4.45 eV, respectively. The presence of a band offset between the conduction and valence band levels of TBAI and EDT treated layers allowed us to engineer the band alignment in the light absorbing layer. As a result, solar cells where TBAI and EDT ligand treated QDs were utilized in a bilayer cell architecture reached a photo conversion efficiency of 0.65%.

Keywords:

Lead telluride, PbTe quantum dots, Solar cells, TBAI, Band alignment,

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