Abstract
Photovoltaic devices based on amorphous silicon/crystalline silicon (a-Si:H/c-Si) heterojunction interfaces hold the highest efficiency as of date in the class of silicon-based devices with efficiencies exceeding 26% and are regarded as a promising technology for large-scale terrestrial PV applications. The detailed understanding behind the operation of this type of device is crucial to improving and optimizing its performance. SHJ solar cells have primarily two main interfaces that play a major role in their operation: the transparent conductive oxide (TCO)/a-Si:H interface and the a-Si:H/c-Si heterojunction interface. In the work presented here, a detailed analytical description is provided for the impact of both interfaces on the performance of such devices and especially on the device fill factor ( FF ). It has been found that the TCO work function can dramatically impact the FF by introducing a series resistance element in addition to limiting the forward biased current under illumination causing the well-known S-shape characteristic in the I-V curve of such devices. On the other hand, it is shown that the thermionic emission barrier at the heterojunction interface can play a major role in introducing an added series resistance factor due to the intrinsic a-Si:H buffer layer that is usually introduced to improve surface passivation. Theoretical explanation on the role of both interfaces on device operation based on 1D device simulation is experimentally verified. The I-V characteristics of fabricated devices were compared to the curves produced by simulation, and the observed degradation in the FF of fabricated devices was explained in light of analytical findings from simulation.
Highlights
Solar cell devices based on hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) heterojunction (SHJ) experience relatively high open-circuit voltages (VOC) and short-circuit currents (JSC) leading to high conversion efficiencies (η) exceeding 26% when combined with Interdigitated Back Contact (IBC) technology [1]
International Journal of Photoenergy discontinuities in the presence of chemical passivation that is achieved due to the high-quality interface between the c-Si substrate and the a-Si:H(i) layer [6, 7]. It has been elucidated by Ghannam et al that if the inversion layer carrier density is severely impacted, the SHJ device performance will deteriorate despite the fact that high chemical passivation is present due to the a-Si:H(i) buffer layer
The SHJ device comprises of two main interfaces, namely, the transparent conductive oxide (TCO)/a-Si:H interface and the a-Si:H/c-Si interface
Summary
Solar cell devices based on hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) heterojunction (SHJ) experience relatively high open-circuit voltages (VOC) and short-circuit currents (JSC) leading to high conversion efficiencies (η) exceeding 26% when combined with Interdigitated Back Contact (IBC) technology [1]. Reduced optical losses at the front side attributed to the IBC architecture and the relatively low recombination losses attributed to the high passivation quality of the SHJ (a-Si:H/c-Si) interfaces have been accredited as the main reasons behind such a high efficiency Such structures build upon the improved emitter efficiency of a-Si:H/c-Si bipolar transistors [2] and original solar cells with the so-called heterojunction with intrinsic thin layer (HIT®) developed by the Sanyo group in 1992 [3]. International Journal of Photoenergy discontinuities in the presence of chemical passivation that is achieved due to the high-quality interface between the c-Si substrate and the a-Si:H(i) layer [6, 7] It has been elucidated by Ghannam et al that if the inversion layer carrier density is severely impacted, the SHJ device performance will deteriorate despite the fact that high chemical passivation is present due to the a-Si:H(i) buffer layer. The presence of this inversion layer inside the c-Si substrate close to the a-Si:H/cSi interface has been experimentally verified and examined in the past [8,9,10]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
