Improvement of the SiO_x Passivation Layer for High-Efficiency Si/PEDOT:PSS Heterojunction Solar Cells

Abstract

Interfacial properties currently hinder the performance of Si/organic heterojunction solar cells for an alternative to high-efficiency and low-cost photovoltaics. Here, we present a simple and repeatable wet oxidation method for developing the surface passivation layer, SiOx, on the Si surface for the fabrication of high-efficiency Si/poly(3,4-ethylene-dioxythiophene):polystyrenesulfonate (PEDOT:PSS) heterojunction solar cells. The uniform and dense SiOx thin layer introduced by the oxidizing aqueous solution of H2O2 or HNO3 provided the better surface passivation and stronger wettability of the Si surface, compared to those in the native oxide case. These two types of progress helped create a lower defect density at the Si/PEDOT:PSS interface and thus a high-quality p-n junction with a lower interface recombination velocity. As a result, the HNO3-oxidized device displayed better performance with a power conversion efficiency (PCE) of 11%, representing a 28.96% enhancement from the PCE of 8.53% in the native oxide case. The effects on the performance of the Si/PEDOT:PSS hybrid solar cells of the wet oxidation treatment procedure, including the differences in surface roughness and wettability of the Si substrate, the quality and thickness of the SiOx, etc., were explored extensively. Such a simple and controllable oxidizing treatment could be an effective way to promote the interfacial properties that are an important cornerstone for more efficient Si/organic hybrid solar cells.

Highly Conductive PEDOT:PSS Transparent Hole Transporting Layer with Solvent Treatment for High Performance Silicon/Organic Hybrid Solar Cells

“…Finally, the samples were immersed in a diluted HF (5%) solution for 5 min to remove the native oxide to obtain H-Si surfaces. The cleaned Si were then transferred into a diluted HNO 3 (10%) solution to form a SiO x film to act as a passivation layer [25,26]. Highly conductive PED-OT:PSS (Clevios PH1000) uniformly mixed with 5 wt% DMSO and 1 wt% Triton X-100 was spin-coated onto the surface of the SiO x -terminated Si substrate at a spin speed of 1500 rpm in air for 60 s. Following that, the samples were annealed at 140°C for 10 min under nitrogen atmosphere.…”

Hole-Transporting Layer Treatment of Planar Hybrid n-Si/PEDOT:PSS Solar Cells with Power Conversion Efficiency up to 14.5%

“…Their high thermal budget accounts for~30% of the total manufacturing cost of silicon (Si) solar cells [2]. To reduce the fabrication cost, the low-temperature solar cell concepts based on the organic/inorganic hybrid heterojunctions, particularly the Si/poly (3,4-ethylenedioxythiophene):-poly(styrenesulfonate) (Si/PEDOT:PSS), have attracted significant research interest in recent years [3][4][5][6]. Si has a strong absorption ability in a very wide spectrum range and very excellent carrier transport ability.…”

“…And PEDOT:PSS is a water-soluble polymer which has high conductivity, a transmission window in the visible spectral range, and an excellent chemical and thermal stability [7]. This type of Si/PEDOT:PSS hybrid solar cell combines the superior absorption property of Si in a wide spectrum range and the advantage of aqueous solution-based processes for PED-OT:PSS [4], which avoids an expensive high-temperature process and promises a low-cost photovoltaic technique with the potential to realize a power conversion efficiency (PCE) as high as 22% in theory [5].…”

Low-Temperature, Chemically Grown Titanium Oxide Thin Films with a High Hole Tunneling Rate for Si Solar Cells

“…Although the a-Si:H-based heterojunction with intrinsic thin-film technology has demonstrated high efficiency, an alternative material that inherently exhibits excellent surface passivation and proper band alignment is required. Therefore, in addition to a-Si:H, metal oxides such as AlO x [11][12][13], SiO 2 [14,15], and TiO 2 [16,17] have been used in constructing carrier selective barriers with passivation ability on crystalline Si to achieve a high photocurrent. Pudasaini et al [11] used ultrathin aluminum oxide (approximately 1.84 nm), grown through an atomic layer deposition, on an n-type Si wafer as a passivation layer in a poly (3,4-ethylenedioxythiophene) polystyrene sulfonate/Si hybrid heterojunction solar cell system.…”

“…Pudasaini et al [11] used ultrathin aluminum oxide (approximately 1.84 nm), grown through an atomic layer deposition, on an n-type Si wafer as a passivation layer in a poly (3,4-ethylenedioxythiophene) polystyrene sulfonate/Si hybrid heterojunction solar cell system. Sheng et al [14] used a wet method to form silicon oxide on a Si wafer as a passivation layer. A 10.48% efficiency was achieved in a hybrid solar cell.…”