Voltage Loss Comparison in CdSe/CdTe Solar Cells and Polycrystalline CdSeTe Heterostructures
Cd(Se)Te solar cells have considerable headroom to increase voltage. Voltage losses occur due to incomplete absorption above bandgap E_g and band tail absorption below E_g; such losses are quantified using radiative voltage. The largest voltage losses are attributed to nonradiative recombination, which is quantified via carrier lifetime and radiative efficiency. We compare radiative voltage, radiative efficiency, and carrier lifetime for Cu-doped CdSe/CdTe solar cells and for undoped polycrystalline CdSeTe heterostructures passivated with Al_2O_3. Using external quantum efficiency spectrum and a CdSeTe absorption spectrum obtained from absolute photoluminescence (PL), we show that the radiative voltage is greater than 1.1 V. Time-resolved PL experiments and modeling show that a major part of voltage losses can be attributed to recombination in the absorber bulk. The front interface recombination makes a larger impact within the first few nanoseconds after pulsed excitation, and the comparison of time-gated and time-integrated PL can be used to assess relative contributions of front interface and bulk recombination rates.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- Grant/Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1832225
- Report Number(s):
- NREL/JA-5900-80318; MainId:42521; UUID:0c9c3cd2-5016-4f2a-8c2e-bbec14c45300; MainAdminID:63299
- Journal Information:
- IEEE Journal of Photovoltaics, Vol. 12, Issue 1; ISSN 2156-3381
- Publisher:
- IEEECopyright Statement
- Country of Publication:
- United States
- Language:
- English
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