Effect of III-nitride polarization on V OC in p-i-n and MQW solar cells

We performed detailed studies of the effect of polarization on III-nitride solar cells. Spontaneous and piezoelectric polarizations were assessed to determine their impacts upon the open circuit voltages (VOC) in p–i(InGaN)–n and multi-quantum well (MQW) solar cells. We found that the spontaneous polarization in Ga-polar p–i–n solar cells strongly modifies energy band structures and corresponding electric fields in a way that degrades VOC compared to non-polar p–i–n structures. In contrast, we found that piezoelectric polarization in Ga-polar MQW structures does not have a large influence on VOC compared to non-polar MQW structures. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)