Improvement of silicon heterojunction solar cell performance with new surface structure and wide band gap carrier selective layers

2021-10-15
Dönerçark, Ergi
The photovoltaic (PV) industry is dominated by silicon-based solar cells owing to the abundance of silicon and its full-fledged technology. The main road for the PV industry points out to enhance the conversion efficiency of solar cells while decreasing production costs, which is crucial for improving renewable energy market share. The silicon heterojunction solar cells (SHJ) are receiving attention on this road map due to their higher conversion efficiencies, simple process flow, and low-temperature fabrication sequence. In order to further enhance the SHJ device performance, both electrical and optical properties should be improved simultaneously. In this Ph.D. thesis work, various aspects of SHJ solar cells, such as surface texturing, surface passivation, and material choices, were addressed. Firstly, surface texturing was studied to search for new approaches to reduce optical losses. Even though the well-established surface texturing method generating random pyramids on the surface reduces the reflection successfully, there is still room for improvement. A new and novel silicon surface texturing method based on copper-assisted chemical etching was developed for efficient light management on the surface. With this technique, tetragonal-star shaped inverted pyramids were formed, resulting in extremely low reflectance values. Secondly, the surface passivation of silicon was studied using different process conditions and material systems. The SHJ solar cell performance was significantly improved by understanding the chemical passivation kinetics and improving the surface passivation quality. Thirdly, wide band gap materials were integrated into the SHJ solar cell structure to decrease parasitic absorption losses. Furthermore, the free-carrier absorption losses were reduced significantly by tuning TCO's electrical and optical properties. Based on the theoretical and experimental explanations, the novel method for light trapping and integration of wide band gap materials to SHJ solar cell structure were shown to offer promising alternatives to existing technologies for future applications. With these new material systems and process improvements, we have achieved high-efficiency values of up to 21.2% in the SHJ solar cells fabricated at ODTÜ-GÜNAM.

Suggestions

Analysis of boron doped hydrogenated amorphous silicon carbide thin film for silicon heterojunction solar cells
Salimi, Arghavan; Turan, Raşit; Department of Micro and Nanotechnology (2019)
Silicon based solar cells are the dominant type of solar cells in the photovoltaic industry. Recently, there have been increasing efforts to develop c-Si solar cells with higher efficiency and lower cost. Among them, silicon heterojunction solar cell (SHJ) is attracting much attention because of its superior performance values demonstrated at both R&D and industrial levels. One of the common limiting criteria is the recombination at the front side which can be solved by providing proper passivation at the f...
Optimization of fabrication steps for n-type c-Si solar cells
Orhan, Efe; Ünalan, Hüsnü Emrah; Department of Metallurgical and Materials Engineering (2019)
Crystalline silicon (c-Si) solar cells fabricated on p-type wafers are still dominating the photovoltaic (PV) industry due to advantages in device processing and early focus on p-type cells in the development phase of the industry. Over the years, studies on n-type Czochralski (CZ) substrates have shown that they can be more desirable for the terrestrial applications due to superior material and process advantages such as higher minority carrier lifetime, easier passivation of the surface, absence of light ...
Optimization of laser processing for PERC type c-Si solar cells
Genç, Ezgi; Turan, Raşit; Department of Micro and Nanotechnology (2019)
Passivated Emitter Rear Contact (PERC) type solar cells, which currently owns a similar market share as the standard type solar cells, is expected to be the dominant type of the photovoltaic (PV) market in near future (ITRPV, 2019) due to its high performance/cost ratio. Hence, it is critical to optimize PERC process steps to achieve higher efficiencies. In PERC concept, the stack of a passivation layer and SiNx capping layer is locally ablated to form low recombination and low resistive contacts. In this w...
Simulation of an efficient silicon heterostructure solar cell concept featuring molybdenum oxide carrier-selective contact
MEHMOOD, Haris; NASSER, Hisham; Tauqeer, Tauseef; HUSSAIN, Shahzad; Ozkol, Engin; Turan, Raşit (2018-03-25)
Transition metal oxides/silicon heterocontact solar cells are the subject of intense research efforts owing to their simpler processing steps and reduced parasitic absorption as compared with the traditional silicon heterostructure counterparts. Recently, molybdenum oxide (MoOx, x<3) has emerged as an integral transition metal oxide for crystalline silicon (cSi)-based solar cell based on carrier-selective contacts (CSCs). In this paper, we physically modelled the CSC-based cSi solar cell featuring MoOx/intr...
OPTIMIZATION OF EMITTER LAYER IN N-TYPE BIFACIAL CRYSTALLINE SOLAR CELL
Salimi, Yasaman; Turan, Raşit; Ünalan, Hüsnü Emrah; Department of Micro and Nanotechnology (2022-5-09)
P-type solar cells currently hold most of the market share in industrial solar cell fabrication statistics. NREL's highest efficiency record for p-type crystalline perc cells is 22.8%. However, there is an ever-increasing interest in n-type wafers due to the many advantages they have against p-type cells. According to the ITRPV's estimation, the n-type cell structures will be taking half the industry's share by 2031. Compared to p-type cells, n-type cells yield better efficiency and lifetime values and are ...
Citation Formats
E. Dönerçark, “Improvement of silicon heterojunction solar cell performance with new surface structure and wide band gap carrier selective layers,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.