Chromium Trioxide Hole-Selective Heterocontacts for Silicon Solar Cells

Abstract

A high recombination rate and high thermal budget for aluminum (Al) back surface field are found in the industrial p-type silicon solar cells. Direct metallization on lightly doped p-type silicon, however, exhibits a large Schottky barrier for the holes on the silicon surface because of Fermi-level pinning effect. As a result, low-temperature-deposited, dopant-free chromium trioxide (CrO , x< 3) with high stability and high performance is first applied in a p-type silicon solar cell as a hole-selective contact at the rear surface. By using 4 nm CrO between the p-type silicon and Ag, we achieve a reduction of the contact resistivity for the contact of Ag directly on p-type silicon. For further improvement, we utilize a CrO (2 nm)/Ag (30 nm)/CrO (2 nm) multilayer film on the contact between Ag and p-type crystalline silicon (c-Si) to achieve a lower contact resistance (40 mΩ·cm). The low-resistivity Ohmic contact is attributed to the high work function of the uniform CrO film and the depinning of the Fermi level of the SiO layer at the silicon interface. Implementing the advanced hole-selective contacts with CrO /Ag/CrO on the p-type silicon solar cell results in a power conversion efficiency of 20.3%, which is 0.1% higher than that of the cell utilizing 4 nm CrO . Compared with the commercialized p-type solar cell, the novel CrO-based hole-selective transport material opens up a new possibility for c-Si solar cells using high-efficiency, low-temperature, and dopant-free deposition techniques.

Solar photovoltaic panels as next generation waste: a review

“…Using the thin film technology new absorbers are going to use like microcrystalline silicon, cadmium telluride, CIGS etc. These absorbers can bring down the cost of cell but consists of a major drawback which is thin film solar cell are less efficient than crystalline silicon solar cell [32].Chromium is also used nowadays as a chromium trioxide, for hole-selective transport material with a greater efficiency [27] but in the other hand again chromium is a carcinogenic compound for the environment t [9]. Chromium which is a strong oxidizing agent can be an immunotoxic, genotoxic and also be mutagenic for living beings in a high amount.…”

Dopant‐Free Bifacial Silicon Solar Cells

“…Therefore, extensive efforts have been devoted to the improvement of silicon solar cells with dopant‐free passivating contacts. [ 4–9 ] By replacing a‐Si:H(p) with a 4 nm thick hole‐collecting and transparent molybdenum oxide (MoO x ) layer, a remarkable solar cell efficiency of 23.5% was recently demonstrated. [ 10 ] The integration of an a‐Si:H(i)/LiF x /Al electron selective contact at the rear side, instead of a‐Si:H(i)/ a‐Si:H(n)/ITO/Ag, [ 11 ] enabled the development of a fully dopant‐free silicon solar cell without any doped a‐Si:H layers or diffused p–n junctions.…”

“…One approach to realize dopant‐free bifacial silicon solar cells consists of using partial area electron‐selective contacts. [ 2,7,8,19,25 ] In work by Zhong et al, an a‐Si:H(i)/ZnO/LiF x /Al contact exhibited a J 0 of 3.5 fA cm −2 and ρ c of 0.136 Ω cm 2 . [ 12,30 ] In that case, the contact resistance is potentially low to form a partial‐area heterocontact for dopant‐free bifacial silicon solar cells with a metal contact fraction between 10% and 50%.…”

Solution‐Processed Copper‐Doped Chromium Oxide with Tunable Oxygen Vacancy for Crystalline Silicon Solar Cells Hole‐Selective Contacts

“…[ 3 ] At present, most of these TMO materials are fabricated by vacuum deposition, such as high vacuum thermal evaporation, electron beam deposition, and sputtering. [ 17–21 ] However, it is hard to modify intrinsic TMO's electronic properties by doping or annealing in such a vacuum fabrication process. Alternatively, solution‐processed TMO can realize quantity control of dopant and one‐step synthetic annealing process.…”