Anisotropic emission and photon-recycling in strain-balanced quantum well solar cells

Strain-balanced quantum well solar cells (SB-QWSCs) extend the photon absorption edge beyond that of bulk GaAs by incorporation of quantum wells in the i-region of a p i n device. Anisotropy arises from a splitting of the valence band due to compressive strain in the quantum wells, suppressing a transition which contributes to emission from the edge of the quantum wells. We have studied both the emission light polarized in the plane perpendicular (TM) to the quantum well which couples exclusively to the light hole transition and the emission polarized in the plane of the quantum wells (TE) which couples mainly to the heavy hole transition. It was found that the spontaneous emission rates TM and TE increase when the quantum wells are deeper. The addition of a distributed Bragg reflector can substantially increase the photocurrent while decreasing the radiative recombination current. We have examined the impact of the photon recycling effect on SB-QWSC performance. We have optimized SB-QWSC design to achieve single junction efficiencies above 30%.The authors wish to thank the support of CONACYT and COZCYT through project Fomix ZAC-2011-C01-172470.Cabrera, C.; Rimada, J.; Hernandez, L.; Connolly, JP.; Enciso, A.; Contreras-Solorio, DA. (2014). Anisotropic emission and photon-recycling in strain-balanced quantum well solar cells. Journal of Applied Physics. 115(16):164502-1-164502-7. https://doi.org/10.1063/1.4873171164502-1164502-711516Johnson, D. C., Ballard, I. M., Barnham, K. W. J., Mazzer, M., Tibbits, T. N. ., Roberts, J. S., … Calder, C. (2006). Optimisation of Photon Recycling Effects in Strain-Balanced Quantum Well Solar Cells. 2006 IEEE 4th World Conference on Photovoltaic Energy Conference. doi:10.1109/wcpec.2006.279338Ekins-Daukes, N. (2001). Strained and strain-balanced quantum well devices for high-efficiency tandem solar cells. Solar Energy Materials and Solar Cells, 68(1), 71-87. doi:10.1016/s0927-0248(00)00346-9Cabrera, C. I., Rimada, J. C., Connolly, J. P., & Hernandez, L. (2013). Modelling of GaAsP/InGaAs/GaAs strain-balanced multiple-quantum well solar cells. Journal of Applied Physics, 113(2), 024512. doi:10.1063/1.4775404Adams, J. G. J., Browne, B. C., Ballard, I. M., Connolly, J. P., Chan, N. L. A., Ioannides, A., … Ekins-Daukes, N. J. (2011). Recent results for single-junction and tandem quantum well solar cells. Progress in Photovoltaics: Research and Applications, 19(7), 865-877. doi:10.1002/pip.1069J. G. J. Adams, W. Elder, P. N. Stavrinou, J. S. Roberts, M. Gonzalez, J. G. Tischler, R. J. Walters, J. Abell, I. Vurgaftman, J. Meyer, P. Jenkins, K. W. J. Barnham, and N. J. Ekins-Daukes, in Proceedings of the 35th IEEE Photovoltaic Specialists' Conference (2010), pp. 1–5.Connolly, J. P. (s. f.). Analytical Models of Bulk and Quantum Well Solar Cells and Relevance of the Radiative Limit. Advances in Chemical and Materials Engineering, 59-77. doi:10.4018/978-1-4666-1927-2.ch005Johnson, D. C., Ballard, I. M., Barnham, K. W. J., Connolly, J. P., Mazzer, M., Bessière, A., … Roberts, J. S. (2007). Observation of photon recycling in strain-balanced quantum well solar cells. Applied Physics Letters, 90(21), 213505. doi:10.1063/1.2742334Singh, J. (2003). Electronic and Optoelectronic Properties of Semiconductor Structures. doi:10.1017/cbo9780511805745Tsui, E., Nelson, J., Barnham, K., Button, C., & Roberts, J. S. (1996). Determination of the quasi‐Fermi‐level separation in single‐quantum‐wellp‐i‐ndiodes. Journal of Applied Physics, 80(8), 4599-4603. doi:10.1063/1.363442Rimada, J. C., Hernandez, L., Connolly, J. P., & Barnham, K. W. J. (2005). Quantum and conversion efficiency calculation of AlGaAs/GaAs multiple quantum well solar cells. physica status solidi (b), 242(9), 1842-1845. doi:10.1002/pssb.200461764Mathieu, H., Lefebvre, P., & Christol, P. (1992). Simple analytical method for calculating exciton binding energies in semiconductor quantum wells. Physical Review B, 46(7), 4092-4101. doi:10.1103/physrevb.46.4092Courel, M., Rimada, J. C., & Hernández, L. (2012). An approach to high efficiencies using GaAs/GaInNAs multiple quantum well and superlattice solar cell. Journal of Applied Physics, 112(5), 054511. doi:10.1063/1.4749418Johnson, D. C., Ballard, I., Barnham, K. W. J., Bishnell, D. B., Connolly, J. P., Lynch, M. C., … Roberts, J. S. (2005). Advances in Bragg stack quantum well solar cells. Solar Energy Materials and Solar Cells, 87(1-4), 169-179. doi:10.1016/j.solmat.2004.09.01