1. Project Introduction

Developing renewable clean energy is the fundamental way to achieve the Paris climate agreement and has become the consensus of most countries in the world. Photovoltaic power generation occupies a core position in renewable energy. As the era of affordable photovoltaic Internet access gradually approaches, a large number of developed and developing countries have formulated photovoltaic development planning roadmaps. In the next two to three decades, the photovoltaic industry will still have huge development prospects. However, in recent years, due to the leapfrog development of photovoltaic technology, efficiency has been significantly improved, and domestic industrial policies have been adjusted, competition among photovoltaic companies has intensified. There is an urgent need for new technologies to improve efficiency, reduce costs, and enhance competitiveness.

It is internationally recognized that the limit efficiency of Passived contact technology is 1.5% higher than that of the current mainstream Passived emitter and back contact (PERC) technology. It is a next-generation high-efficiency battery structure for industrialization, as shown in Figure 1(a). Tunneling Oxygen Passivation Contact (TOPCon) is a technology with unique advantages in the passivation contact family: it is highly compatible with existing technologies, and only needs to add 2-3 core equipment to upgrade existing production lines. It is achieved While significantly improving efficiency, it does not require much capital investment, so it has attracted great attention from academia and industry and is considered one of the technologies with the most industrial application prospects. The successful development of the next generation of efficient TOPCon technology will help companies occupy the commanding heights of the next round of development. At present, several of China's largest photovoltaic companies, such as Jingke, Tianhe, Jingao, Zhonglai, Dongfang Risheng, etc., are already developing TOPCon technology. Most other battery manufacturing companies and equipment manufacturing companies with R & D capabilities also have plans to carry out relevant research.

2. Cooperation content

(1) Brief introduction of the main relevant technologies involved

Mainstream PERC technology achieves surface passivation through aluminum oxide/silicon nitride, while simultaneously achieving carrier collection through local contact between metal electrodes and silicon. This makes this technology have two limiting factors in terms of efficiency improvement: first, there is a certain proportion of metal/silicon highly complex areas on the surface, which limits the improvement of passivation indicators; second, local electrode contact increases the transport distance and recombination of carriers. probability, which limits the improvement of fill factor (FF). TOPCon technology uses ultra-thin silicon oxide and heavily doped silicon films to achieve high-quality passivation and selective carrier collection on the full backside, completely avoiding contact between metal and silicon, and significantly improving passivation and contact performance.

Single-sided saturation current density (J0) is the core indicator for evaluating passivation effect. The lower the value, the better the passivation effect. The J0 of PERC technology is around 60-90fA/cm2, while the J0 of TOPCon is below 10 fA/cm2. Due to improved passivation, the expected efficiency of TOPCon cells is around 25%, which is 1.5% higher than that of PERC cells. In addition, the TOPCon structure also adopts a one-dimensional carrier transmission and collection structure, which is simple and reliable, does not require laser opening, and is highly compatible with existing production lines. Therefore, TOPCon is widely regarded as the standard structure for the next generation of high-efficiency crystalline silicon batteries for industrial use.

(2) Proposed cooperation areas and partners

In 2018, the world's new installed photovoltaic capacity reached more than 90GW, with a total output value of more than 400 billion yuan. Currently, passivated emitter and back technology (PERC) has become a mainstream technology. If you want to continue to improve battery efficiency, using passivated contact technology is an inevitable choice, as shown in Figure 1(a). Currently, there are two passivation contact technologies on the market, one is silicon heterojunction (HIT or SHJ), and the other is TOPCon. The difference between the two technologies is that HIT technology requires re-purchasing the production line, while TOPCon technology can be obtained by upgrading the existing PERC production line. As a result, TOPCon technology has become the best choice for many existing PERC battery manufacturers. Developing TOPCon technology or TOPCon core equipment can directly serve photovoltaic manufacturing companies and open up hundreds of billions of markets, which has great economic value.

(3) Proposed cooperation model

Technical consultation, technical services, technical commissioning, technology development, technology transfer, technology licensing, industrialization