First-principles Design of AM2Pn2 Alloys for Top Cell Absorbers in Tandem Photovoltaics

Zintl phosphides BaCd₂P₂ and CaZn₂P₂ have recently emerged as promising solar absorbers, showing suitable band gaps, good stability, and long carrier lifetime [1,2].CaZn₂P₂ has also been synthesized as a thin film at a low processing temperature In this talk, we explore the entire class of AM₂Pn₂ compounds, with A=Ba, Sr, Ca, Yb, Mg; M=Mn, Mg, Cd, Zn; Pn= Bi, Sb, As, P, N, and study their thermodynamic stability and electronic properties using first-principles calculations. We find that most of these materials are thermodynamically stable in the same crystal structure as each other and their band gaps span quite a wide range (0–3.2 eV). We next focus on the AM₂Pn₂ materials with band gaps suitable for absorbers in the top cell of tandem devices. To design top cell absorbers, we explore tuning for optimal bandgaps by alloying AM₂Pn₂ compounds and suggest promising combinations for tandem solar cells. We will also discuss computational methods to screen for stable and desirable alloys in a high throughput fashion.

[1] Yuan, Z., Dahliah, D., Hasan, M. R., Kassa, G., Pike, A., Quadir, S., Claes, R., Chandler, C., Xiong, Y., Kyveryga, V., Yox, P., Rignanese, G. M., Dabo, I., Zakutayev, A., Fenning, D. P., Reid, O. G., Bauers, S., Liu, J., Kovnir, K., & Hautier, G. (2024). Discovery of the Zintl-phosphide BaCd2P2 as a long carrier lifetime and stable solar absorber. Joule, 8(5), 1412–1429. https://doi.org/10.1016/j.joule.2024.02.017

[2] Quadir, S., Yuan, Z., Esparza, G. L., Dugu, S., Mangum, J. S., Pike, A., Hasan, M. R., Kassa, G., Wang, X., Coban, Y., & others. (2024). Low-Temperature Synthesis of Stable CaZn2P2 Zintl Phosphide Thin Films as Candidate Top Absorbers. Advanced Energy Materials, 2402640.