Concentrator In2O3:F/(n+pp+)c-Si/Al solar cells with Al-alloyed BSF and Ag-free multi-wire metallization using transparent conductive polymers

Cost-effective low concentrator c-Si-based PV systems have been under development for more than 30 years without any significant commercial break-through. One primary reason for that is the cost and availability of Si cells for such applications. We have developed high efficiency low concentrator crystalline silicon (c-Si) solar cells using the standard SiNx/(n(+)pp(+))c-Si/Al structures with a P-doped n(+)-emitter and screen-printed Al-alloyed Al-p(+) back-surface-field (BSF). Ag-free multi-wire metallization has been applied using transparent conductive polymers. We have investigated seven groups of solar cell structures based on both Cz-Si and mc-Si and produced by the BSF formation processes with various peak firing temperatures (T-F) in a conveyor belt furnace. T-F was varied in the range of 820,940 degrees C in 20 degrees C steps. Surface morphology of the structures has been examined by scanning electron microscope. External quantum efficiency, reflection spectra, sheet resistance, Suns-V-oc and current-voltage dependence under illumination have been studied. The structures obtained at T-F = 860 degrees C have been used for fabrication of low concentrator solar cells based on an indium fluorine oxide (IFO)/(n(+)pp(+))c-Si/Al structure. Transparent conductive IFO films, acting as passivating and antireflection electrodes, were grown by ultrasonic spray pyrolysis. A copper wire contact pattern was attached by low-temperature lamination simultaneously to the front (IFO) and rear (Al) layers using transparent conductive polymer films (laminated grid cell (LGCell) design). The best LGCells from Cz-Si/mc-Si showed an efficiency of 18.3-19.2%/15.9-16.7% in the operating range of 1-12 suns/1-10 suns.