Damp-Heat Induced Performance Degradation for InGaP/GaAs/Ge Triple-Junction Solar Cell

Hwen-Fen Hong,Yen-Yeh Chen,Wu-Yih Uen,Tsung-Shiew Huang

doi:10.1155/2014/410717

Abstract

We performed accelerated tests on sealed and nonsealed InGaP/InGaAs/Ge triple-junction (TJ) solar cells in a complex high temperature and high humidity environment and investigated the electrical properties over time. The degradation of energy conversion efficiency in nonsealed cells was found to be more serious than that in sealed cells. The short-circuit current (ISC), open-circuit voltage (VOC), and fill factor (FF) of sealed cells changed very slightly, though the conversion efficiency decreased 3.6% over 500 h of exposure. This decrease of conversion efficiency was suggested to be due to the deterioration of silicone encapsulant. TheISC,VOC, and FF of nonsealed cells decreased with increasing exposure time. By EL and SEM analysis, the root causes of degradation can be attributed to the damage and cracks near the edge of cells induced by the moisture ingress. It resulted in shunt paths that lead to a deterioration of the conversion efficiency of solar cell by increasing the leakage current, as well as decreasing open-circuit voltage and fill factor of nonsealed solar cells.

Highlights

TJ solar cells are fabricated using organometallic vapor phase epitaxy (OMVPE) to deposit subcells of GaInP and GaInAs on Ge substrate [1]
It resulted in shunt paths that lead to a deterioration of the conversion efficiency of solar cell by increasing the leakage current, as well as decreasing open-circuit voltage and fill factor of nonsealed solar cells
III–V TJ solar cells, with demonstrated efficiency over 40% since 2007 [8], strongly reduce the cost of concentrator photovoltaic (CPV) systems and make III–V multijunction concentrator cells the technology of choice for most concentrator systems today

Summary

Introduction

TJ solar cells are fabricated using organometallic vapor phase epitaxy (OMVPE) to deposit subcells of GaInP and GaInAs on Ge substrate [1]. A TJ solar cell consists of three individual subcells that are stacked on top of each other to form a series connection. The individual subcells are connected to each other through very thin tunnel junction film of several nanometers. These tunnel junctions are typically very thin to allow the tunneling mechanism to dominate the majority carrier transport [2]. TJ solar cells have attracted increasing attention owing to their very high conversion efficiencies [3, 4] as well as long term stability [5,6,7]. The world’s highest energy conversion efficiency solar cells with 44.7% have been demonstrated on June 2013 [9]. The III–V TJ solar cells have nanoscale thin films which can take good advantage of solar light from 300 nm to 1800 nm

Objectives

Results

Conclusion