Abstract
Nowadays, the multi-crystalline silicon (mc-Si) solar cells dominate the photovoltaic industry. However, the current acid etching method on mc-Si surface used by firms can hardly suppress the average reflectance value below 25% in the visible light spectrum. Meanwhile, the nitric acid and the hydrofluoric contained in the etching solution is both environmental unfriendly and highly toxic to human. Here, a mc-Si solar cell based on ZnO nanostructures and an Al2O3 spacer layer is demonstrated. The eco-friendly fabrication is realized by low temperature atomic layer deposition of Al2O3 layer as well as ZnO seed layer. Moreover, the ZnO nanostructures are prepared by nontoxic and low cost hydro-thermal growth process. Results show that the best passivation quality of the n+ -type mc-Si surface can be achieved by balancing the Si dangling bond saturation level and the negative charge concentration in the Al2O3 film. Moreover, the average reflectance on cell surface can be suppressed to 8.2% in 400–900 nm range by controlling the thickness of ZnO seed layer. With these two combined refinements, a maximum solar cell efficiency of 15.8% is obtained eventually. This work offer a facile way to realize the environmental friendly fabrication of high performance mc-Si solar cells.
Highlights
To efficiently suppress the optical reflection losses, the Si nanostructures (NS) formed by metal-catalyzedetching (MCE)[6,7,8], laser ablation[9,10] and reactive-ion-etching (RIE)[5,11,12,13,14] on multi-crystalline silicon (mc-Si) substrates have been proposed, which can achieve
A lowest average reflectance of 8.5% in 400~900 nm range can be achieved, leading to an increased solar cell performance in Jsc of 4.2 mA/cm[2]. Based on this hierarchical structure, a maximum conversion efficiency (CE) value of 15.8% is obtained for the optimized mc-Si solar cell, which has a comparable performance to the previously reported single crystalline silicon (sc-Si) cell based on ZnO NS with a highest CE of 16.0%34
To realize the best passivation quality of the Al2O3 film, the minority carrier lifetime (τ) on the 70 Ω per square n+ doped mc-Si surface are investigated as a function of the Al2O3 film thickness as well as the annealing duration of the Al2O3/mc-Si stacks
Summary
To efficiently suppress the optical reflection losses, the Si nanostructures (NS) formed by metal-catalyzedetching (MCE)[6,7,8], laser ablation[9,10] and reactive-ion-etching (RIE)[5,11,12,13,14] on mc-Si substrates have been proposed, which can achieve
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