Technical Papers

Finance | The emerging solar markets of Southeast Asia each present their own unique set of conditions from a financing perspective. Reporting back from the Solar Finance & Investment Southeast Asia conference in Thailand at the end of 2016, Tom Kenning looks at how a promising solar region is bringing in the investors.

System integration | Taiwan has set itself a target of 20GW of PV by 2025, but standing in the way of that are acute land shortages and some extreme weather conditions. Tom Kenning reports on the creative technological and construction solutions being found to address Taiwan’s unique challenges.

Operations & maintenance | Proposals by Chinese authorities to scale back the subsidies available for grid-tied PV will require new efforts to maximise the performance of power plants. Karl Hong Wan of the GCL Design & Research Institute explores some of the innovations in O&M practices that will help China’s solar industry cope with decreasing financial support.

This paper presents an in-depth analysis of state-of-the-art p-type monocrystalline Czochralski-grown silicon passivated emitter and rear cells (PERCs) fabricated in a near-industrial manner. PERC solar cells feature a homogeneous emitter on the front side, and an Al2O3 passivation layer and local contacts on the rear side.

Even though it is now more than five years since potential-induced degradation (PID) began to proliferate, and despite the fact that solutions are under development, it is currently still the most discussed mode of degradation associated with cracking in PV modules.

Conventional ribbons used for interconnecting solar cells in PV modules act like mirrors, causing a large proportion of incident light to be lost. Experimental results indicate that only around 5% of the perpendicular incident light on the connections can be reused; as a result, this area contributes very little, if at all, to the current generation.

A highly promising concept for future solar cells is the heterojunction (HJT) architecture; according to the ITRPV roadmap 2016, the market share for HJT solar cells will increase to 10% by 2026. Over this timescale, stabilized cell efficiency will increase to 24%, which is the second-highest predicted efficiency after backcontact cells with n-type mono-Si. Moreover, metallization of HJT cells offers the advantage of using low-temperature steps, which reduces energy consumption and hence production costs.

This paper presents the fabrication of front-junction n-type silicon solar cells with Cu-plated electrodes, using laser contact opening and forward-bias plating. The cells feature a back-surface field formed by a phosphorus implant, and a diffused boron emitter with aluminium oxide passivation. Laser ablation of the front-side dielectric layers is followed by a metallization based on Ni/Cu forward-bias plating, while sintered metal paste is used for the rear electrode. The results show improved line conductivity and contact resistivity for the plated electrode, leading to higher solar cell efficiency than for cells made with conventional Ag/Al paste. On 6" n-type Czochralski wafers, cell efficiencies of up to 21.3% have been demonstrated, with an open-circuit voltage of 654mV, a short-circuit current of 40.8mA/cm2 and a fill factor of 79.8%.

Perovskite microcrystals have properties that make them uniquely suitable as a basis of thin, light, semitransparent solar modules. However, there are some remaining challenges, including lifelong stability, that need to be tackled before this technology can become commercially available.

Project finance - Minimising risk to lenders is vital in ensuring the solar industry continues to have access to adequate sources of finance. Simon Turner and Paola Piazzolla outline the key ingredients for the technical due diligence needed to give peace of mind to investors.