On-site measurement of limiting subcell in multijunction solar devices

Abstract

Abstract.It is well known that the response of any photovoltaic solar cell is dependent on the spectral characteristics of the incident radiation. This dependency is crucial in the output characteristics of a multijunction (MJ) cell where the spectral composition of the radiation determines the overall photocurrent produced, as either the top or the middle subcell will be limiting its response. The current mismatching between top and middle subcell is translated into energy losses, affecting the yield of the system. For research and commercial purposes it is interesting to measure accurately the incident solar radiation on a MJ cell, in terms of its spectral composition. This measurement will allows us to determine the photocurrent generated in each band of the multijunction device. Nowadays, the only way of measuring the photocurrent generated by each subcell is done with isotype cells or with spectroradiometers but there is no device capable of directly measuring each subcell photocurrent. In this paper it is described a device based on a commercial multijunction solar cell that is capable of measuring the direct irradiance for the top and middle bands thus it offers information of the limiting subcell (top or middle) in outdoors conditions.

Optical component analysis for ultrahigh concentrated photovoltaic system (UHCPV)

“…To theoretically characterise the optical efficiency (η 𝑜𝑝𝑡,𝑡ℎ ) and the concentration ratio (𝐶 𝑡ℎ ), we incorporate the average total transmittance (%𝑇), the geometrical concentration ratio (𝐶 𝑔 ), and the fractional concentration loss (%𝐶) with radiant flux (𝐽) on the receiver area (𝐴 𝑟𝑒𝑐𝑒𝑖𝑣𝑒𝑟 ), and then divided with the radiant flux on the concentrator area (𝐴 𝐹𝑟𝑒𝑠𝑛𝑒𝑙 ), as in Eq.1. For the multi-junction solar cell, the influence of incident spectrum irradiance on the short-circuit current (𝐼 𝑠𝑐 ) to determine the photocurrent generation ratio of the top subcell over the middle subcell (𝐼 𝑇 /𝐼 𝑀 ) should be accountable for in the calculation of the optical efficiency (Fernández, E.F., Almonacid, F., Rodrigo, P.M., Pérez-Higueras, 2017;Muñoz-Cerón et al, 2012). 𝐼 𝑇 /𝐼 𝑀 terms in Eq.1 is only to express that the optical efficiency for the case of a multi-junction cell is driven by the photocurrent generation ratio.…”