Recent results for single‐junction and tandem quantum well solar cells

Adams, Jessica G. J.; Browne, Ben; Ballard, Ian; Connolly, J.P.; Chan, Ngai Lam Alvin; Ioannides, Andreas; Elder, Warren J.; Stavrinou, Paul N.; Barnham, K.W.J.; Ekins-Daukes, N. J.

doi:10.1002/pip.1069

Cited by 69 publications

(38 citation statements)

References 46 publications

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“…Strain balanced multi-quantum wells (MQW) are an established method for tailoring the absorption edge of III-V solar cells. Research over the last couple of years has addressed the performance as a function of the position of the QWs inside the device, 1,2 their number, 3,4 their composition to keep them strain-balanced, 5 and the effect of background doping on carrier extraction. 6 As a result of these efforts, InGaP/MQW/Ge quantum well devices have attained efficiencies in excess of 40% under concentration 5 and over 30% under air-mass 0 solar spectrum (AM0).…”

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confidence: 99%

“…Research over the last couple of years has addressed the performance as a function of the position of the QWs inside the device, 1,2 their number, 3,4 their composition to keep them strain-balanced, 5 and the effect of background doping on carrier extraction. 6 As a result of these efforts, InGaP/MQW/Ge quantum well devices have attained efficiencies in excess of 40% under concentration 5 and over 30% under air-mass 0 solar spectrum (AM0). 7 These achievements have required a mastery of the fabrication of strain balanced MQW structures on highly misoriented substrates (typically [100] 6 towards [111]B).…”

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confidence: 99%

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InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

Alonso-Álvarez

Thomas

Führer

et al. 2014

Applied Physics Letters

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Quantum wires (QWRs) form naturally when growing strain balanced InGaAs/GaAsP multi-quantum wells (MQW) on GaAs [100] 6° misoriented substrates under the usual growth conditions. The presence of wires instead of wells could have several unexpected consequences for the performance of the MQW solar cells, both positive and negative, that need to be assessed to achieve high conversion efficiencies. In this letter, we study QWR properties from the point of view of their performance as solar cells by means of transmission electron microscopy, time resolved photoluminescence and external quantum efficiency (EQE) using polarised light. We find that these QWRs have longer lifetimes than nominally identical QWs grown on exact [100] GaAs substrates, of up to 1 μs, at any level of illumination. We attribute this effect to an asymmetric carrier escape from the nanostructures leading to a strong 1D-photo-charging, keeping electrons confined along the wire and holes in the barriers. In principle, these extended lifetimes could be exploited to enhance carrier collection and reduce dark current losses. Light absorption by these QWRs is 1.6 times weaker than QWs, as revealed by EQE measurements, which emphasises the need for more layers of nanostructures or the use light trapping techniques. Contrary to what we expected, QWR show very low absorption anisotropy, only 3.5%, which was the main drawback a priori of this nanostructure. We attribute this to a reduced lateral confinement inside the wires. These results encourage further study and optimization of QWRs for high efficiency solar cells.

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confidence: 99%

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confidence: 99%

InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

Alonso-Álvarez

Thomas

Führer

et al. 2014

Applied Physics Letters

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“…For example, strain-balanced quantum wells (QW) or quantum dots (QD) can be used to effectively lower the bandgap, and single-junction cell efficiencies of over 28% under concentration has been achieved via this approach [23].…”

Section: Nanostructures For Bandgap Engineeringmentioning

confidence: 99%

Photovoltaic Devices

Ringel

Anderson

Green

et al. 2013

Guide to State‐of‐the‐Art Electron Devices

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“…As discussed before, for a 3J device with a germanium bottom cell, an optimum band gap combination under AM1.5D solar spectrum at 1000 suns would be around 1.19 eV -1.75 eV for the middle -top cells, respectively (Figure 1). However, Browne et al showed that the optimum bandgap in a QW solar cell was indeed dependent on the quantum efficiency of the QWs, being higher if that efficiency was below certain value 1 . As we will discuss in the next section, although the quantum efficiency (QE) of a MQW structure can reach up to 75%, state of the art MQW solar cells have more often values between 40%-60%.…”

Section: Target Performance For Maximum Efficiencymentioning

confidence: 99%

“…The most successful application of this technique was a GaAs, single junction device with multiple InGaAs/GaAsP quantum wells, that had an efficiency of 28.3% under AM1.5D 416 X, breaking a 20-year long world record for single junction devices 1 . More recent research in this field has already produced dual-junction devices with efficiencies close to their bulk counterparts (30.6% compared to 31.7%).…”

Section: Historic Perspectivementioning

confidence: 99%

Quantum wells for high-efficiency photovoltaics

Alonso-Álvarez

Ekins-Daukes

2016

SPIE Proceedings

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Over the last couple of decades, there has been an intense research on strain balanced semiconductor quantum wells (QW) to increase the efficiency of multi-junction solar (MJ) solar cells grown monolithically on germanium. So far, the most successful application of QWs have required just to tailor a few tens of nanometers the absorption edge of a given subcell in order to reach the optimum spectral position. However, the demand for higher efficiency devices requiring 3, 4 or more junctions, represents a major difference in the challenges QWs must face: tailoring the absorption edge of a host material is not enough, but a complete new device, absorbing light in a different spectral region, must be designed. Among the most important issues to solve is the need for an optically thick structure to absorb enough light while keeping excellent carrier extraction using highly strained materials. Improvement of the growth techniques, smarter device designs -involving superlattices and shifted QWs, for example -or the use of quantum wires rather than QWs, have proven to be very effective steps towards high efficient MJ solar cells based on nanostructures in the last couple of years. But more is to be done to reach the target performances. This work discusses all these challenges, the limitations they represent and the different approaches that are being used to overcome them.

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Recent results for single‐junction and tandem quantum well solar cells

Cited by 69 publications

References 46 publications

InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

Photovoltaic Devices

Quantum wells for high-efficiency photovoltaics

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