Effects on Amorphous Silicon Photovoltaic Performance from High-temperature Annealing Pulses in Photovoltaic Thermal Hybrid Devices

TL;DR

This study explores high-temperature annealing of amorphous silicon photovoltaic cells within PVT systems, demonstrating a 10.6% energy gain by reversing light-induced degradation through experimental annealing cycles.

Contribution

It introduces a novel approach of using high-temperature annealing cycles directly on a-Si:H PV cells in PVT systems to mitigate degradation and improve efficiency.

Findings

Annealing at 100°C for 1 hour can reverse degradation effects.

A 10.6% energy gain was observed after annealing cycles.

The method suggests potential for more efficient PVT systems.

Abstract

There is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems, which harvest solar energy for heat and electricity. Typically, a main focus of a PVT system is to cool the photovoltaic (PV) cells to improve the electrical performance, however, this causes the thermal component to under-perform compared to a solar thermal collector. The low temperature coefficients of amorphous silicon (a-Si:H) allow for the PV cells to be operated at higher temperatures and are a potential candidate for a more symbiotic PVT system. The fundamental challenge of a-Si:H PV is light-induced degradation known as the Staebler-Wronski effect (SWE). Fortunately, SWE is reversible and the a-Si:H PV efficiency can be returned to its initial state if the cell is annealed. Thus an opportunity exists to deposit a-Si:H directly on the solar thermal absorber plate where the cells could reach the high temperatures required for annealing. In this study, this opportunity is explored experimentally. First a-Si:H PV cells were annealed for 1 hour at 100\degreeC on a 12 hour cycle and for the remaining time the cells were degraded at 50\degreeC in order to simulate stagnation of a PVT system for 1 hour once a day. It was found that, when comparing the cells after stabilization at normal 50\degreeC degradation, this annealing sequence resulted in a 10.6% energy gain when compared to a cell that was only degraded at 50\degreeC.