Tuning CdSeTe/Sb stack properties through optimized pre-treatment processes

Öz

This work explores the impact of pre-treatment strategies on the compositional, structural, and electrical characteristics of CdSeTe/Sb stacks subjected to heat treatment prior to Sb incorporation. As-deposited and thermally pre-annealed CdSeTe/Sb samples retain near-target Se/(Se+Te) ratios (~0.19), whereas CdCl2 treatment induces partial Se redistribution (Se/(Se+Te)≈0.16), suggesting enhanced interdiffusion that may affect chalcogen-related defect states. Microstructural analysis shows that CdCl2 activation promotes recrystallization, enlarges grain size up to 6.4 µm, and drives a texture change from (220) to the thermodynamically stable (111) orientation, with minor oxide formation. Band gap values remain around 1.4 eV for all samples. Electrical measurements reveal that carrier dynamics are strongly affected by defect-mediated activation: the as-deposited sample exhibits high carrier concentration (NCV=1.5×1016 cm-3) but moderate mobility (µ=3.5×102 cm2/V.s), whereas pre-annealing enhances mobility and lowers carrier concentration (µ=3.6×103 cm2/V.s, NCV=1.7×1015 cm-3). Interestingly, CdCl2 pre-treatment slightly reduces carrier mobility while simultaneously increasing the carrier concentration (NCV =2.6×1015 cm-3), highlighting a trade-off between mobility and carrier activation. These results demonstrate that pre-treatment prior to Sb deposition in CdSeTe/Sb stacks critically governs carrier transport and electrical behavior, with direct implications for enhancing potential photovoltaic performance.

Anahtar Kelimeler

• CdSeTe/Sb
• pre-treatment
• CdCl2
• thermal annealing
• carrier concentration
• carrier mobility

Teşekkür

A. Çiriş gratefully acknowledges the financial support provided by the Scientific and Technological Research Council of Türkiye (TÜBİTAK) and the University of Delaware, Institute of Energy Conversion (IEC), for material preparation and characterization.

Optimize edilen ön işlem süreçleri ile CdSeTe/Sb katmanlı film özelliklerinin ayarlanması

Öz

Bu çalışma, CdSeTe/Sb katmanlı film yapılarında Sb tabakası kaplanmadan önce uygulanan ön-işlem stratejilerinin numunelerin kompozisyon, yapısal ve elektriksel özellikleri üzerindeki etkilerini incelemektedir. Ön-ısıl işlem uygulanmayan (CST-Ad) ve ön-tavlama işlemi uygulanan (CST-PA) numunelerde, hedeflenen Se/(Se+Te) oranına (~0.19) yakın değerler elde edilirken; CdCl2 işlemi, Se’nin kısmi yeniden dağılımına (Se/(Se+Te) ≈ 0.16) yol açmakta ve bu durum Se kaynaklı kusur durumlarını etkileyebilen difüzyon artışına işaret etmektedir. Mikroyapısal analizler, CdCl2 aktivasyonunun yeniden kristallenmeyi teşvik ettiğini, tane boyutunu 6.4 µm’ye kadar büyüttüğünü ve (220) tercihli yöneliminden termodinamik olarak kararlı (111) yönüne geçişi sağladığını, ayrıca küçük miktarda oksit oluşumuna neden olduğunu göstermektedir. Tüm numunelerde bant aralığı, yaklaşık 1.4 eV civarında kalmaktadır. Elektriksel ölçümler, taşıyıcı dinamiklerinin kusur kaynaklı aktivasyonlardan güçlü şekilde etkilendiğini göstermektedir: Ön-işlem uygulanmayan CST-Ad numunesi yüksek taşıyıcı konsantrasyonu (NCV=1.5×1016 cm-3) ancak ortalama bir mobilite (µ=3.5×102 cm2/V.s) özelliği sergilerken; ön-tavlanan CST-PA numunesinde mobilite artarken, taşıyıcı konsantrasyonu düşmektedir (µ=3.6×103 cm2/V.s, NCV=1.7×1015 cm-3). İlginç bir şekilde, CdCl2 ön-ısıl işlemi, taşıyıcı mobilitesinin kısmen azalmasına, taşıyıcı konsantrasyonun ise aynı anda kısmen artmasına yol açmaktadır (NCV=2.6×1015 cm-3). Bu durum mobilite ile taşıyıcı aktivasyonu arasında bir denge olduğuna işaret etmektedir. Bu sonuçlar, CdSeTe/Sb film yapılarında Sb tabakasının kaplanmasından önceki ön-işlemin taşıyıcıların taşınımını ve elektriksel davranışını kritik bir şekilde yönettiğini ve potansiyel fotovoltaik performansı artırma açısından doğrudan etkileri olduğunu göstermektedir.

Anahtar Kelimeler

• CdSeTe/Sb
• ön-işlem
• CdCl2
• termal tavlama
• taşıyıcı konsantrasyonu
• taşıyıcı mobilitesi

Teşekkür

A. Çiriş, finansal destek için Türkiye Bilimsel ve Teknolojik Araştırma Kurumu’na (TÜBİTAK) ve malzeme hazırlama ve karakterizasyon çalışmalarına sağlanan destek için Delaware Üniversitesi Enerji Dönüşümü Enstitüsü’ne (IEC) teşekkür eder.

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